]]>
]]>

Latest MySQL Performance Blog posts

You are here

Subscribe to Latest MySQL Performance Blog posts feed
Percona's MySQL & InnoDB performance and scalability blog
Updated: 39 min 59 sec ago

Errant transactions: Major hurdle for GTID-based failover in MySQL 5.6

May 19, 2014 - 12:00am

I have previously written about the new replication protocol that comes with GTIDs in MySQL 5.6. Because of this new replication protocol, you can inadvertently create errant transactions that may turn any failover to a nightmare. Let’s see the problems and the potential solutions.

In short
  • Errant transactions may cause all kinds of data corruption/replication errors when failing over.
  • Detection of errant transactions can be done with the GTID_SUBSET() and GTID_SUBTRACT() functions.
  • If you find an errant transaction on one server, commit an empty transaction with the GTID of the errant one on all other servers.
  • If you are using a tool to perform the failover for you, make sure it can detect errant transactions. At the time of writing, only mysqlfailover and mysqlrpladmin from MySQL Utilities can do that.
What are errant transactions?

Simply stated, they are transactions executed directly on a slave. Thus they only exist on a specific slave. This could result from a mistake (the application wrote to a slave instead of writing to the master) or this could be by design (you need additional tables for reports).

Why can they create problems that did not exist before GTIDs?

Errant transactions have been existing forever. However because of the new replication protocol for GTID-based replication, they can have a significant impact on all servers if a slave holding an errant transaction is promoted as the new master.

Compare what happens in this master-slave setup, first with position-based replication and then with GTID-based replication. A is the master, B is the slave:

# POSITION-BASED REPLICATION # Creating an errant transaction on B mysql> create database mydb; # Make B the master, and A the slave # What are the databases on A now? mysql> show databases like 'mydb'; Empty set (0.01 sec)

As expected, the mydb database is not created on A.

# GTID-BASED REPLICATION # Creating an errant transaction on B mysql> create database mydb; # Make B the master, and A the slave # What are the databases on A now? mysql> show databases like 'mydb'; +-----------------+ | Database (mydb) | +-----------------+ | mydb | +-----------------+

mydb has been recreated on A because of the new replication protocol: when A connects to B, they exchange their own set of executed GTIDs and the master (B) sends any missing transaction. Here it is the create database statement.

As you can see, the main issue with errant transactions is that when failing over you may execute transactions ‘coming from nowhere’ that can silently corrupt your data or break replication.

How to detect them?

If the master is running, it is quite easy with the GTID_SUBSET() function. As all writes should go to the master, the GTIDs executed on any slave should always be a subset of the GTIDs executed on the master. For instance:

# Master mysql> show master status\G *************************** 1. row *************************** File: mysql-bin.000017 Position: 376 Binlog_Do_DB: Binlog_Ignore_DB: Executed_Gtid_Set: 8e349184-bc14-11e3-8d4c-0800272864ba:1-30, 8e3648e4-bc14-11e3-8d4c-0800272864ba:1-7 # Slave mysql> show slave status\G [...] Executed_Gtid_Set: 8e349184-bc14-11e3-8d4c-0800272864ba:1-29, 8e3648e4-bc14-11e3-8d4c-0800272864ba:1-9 # Now, let's compare the 2 sets mysql> > select gtid_subset('8e349184-bc14-11e3-8d4c-0800272864ba:1-29, 8e3648e4-bc14-11e3-8d4c-0800272864ba:1-9','8e349184-bc14-11e3-8d4c-0800272864ba:1-30, 8e3648e4-bc14-11e3-8d4c-0800272864ba:1-7') as slave_is_subset; +-----------------+ | slave_is_subset | +-----------------+ | 0 | +-----------------+

Hum, it looks like the slave has executed more transactions than the master, this indicates that the slave has executed at least 1 errant transaction. Could we know the GTID of these transactions? Sure, let’s use GTID_SUBTRACT():

select gtid_subtract('8e349184-bc14-11e3-8d4c-0800272864ba:1-29, 8e3648e4-bc14-11e3-8d4c-0800272864ba:1-9','8e349184-bc14-11e3-8d4c-0800272864ba:1-30, 8e3648e4-bc14-11e3-8d4c-0800272864ba:1-7') as errant_transactions; +------------------------------------------+ | errant_transactions | +------------------------------------------+ | 8e3648e4-bc14-11e3-8d4c-0800272864ba:8-9 | +------------------------------------------+

This means that the slave has 2 errant transactions.

Now, how can we check errant transactions if the master is not running (like master has crashed, and we want to fail over to one of the slaves)? In this case, we will have to follow these steps:

  • Check all slaves to see if they have executed transactions that are not found on any other slave: this is the list of potential errant transactions.
  • Discard all transactions originating from the master: now you have the list of errant transactions of each slave

Some of you may wonder how you can know which transactions come from the master as it is not available: SHOW SLAVE STATUS gives you the master’s UUID which is used in the GTIDs of all transactions coming from the master.

How to get rid of them?

This is pretty easy, but it can be tedious if you have many slaves: just inject an empty transaction on all the other servers with the GTID of the errant transaction.

For instance, if you have 3 servers, A (the master), B (slave with an errant transaction: XXX:3), and C (slave with 2 errant transactions: YYY:18-19), you will have to inject the following empty transactions in pseudo-code:

# A - Inject empty trx(XXX:3) - Inject empty trx(YYY:18) - Inject empty trx(YYY:19) # B - Inject empty trx(YYY:18) - Inject empty trx(YYY:19) # C - Inject empty trx(XXX:3)

Conclusion

If you want to switch to GTID-based replication, make sure to check errant transactions before any planned or unplanned replication topology change. And be specifically careful if you use a tool that reconfigures replication for you: at the time of writing, only mysqlrpladmin and mysqlfailover from MySQL Utilities can warn you if you are trying to perform an unsafe topology change.

The post Errant transactions: Major hurdle for GTID-based failover in MySQL 5.6 appeared first on MySQL Performance Blog.

Introduction to the Percona MySQL Audit Log Plugin

May 16, 2014 - 6:00am

Percona has developed a MySQL Audit Log plugin that is now included in Percona Server since the recent 5.5 and 5.6 releases. This implementation is alternative to the MySQL Enterprise Audit Log Plugin: Percona re-implemented the Audit Plugin code as GPL as Oracle’s code was closed source. This post is a quick introduction to this plugin.

Installation
There are two ways to install the Percona MySQL Audit Plugin:

INSTALL PLUGIN audit_log SONAME 'audit_log.so';

or in my.cnf

[mysqld] plugin-load="audit_log=audit_log.so"

Verify installation

mysql> SHOW PLUGINS\G ... *************************** 38. row ***************************   Name: audit_log Status: ACTIVE   Type: AUDIT Library: audit_log.so License: GPL 38 rows in set (0.00 sec)

Configuration
Let’s see variables provided by the Percona MySQL Audit Plugin:

mysql> show global variables like 'audit%'; +--------------------------+--------------+ | Variable_name            | Value        | +--------------------------+--------------+ | audit_log_buffer_size    | 1048576      | | audit_log_file           | audit.log    | | audit_log_flush          | OFF          | | audit_log_format         | OLD          | | audit_log_policy         | ALL          | | audit_log_rotate_on_size | 0            | | audit_log_rotations      | 0            | | audit_log_strategy       | ASYNCHRONOUS | +--------------------------+--------------+ 7 rows in set (0.00 sec)

The Percona MySQL Audit Plugin can log using the memory buffer to deliver better performance. Messages will be written into memory buffer first and then flushed to file in background. A certain amount of events can be lost in case of server crash or power outage. Another option is to log directly to file without using memory buffer. There is also an option to fsync every event.

Set audit_log_strategy to control log flushing:

  • ASYNCHRONOUS log using memory buffer, do not drop events if buffer is full
  • PERFORMANCE log using memory buffer, drop events if buffer is full
  • SEMISYNCHRONOUS log directly to file, do not fsync every event
  • SYNCHRONOUS log directly to file, fsync every event

audit_log_buffer_size specifies the size of memory buffer, it makes sense only for ASYNCHRONOUS and PERFORMANCE strategy.

Variable audit_log_file specifies the file to log into. It’s value can be path relative to datadir or absolute path.

The Percona MySQL Audit Plugin can automatically rotate log file based on size. Set audit_log_rotate_size to enable this feature. File is rotated when log grew in size to specified amount of bytes. Set audit_log_rotations to limit the number of log files to keep.

It is possible to log only logins or only queries by setting audit_log_policy value.

Log file format
Lets see how audit records look like

OLD format (audit_log_format = OLD):

<AUDIT_RECORD  "NAME"="Connect"  "RECORD"="2_2014-04-21T12:34:32"  "TIMESTAMP"="2014-04-21T12:34:32 UTC"  "CONNECTION_ID"="1"  "STATUS"="0"  "USER"="root"  "PRIV_USER"="root"  "OS_LOGIN"=""  "PROXY_USER"=""  "HOST"="localhost"  "IP"=""  "DB"="" />

NEW format (audit_log_format = NEW):

<AUDIT_RECORD>  <NAME>Connect</NAME>  <RECORD>17481_2014-04-21T12:39:03</RECORD>  <TIMESTAMP>2014-04-21T12:39:05 UTC</TIMESTAMP>  <CONNECTION_ID>4</CONNECTION_ID>  <STATUS>0</STATUS>  <USER>root</USER>  <PRIV_USER>root</PRIV_USER>  <OS_LOGIN></OS_LOGIN>  <PROXY_USER></PROXY_USER>  <HOST>localhost</HOST>  <IP></IP>  <DB>test</DB> </AUDIT_RECORD>

The difference is that the audit record in the OLD format was written as a single element with attributes, while in the NEW format it is written as a single element with sub-elements.

A good idea of what each sub-element means can be found in Audit Plugin API documentation here: https://dev.mysql.com/doc/refman/5.6/en/writing-audit-plugins.html.

Performance
Lets compare performance of different audit_log_strategy modes. I used readonly sysbench on my laptop for it. Workload is CPU-bound with dataset fit in buffer pool and I set number of sysbench threads to the amount for which count of transactions per seconds is maximum.

I got TPS drop for PERFORMANCE and ASYNCHRONOUS strategies around 7%, 9% for SEMISYNCHRONOUS and 98% for SYNCHRONOUS which shows that syncing every logged statement to disk is not the best thing for performance.

 

Conclusion
Of course any software has bugs and this plugin has plenty of them. Please give it a try and provide us your feedback. Report any issues here: https://bugs.launchpad.net/percona-server.

The post Introduction to the Percona MySQL Audit Log Plugin appeared first on MySQL Performance Blog.

Benchmark: SimpleHTTPServer vs pyclustercheck (twisted implementation)

May 16, 2014 - 12:00am

Github user Arianlzt provided a python-twisted alternative version of pyclustercheck per discussion on issue 7.

Due to sporadic performance issues noted with the original implementation in SimpleHTTPserver, the benchmarks which I’ve included as part of the project on github use mutli-mechanize library,

  • cache time 1 sec
  • 2 x 100 thread pools
  • 60s ramp up time
  • 600s total duration
  • testing simulated node fail (always returns 503, rechecks mysql node on cache expiry)
  • AMD FX(tm)-8350 Eight-Core Processor
  • Intel 330 SSD
  • local loop back test (127.0.0.1)

The SimpleHTTPServer instance faired as follows:

Right away we can see around 500TPS throughput, however as can be seen in both response time graphs there are “outlying” transactions, something is causing the response time to spike dramatically  SimpleHTTPServer, how does the twisted alternative compare? (note the benchmarks are from the current HEAD with features re-added to avoid regression, caching and ipv6 support)

 

Ouch! We appear to have taken a performance hit, at least in terms of TPS -19% rough estimates however compare the response time graphs to find a much more consistent plot, we had outliers hitting near  70s for SimpleHTTP server, we’re always under 1s within twisted.

Great! So why isn’t this merged into the master branch as the main project and therfor bundled with Percona XtraDB Cluster (PXC)? The issue here is the required version of python-twisted; ipv6 support was introduced in issue 8 by user Nibler999 and to avoid regression I re-added support for ipv6 in this commit for twisted

ipv6 support for python-twisted is not in the version distributed to main server OS’s such as

  • EL6 python-twisted 8.x
  • Ubuntu 10.04 LTS python-twisted 11.x

What’s the issue here? Attempting to bind / listen to an ipv6 interface yields the following error: twisted.internet.error.CannotListenError: Couldn't listen on :::8000: [Errno -9] Address family for hostname not supported.

Due to this regression (breaking of ipv6 support) the twisted version can not at this time be merged into master, the twisted version however as can be seen from above is much more consistent and if you have the “cycles” to implement it (e.g. install twisted from pypy via pip / easy_install to get >= 12.x) and test it’s a promising alternative.

To illustrate this further the benchmark was made more gruling:

  • 5 x 100 thread pools
  • 60s ramp up
  • 600s total duration

First the twisted results, note the initial spike is due to a local python issue where it locked up creating a new thread in multi-mechanize:

Now the SimpleHTTPServer results:

Oh dear, as the load increases clearly we get some stability issues inside SimpleHTTP server…

Also worth noting is the timeouts

  • twisted: grep 'timed out' results.csv | wc -l == 0
  • SimpleHTTPServer: grep 'timed out' results.csv | wc -l == 470

 

… in the case of increased load the twisted model performs far more consistently under the same test conditions when compared against SimpleHTTPServer. I include the multi-mechanize scripts as part of the project on GitHub – as such you can recreate these tests yourself and gauge the performance to see if twisted or SimpleHTTP suits your needs.

The post Benchmark: SimpleHTTPServer vs pyclustercheck (twisted implementation) appeared first on MySQL Performance Blog.

High Availability with MySQL Fabric: Part I

May 15, 2014 - 6:00am

In our previous post, we introduced the MySQL Fabric utility and said we would dig deeper into it. This post is the first part of our test of MySQL Fabric’s High Availability (HA) functionality.

Today, we’ll review MySQL Fabric’s HA concepts, and then walk you through the setup of a 3-node cluster with one Primary and two Secondaries, doing a few basic tests with it. In a second post, we will spend more time generating failure scenarios and documenting how Fabric handles them. (MySQL Fabric is an extensible framework to manage large farms of MySQL servers, with support for high-availability and sharding.)

Before we begin, we recommend you read this post by Oracle’s Mats Kindahl, which, among other things, addresses the issues we raised on our first post. Mats leads the MySQL Fabric team.

Our lab

All our tests will be using our test environment with Vagrant (https://github.com/martinarrieta/vagrant-fabric)

If you want to play with MySQL Fabric, you can have these VMs running in your desktop following the instructions in the README file. If you don’t want full VMs, our colleague Jervin Real created a set of wrapper scripts that let you test MySQL Fabric using sandboxes.

Here is a basic representation of our environment.

Set up

To set up MyQSL Fabric without using our Vagrant environment, you can follow the official documentation, or check the ansible playbooks in our lab repo. If you follow the manual, the only caveat is that when creating the user, you should either disable binary logging for your session, or use a GRANT statement instead of CREATE USER. You can read here for more info on why this is the case.

A description of all the options in the configuration file can be found here. For HA tests, the one thing to mention is that, in our experience, the failure detector will only trigger an automatic failover if the value for failover_interval in the [failure_tracking] section is greater than 0. Otherwise, failures will be detected and written to the log, but no action will be taken.

MySQL configuration

In order to manage a mysqld instance with MySQL Fabric, the following options need to be set in the [mysqld] section of its my.cnf file:

log_bin gtid-mode=ON enforce-gtid-consistency log_slave_updates

Additionally, as in any replication setup, you must make sure that all servers have a distinct server_id.

When everything is in place, you can setup and start MySQL Fabric with the following commands:

[vagrant@store ~]$ mysqlfabric manage setup [vagrant@store ~]$ mysqlfabric manage start --daemon

The setup command creates the database schema used by MySQL Fabric to store information about managed servers, and the start one, well, starts the daemon. The –daemon option makes Fabric start as a daemon, logging to a file instead of to standard output. Depending on the port and file name you configured in fabric.cfg, this may need to be run as root.

While testing, you can make MySQL Fabric reset its state at any time (though it won’t change existing node configurations such as replication) by running:

[vagrant@store ~]$ mysqlfabric manage teardown [vagrant@store ~]$ mysqlfabric manage setup

If you’re using our Vagrant environment, you can run the reinit_cluster.sh script from your host OS (from the root of the vagrant-fabric repo) to do this for you, and also initialise the datadir of the three instances.

Creating a High Availability Cluster:

A High Availability Cluster is a set of servers using the standard Asynchronous MySQL Replication with GTID.

Creating a group

The first step is to create the group by running mysqlfabric with this syntax:

$ mysqlfabric group create <group_name>

In our example, to create the cluster “mycluster” you can run:

[vagrant@store ~]$ mysqlfabric group create mycluster Procedure : { uuid = 605b02fb-a6a1-4a00-8e24-619cad8ec4c7, finished = True, success = True, return = True, activities = }

Add the servers to the group

The second step is add the servers to the group. The syntax to add a server to a group is:

$ mysqlfabric group add <group_name> <host_name or IP>[:port]

The port number is optional and only required if distinct from 3306. It is important to mention that the clients that will use this cluster must be able to resolve this host or IP. This is because clients will connect directly both with MySQL Fabric’s XML-PRC server and with the managed mysqld servers. Let’s add the nodes to our group.

[vagrant@store ~]$ for i in 1 2 3; do mysqlfabric group add mycluster node$i; done Procedure : { uuid = 9d65c81c-e28a-437f-b5de-1d47e746a318, finished = True, success = True, return = True, activities = } Procedure : { uuid = 235a7c34-52a6-40ad-8e30-418dcee28f1e, finished = True, success = True, return = True, activities = } Procedure : { uuid = 4da3b1c3-87cc-461f-9705-28a59a2a4f67, finished = True, success = True, return = True, activities = }

Promote a node as a master

Now that we have all our nodes in the group, we have to promote one of them. You can promote one specific node or you can let MySQL Fabric to choose one for you.

The syntax to promote a specific node is:

$ mysqlfabric group promote <group_name> --slave_uuid='<node_uuid>'

or to let MySQL Fabric pick one:

$ mysqlfabric group promote <group_name>

Let’s do that:

[vagrant@store ~]$ mysqlfabric group promote mycluster Procedure : { uuid = c4afd2e7-3864-4b53-84e9-04a40f403ba9, finished = True, success = True, return = True, activities = }

You can then check the health of the group like this:

[vagrant@store ~]$ mysqlfabric group health mycluster Command : { success = True return = {'e245ec83-d889-11e3-86df-0800274fb806': {'status': 'SECONDARY', 'is_alive': True, 'threads': {}}, 'e826d4ab-d889-11e3-86df-0800274fb806': {'status': 'SECONDARY', 'is_alive': True, 'threads': {}}, 'edf2c45b-d889-11e3-86df-0800274fb806': {'status': 'PRIMARY', 'is_alive': True, 'threads': {}}} activities = }

One current limitation of the ‘health’ command is that it only identifies servers by their uuid. To get a list of the servers in a group, along with quick status summary, and their host names, use lookup_servers instead:

[vagrant@store ~]$ mysqlfabric group lookup_servers mycluster Command : { success = True return = [{'status': 'SECONDARY', 'server_uuid': 'e245ec83-d889-11e3-86df-0800274fb806', 'mode': 'READ_ONLY', 'weight': 1.0, 'address': 'node1'}, {'status': 'SECONDARY', 'server_uuid': 'e826d4ab-d889-11e3-86df-0800274fb806', 'mode': 'READ_ONLY', 'weight': 1.0, 'address': 'node2'}, {'status': 'PRIMARY', 'server_uuid': 'edf2c45b-d889-11e3-86df-0800274fb806', 'mode': 'READ_WRITE', 'weight': 1.0, 'address': 'node3'}] activities = }

We sent a merge request to use a Json string instead of the “print” of the object in the “return” field from the XML-RPC in order to be able to use that information to display the results in a friendly way. In the same merge, we have added the address of the servers in the health command too.

Failure detection

Now we have the three lab machines set up in a replication topology of one master (the PRIMARY server) and two slaves (the SECONDARY ones). To make MySQL Fabric start monitoring the group for problems, you need to activate it:

[vagrant@store ~]$ mysqlfabric group activate mycluster Procedure : { uuid = 230835fc-6ec4-4b35-b0a9-97944c18e21f, finished = True, success = True, return = True, activities = }

Now MySQL Fabric will monitor the group’s servers, and depending on the configuration (remember the failover_interval we mentioned before) it may trigger an automatic failover. But let’s start testing a simpler case, by stopping mysql on one of the secondary nodes:

[vagrant@node2 ~]$ sudo service mysqld stop Stopping mysqld: [ OK ]

And checking how MySQL Fabric report’s the group’s health after this:

[vagrant@store ~]$ mysqlfabric group health mycluster Command : { success = True return = {'e245ec83-d889-11e3-86df-0800274fb806': {'status': 'SECONDARY', 'is_alive': True, 'threads': {}}, 'e826d4ab-d889-11e3-86df-0800274fb806': {'status': 'FAULTY', 'is_alive': False, 'threads': {}}, 'edf2c45b-d889-11e3-86df-0800274fb806': {'status': 'PRIMARY', 'is_alive': True, 'threads': {}}} activities = }

We can see that MySQL Fabric successfully marks the server as faulty. In our next post we’ll show an example of this by using one of the supported connectors to handle failures in a group, but for now, let’s keep on the DBA/sysadmin side of things, and try to bring the server back online:

[vagrant@node2 ~]$ sudo service mysqld start Starting mysqld: [ OK ] [vagrant@store ~]$ mysqlfabric group health mycluster Command : { success = True return = {'e245ec83-d889-11e3-86df-0800274fb806': {'status': 'SECONDARY', 'is_alive': True, 'threads': {}}, 'e826d4ab-d889-11e3-86df-0800274fb806': {'status': 'FAULTY', 'is_alive': True, 'threads': {}}, 'edf2c45b-d889-11e3-86df-0800274fb806': {'status': 'PRIMARY', 'is_alive': True, 'threads': {}}} activities = }

So the server is back online, but Fabric still considers it faulty. To add the server back into rotation, we need to look at the server commands:

[vagrant@store ~]$ mysqlfabric help server Commands available in group 'server' are: server set_weight uuid weight [--synchronous] server lookup_uuid address server set_mode uuid mode [--synchronous] server set_status uuid status [--update_only] [--synchronous]

The specific command we need is set_status, and in order to add the server back to the group, we need to change it’s status twice: first to SPARE and then back to SECONDARY. You can see what happens if we try to set it to SECONDARY directly:

[vagrant@store ~]$ mysqlfabric server set_status e826d4ab-d889-11e3-86df-0800274fb806 SECONDARY Procedure : { uuid = 9a6f2273-d206-4fa8-80fb-6bce1e5262c8, finished = True, success = False, return = ServerError: Cannot change server's (e826d4ab-d889-11e3-86df-0800274fb806) status from (FAULTY) to (SECONDARY)., activities = }

So let’s try it the right way:

[vagrant@store ~]$ mysqlfabric server set_status e826d4ab-d889-11e3-86df-0800274fb806 SPARE Procedure : { uuid = c3a1c244-ea8f-4270-93ed-3f9dfbe879ea, finished = True, success = True, return = True, activities = } [vagrant@store ~]$ mysqlfabric server set_status e826d4ab-d889-11e3-86df-0800274fb806 SECONDARY Procedure : { uuid = 556f59ec-5556-4225-93c9-b9b29b577061, finished = True, success = True, return = True, activities = }

And check the group’s health again:

[vagrant@store ~]$ mysqlfabric group health mycluster Command : { success = True return = {'e245ec83-d889-11e3-86df-0800274fb806': {'status': 'SECONDARY', 'is_alive': True, 'threads': {}}, 'e826d4ab-d889-11e3-86df-0800274fb806': {'status': 'SECONDARY', 'is_alive': True, 'threads': {}}, 'edf2c45b-d889-11e3-86df-0800274fb806': {'status': 'PRIMARY', 'is_alive': True, 'threads': {}}} activities = }

In our next post, when we discuss how to use the Fabric aware connectors, we’ll also test other failure scenarios like hard VM shutdown and network errors, but for now, let’s try the same thing but on the PRIMARY node instead:

[vagrant@node3 ~]$ sudo service mysqld stop Stopping mysqld: [ OK ]

And let’s check the servers again:

[vagrant@store ~]$ mysqlfabric group lookup_servers mycluster Command : { success = True return = [{'status': 'SECONDARY', 'server_uuid': 'e245ec83-d889-11e3-86df-0800274fb806', 'mode': 'READ_ONLY', 'weight': 1.0, 'address': 'node1'}, {'status': 'PRIMARY', 'server_uuid': 'e826d4ab-d889-11e3-86df-0800274fb806', 'mode': 'READ_WRITE', 'weight': 1.0, 'address': 'node2'}, {'status': 'FAULTY', 'server_uuid': 'edf2c45b-d889-11e3-86df-0800274fb806', 'mode': 'READ_WRITE', 'weight': 1.0, 'address': 'node3'}] activities = }

We can see that MySQL Fabric successfully marked node3 as FAULTY, and promoted node2 to PRIMARY to resolve this. Once we start mysqld again on node3, we can add it back as SECONDARY using the same process of setting it’s status to SPARE first, as we did for node2 above.

Remember that unless failover_interval is greater than 0, MySQL Fabric will detect problems in an active group, but it won’t take any automatic action. We think it’s a good thing that the value for this variable in the documentation is 0, so that automatic failover is not enabled by default (if people follow the manual, of course), as even in mature HA solutions like Pacemaker, automatic failover is something that’s tricky to get right. But even without this, we believe the main benefit of using MySQL Fabric for promotion is that it takes care of reconfiguring replication for you, which should reduce the risk for error in this process, specially once the project becomes GA.

What’s next

In this post we’ve presented a basic replication setup managed by MySQL Fabric and reviewed a couple of failure scenarios, but many questions are left unanswered, among them:

  • What happens to clients connected with a Fabric aware driver when there is a status change in the cluster?
  • What happens when the XML-RPC server goes down?
  • How can we improve its availability?

We’ll try to answer these and other questions in our next post. If you have some questions of your own, please leave them in the comments section and we’ll address them in the next or other posts, depending on the topic.

The post High Availability with MySQL Fabric: Part I appeared first on MySQL Performance Blog.

Why ALTER TABLE runs faster on Percona Server 5.5 vs. MySQL 5.5

May 15, 2014 - 3:00am

Some of us Perconians are at OpenStack summit this week in Atlanta. Matt Griffin, our director of product management, tweeted about the turbo-hipster CI talk about their experience of ALTER TABLEs running faster on Percona Server. Oracle’s Morgan Tocker then tweeted in response, asking why this was the case. I decided that the simplest way to answer that was here in this post.

The reason for this is the expand_fast_index_creation feature of Percona Server. I did a quick schema change on MySQL 5.5 and Percona Server 5.5 to demonstrate this (in the talk, the speaker mentioned that these versions were used).

The schema modifications in the talk could fall in 2 categories, the ones that could use fast index creation and the ones that could not.

I did the following tests on my laptop, on a sysbench tale with 300k records.

Vanilla MySQL 5.5:

mysql> alter table sbtest1 add index idx_c(c); Query OK, 0 rows affected (4.37 sec)

Percona Server 5.5:

mysql> alter table sbtest1 add index idx_c(c); Query OK, 0 rows affected (3.90 sec)

We know that this used fast index creation from the 0 rows affected. In this case, there is nor substantial difference between the 2 servers, also probably my laptop with CPU frewquency scaling doesn’t have the most consistent performance in the world.

For the second schema change, I added a column which copies the table.

Vanilla MySQL 5.5:

mysql> alter table sbtest1 add column d int default 0; Query OK, 300000 rows affected (37.05 sec) Records: 300000 Duplicates: 0 Warnings: 0

Percona Server 5.5:

mysql> alter table sbtest1 add column d int default 0; Query OK, 300000 rows affected (9.51 sec) Records: 300000 Duplicates: 0 Warnings: 0

The reason for this speed difference is that in case of Percona Server, for the table copy, the table is created only with a primary key, and the secondary indexes are built at the end of the process (rather than on the fly). For more details, check Alexey’s blog post on this topic.

This can be tuned further, by tuning innodb_merge_sort_block_size (in Percona Server 5.6, this is replaced by innodb_sort_buffer_size).

mysql> select @@innodb_merge_sort_block_size/1024/1024; +------------------------------------------+ | @@innodb_merge_sort_block_size/1024/1024 | +------------------------------------------+ | 1.00000000 | +------------------------------------------+ 1 row in set (0.00 sec) mysql> set innodb_merge_sort_block_size=8*1024*1024; Query OK, 0 rows affected (0.00 sec) mysql> alter table sbtest1 add column d int default 0; Query OK, 300000 rows affected (8.61 sec) Records: 300000 Duplicates: 0 Warnings: 0

So, in order to be accurate, schema changes are faster in Percona Server if they are table copies and if the tables have secondary indexes.

The post Why ALTER TABLE runs faster on Percona Server 5.5 vs. MySQL 5.5 appeared first on MySQL Performance Blog.

Tips on benchmarking Go + MySQL

May 14, 2014 - 9:00am

We just released, as an open source release, our new percona-agent (https://github.com/percona/percona-agent), the agent to work with Percona Cloud Tools. This agent is written in Go.

I will give a webinar titled “Monitoring All MySQL Metrics with Percona Cloud Tools” on June 25 that will cover the new features in percona-agent and Percona Cloud Tools, where I will also explain how it works. You are welcome to register now and join me.

There will be more posts about percona-agent, but in the meantime I want to dedicate this one to Go, Go with MySQL and some performance topics.

I have had an interest in the Go programming language for a long time, but in initial versions I did not quite like the performance of the gorountine scheduler. See my report from more than two years ago on runtime: reduce scheduling contention for large $GOMAXPROCS.

Supposedly this performance issue was fixed in Go 1.1, so this is a good time to revisit my benchmark experiment.

A simple run of prime or fibonachi numbers calculation in N threas is quite boring, so I am going to run queries against Percona Server. Of course it adds some complication as there are more moving parts (i.e. go scheduler, go sql driver, MySQL by itself), but it just makes the experiment more interesting.

Source code of my benchmark: Go-pk-bench:
This is probably not the best example of how to code in Go, but that was not the point of this exercise. This post is really about some tips to take into account when writing an application in Go using a MySQL (Percona Server) database.

So, first, we will need a MySQL driver for Go. The one I used two years ago (https://github.com/Philio/GoMySQL) is quite outdated. It seems the most popular choice today is Go-MySQL-Driver, and this is the one we use for internal development. This driver is based on the standard Go “database/sql” package. This package kind of provides a standard Go-way to deal with SQL-like databases. “database/sql” seems to work out OK, with some questionable design decisions as for my taste. So using “database/sql” and Go-MySQL-Driver you will need to deal with some quirks like almost unmanageable connection pool.

The first thing you should take into account it is a proper setting of
runtime.GOMAXPROCS().

If you do not do that, Go scheduler will use the default, which is 1. That binary will use one and only 1 CPU (so much for a modern concurrent language).

The command runtime.GOMAXPROCS(runtime.NumCPU())
will prescribe to use all available CPUs. Always remember to use this if you care about multi-threaded performance.

The next problem I faced in the benchmark is that when I ran queries in a loop, i.e. to repeat as much possible…

rows, err := db.Query("select k from sbtest"+strconv.Itoa(tab+1)+" where id = "+strconv.Itoa(i))

… very soon we ran out of TCP ports. Apparently “database/sql” and Go-MySQL-Driver and its smart connection pool creates a NEW CONNECTION for each query. I can explain why this happens, but using the following statement:

'db.SetMaxIdleConns(10000)'

helps (I hope somebody with “database/sql” knowledge will explain what it is doing).

So after these adjustments we now can run the benchmark, which by query you see is quite simple – run primary key lookups against Percona Server which we know scales perfectly in this scenario (I used sysbench to create 64 tables 1mln rows each, all this fits into memory). I am going to run this benchmark with 1, 2, 4, 8, 16, 24, 32, 48, 64 user threads.

Below you can see graphs for MySQL Throughput and CPU Usage (both graph are built using new metrics graphing in Percona Cloud Tools)

MySQL Throughput (user threads are increasing from 1 to 64)

CPU Usage (user threads are increasing from 1 to 64)

I would say the result scales quite nicely, at least it is really much better than it was two years ago. It is interesting to compare with something, so there is a graph from an identical run, but now I will use sysbench + lua for main workload driver.

MySQL Throughput (sysbench, user threads are increasing from 1 to 64)

CPU Usage (sysbench, user threads are increasing from 1 to 64)

From the graphs (this is what I like them for), we can clearly see increases in User CPU utilization (and actually we are able to use CPUs on 100% in user+system usage) and it clearly corresponds to increased throughput.

And if you are a fan of raw numbers:

MySQL Throughput, q/s (more is better) Threads | Go-MySQL | sysbench 1 | 13,189 | 16,765 2 | 26,837 | 33,534 4 | 52,629 | 65,943 8 | 95,553 | 116,953 16 | 146,979 | 182,781 24 | 169,739 | 231,895 32 | 181,334 | 245,939 48 | 198,238 | 250,497 64 | 207,732 | 251,972

(one with a knowledge of Universal Scalability Law can draw a prediction till 1000 threads, I leave it as a homework)

So, in conclusion, I can say that Go+MySQL is able to show decent results, but it is still not as effective as plan raw C (sysbench), as it seems it spends some extra CPU time in system calls.

If you want to try these new graphs in Percona Cloud Tools and see how it works with your system – join the free beta!

The post Tips on benchmarking Go + MySQL appeared first on MySQL Performance Blog.

max_allowed_packet and binary log corruption in MySQL

May 14, 2014 - 1:00am

The combination of max_allowed_packet variable and replication in MySQL is a common source of headaches. In a nutshell, max_allowed_packet is the maximum size of a MySQL network protocol packet that the server can create or read. It has a default value of 1MB (<= 5.6.5) or 4MB (>= 5.6.6) and a maximum size of 1GB. This adds some constraints in our replication environment:

  • The master server shouldn’t write events to the binary log larger than max_allowed_packet
  • All the slaves in the replication chain should have the same max_allowed_packet as the master server

Sometimes, even following those two basic rules we can have problems.

For example, there are situations (also called bugs) where the master writes more data than the max_allowed_packet limit causing the slaves to stop working. In order to fix this Oracle created a new variable called slave_max_allowed_packet. This new configuration variable available from 5.1.64, 5.5.26 and 5.6.6 overrides the max_allowed_packet value for slave threads. Therefore, regardless of the max_allowed_packet value the slaves’ threads will have 1GB limit, the default value of slave_max_allowed_packet. Nice trick that works as expected.

Sometimes even with that workaround we can get the max_allowed_packet error in the slave servers. That means that there is a packet larger than 1GB, something that shouldn’t happen in a normal situation. Why? Usually it is caused by a binary log corruption. Let’s see the following example:

Slave stops working with the following message:

Last_IO_Error: Got fatal error 1236 from master when reading data from binary log: 'log event entry exceeded max_allowed_packet; Increase max_allowed_packet on master'

The important part is “got fatal error 1236 from master”. The master cannot read the event it wrote to the binary log seconds ago. To check the problem we can:

  • Use mysqlbinlog to read the binary log from the position it failed with –start-position.

This is an example taken from our Percona Forums:

#121003 5:22:26 server id 1 end_log_pos 398528 # Unknown event # at 398528 #960218 6:48:44 server id 1813111337 end_log_pos 1835008 # Unknown event ERROR: Error in Log_event::read_log_event(): 'Event too big', data_len: 1953066613, event_type: 8 DELIMITER ; # End of log file

Check the size of the event, 1953066613 bytes. Or the “Unknown event” messages. Something is clearly wrong there. Another usual thing to check is the server id that sometimes doesn’t correspond with the real value. In this example the person who posted the binary log event confirmed that the server id was wrong.

  • Check master’s error log.

[ERROR] Error in Log_event::read_log_event(): 'Event too big', data_len: 1953066613, event_type: 8

Again, the event is bigger than expected. There is no way the master and slave can read/write it, so the solution is to skip that event in the slave and rotate the logs on the master. Then, use pt-table-checksum to check data consistency.

MySQL 5.6 includes replication checksums to avoid problems with log corruptions. You can read more about it in Stephan’s blog post.

Conclusion

Errors on slave servers about max_allowed_packet can be caused by very different reasons. Although binary log corruption is not a common one, it is something worth checking when you have run out of ideas.

The post max_allowed_packet and binary log corruption in MySQL appeared first on MySQL Performance Blog.

Using Percona Server 5.6 with the Docker open-source engine

May 13, 2014 - 12:00am

There are a couple of posts about setting up Percona XtraDB Cluster on Vagrant and Percona Server on MySQL Sandbox – those are two of the top tools used by the Percona Support team for testing and bug processing among other things.

In this post, however, I will show you how to use Docker with Percona Server on Ubuntu 12.04.

As per Docker’s official site:

Docker is an open-source engine that automates the deployment of any application as a lightweight, portable, self-sufficient container that will run virtually anywhere.

Docker containers can encapsulate any payload, and will run consistently on and between virtually any server. The same container that a developer builds and tests on a laptop will run at scale, in production*, on VMs, bare-metal servers, OpenStack clusters, public instances, or combinations of the above.

To install Docker on Ubuntu 12.04 you need to follow instructions from Docker’s official documentation:
http://docs.docker.io/installation/ubuntulinux/#ubuntu-precise-1204-lts-64-bit

After installing Docker, you may either download docker images via ‘docker pull’ and store docker images on your server so you can spin a new docker container in an instance or you may choose to do a ‘docker run’ on the terminal and implicitly download/store the specific docker image from index.docker.io and run the image afterward.

root@Perconallc-Support / # docker images | grep centos centos centos6 0b443ba03958 2 weeks ago 297.6 MB centos latest 0b443ba03958 2 weeks ago 297.6 MB centos 6.4 539c0211cd76 13 months ago 300.6 MB

Let us create a CentOS docker container by running the following command:

root@Perconallc-Support / # docker run -i -t centos:latest bash bash-4.1# cat /etc/redhat-release CentOS release 6.5 (Final)

As you may have noticed, we have just created a new interactive (-i) CentOS 6.5 docker container and ran bash in a single line of command. Detaching from the container is as easy as typing CTRL+p – CTRL+q, you’ll get to your terminal if you typed the right keys.

Verify the active containers:

root@Perconallc-Support / # docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 202765d754b7 centos:centos6 bash 11 minutes ago Up 11 minutes elegant_rosalind

To list all existing containers active or not use the following command:

root@Perconallc-Support / # docker ps -a CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 202765d754b7 centos:centos6 bash 12 minutes ago Up 12 minutes elegant_rosalind aae47d193a22 centos:6.4 bash 2 hours ago Exited (1) 2 hours ago boring_bardeen

To attach to the active docker container:

root@Perconallc-Support / # docker attach 202765d754b7 bash-4.1#

*Tip: Hit enter twice to get to the container’s bash prompt.*

Install Percona Server 5.6

Now that you have a working docker container you will then have to install the needed packages and repository.

bash-4.1# rpm -Uhv http://www.percona.com/downloads/percona-release/percona-release-0.0-1.x86_64.rpm Retrieving http://www.percona.com/downloads/percona-release/percona-release-0.0-1.x86_64.rpm Preparing... ########################################### [100%] 1:percona-release ########################################### [100%] bash-4.1# yum install Percona-Server-server-56 Percona-Server-client-56 Percona-Server-shared-56 Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile * base: ftp.hosteurope.de * extras: ftp.plusline.de * updates: ftp.plusline.de Setting up Install Process Resolving Dependencies --> Running transaction check ---> Package Percona-Server-client-56.x86_64 0:5.6.17-rel65.0.el6 will be installed --> Processing Dependency: /usr/bin/perl for package: Percona-Server-client-56-5.6.17-rel65.0.el6.x86_64 ---> Package Percona-Server-server-56.x86_64 0:5.6.17-rel65.0.el6 will be installed --> Processing Dependency: libaio.so.1(LIBAIO_0.1)(64bit) for package: Percona-Server-server-56-5.6.17-rel65.0.el6.x86_64 --> Processing Dependency: libaio.so.1(LIBAIO_0.4)(64bit) for package: Percona-Server-server-56-5.6.17-rel65.0.el6.x86_64 --> Processing Dependency: libaio.so.1()(64bit) for package: Percona-Server-server-56-5.6.17-rel65.0.el6.x86_64 ---> Package Percona-Server-shared-56.x86_64 0:5.6.17-rel65.0.el6 will be installed --> Running transaction check ---> Package libaio.x86_64 0:0.3.107-10.el6 will be installed ---> Package perl.x86_64 4:5.10.1-136.el6 will be installed --> Processing Dependency: perl-libs = 4:5.10.1-136.el6 for package: 4:perl-5.10.1-136.el6.x86_64 --> Processing Dependency: perl-libs for package: 4:perl-5.10.1-136.el6.x86_64 --> Processing Dependency: perl(version) for package: 4:perl-5.10.1-136.el6.x86_64 --> Processing Dependency: perl(Pod::Simple) for package: 4:perl-5.10.1-136.el6.x86_64 --> Processing Dependency: perl(Module::Pluggable) for package: 4:perl-5.10.1-136.el6.x86_64 --> Processing Dependency: libperl.so()(64bit) for package: 4:perl-5.10.1-136.el6.x86_64 --> Running transaction check ---> Package perl-Module-Pluggable.x86_64 1:3.90-136.el6 will be installed ---> Package perl-Pod-Simple.x86_64 1:3.13-136.el6 will be installed --> Processing Dependency: perl(Pod::Escapes) >= 1.04 for package: 1:perl-Pod-Simple-3.13-136.el6.x86_64 ---> Package perl-libs.x86_64 4:5.10.1-136.el6 will be installed ---> Package perl-version.x86_64 3:0.77-136.el6 will be installed --> Running transaction check ---> Package perl-Pod-Escapes.x86_64 1:1.04-136.el6 will be installed --> Finished Dependency Resolution Dependencies Resolved ======================================================================================================================================================================== Package Arch Version Repository Size ======================================================================================================================================================================== Installing: Percona-Server-client-56 x86_64 5.6.17-rel65.0.el6 percona 6.8 M Percona-Server-server-56 x86_64 5.6.17-rel65.0.el6 percona 19 M Percona-Server-shared-56 x86_64 5.6.17-rel65.0.el6 percona 714 k Installing for dependencies: libaio x86_64 0.3.107-10.el6 base 21 k perl x86_64 4:5.10.1-136.el6 base 10 M perl-Module-Pluggable x86_64 1:3.90-136.el6 base 40 k perl-Pod-Escapes x86_64 1:1.04-136.el6 base 32 k perl-Pod-Simple x86_64 1:3.13-136.el6 base 212 k perl-libs x86_64 4:5.10.1-136.el6 base 578 k perl-version x86_64 3:0.77-136.el6 base 51 k Transaction Summary ======================================================================================================================================================================== Install 10 Package(s) Total download size: 38 M Installed size: 158 M Is this ok [y/N]: y Downloading Packages: (1/10): Percona-Server-client-56-5.6.17-rel65.0.el6.x86_64.rpm | 6.8 MB 00:02 (2/10): Percona-Server-server-56-5.6.17-rel65.0.el6.x86_64.rpm | 19 MB 00:00 (3/10): Percona-Server-shared-56-5.6.17-rel65.0.el6.x86_64.rpm | 714 kB 00:00 (4/10): libaio-0.3.107-10.el6.x86_64.rpm | 21 kB 00:00 (5/10): perl-5.10.1-136.el6.x86_64.rpm | 10 MB 00:00 (6/10): perl-Module-Pluggable-3.90-136.el6.x86_64.rpm | 40 kB 00:00 (7/10): perl-Pod-Escapes-1.04-136.el6.x86_64.rpm | 32 kB 00:00 (8/10): perl-Pod-Simple-3.13-136.el6.x86_64.rpm | 212 kB 00:00 (9/10): perl-libs-5.10.1-136.el6.x86_64.rpm | 578 kB 00:00 (10/10): perl-version-0.77-136.el6.x86_64.rpm | 51 kB 00:00 ------------------------------------------------------------------------------------------------------------------------------------------------------------------------ Total 7.4 MB/s | 38 MB 00:05 Running rpm_check_debug Running Transaction Test Transaction Test Succeeded Running Transaction Warning: RPMDB altered outside of yum. ** Found 2 pre-existing rpmdb problem(s), 'yum check' output follows: udev-147-2.51.el6.x86_64 has missing requires of /sbin/service udev-147-2.51.el6.x86_64 has missing requires of MAKEDEV >= ('0', '3.11', None) Installing : Percona-Server-shared-56-5.6.17-rel65.0.el6.x86_64 1/10 Installing : 1:perl-Pod-Escapes-1.04-136.el6.x86_64 2/10 Installing : 1:perl-Module-Pluggable-3.90-136.el6.x86_64 3/10 Installing : 4:perl-libs-5.10.1-136.el6.x86_64 4/10 Installing : 3:perl-version-0.77-136.el6.x86_64 5/10 Installing : 1:perl-Pod-Simple-3.13-136.el6.x86_64 6/10 Installing : 4:perl-5.10.1-136.el6.x86_64 7/10 Installing : Percona-Server-client-56-5.6.17-rel65.0.el6.x86_64 8/10 Installing : libaio-0.3.107-10.el6.x86_64 9/10 Installing : Percona-Server-server-56-5.6.17-rel65.0.el6.x86_64 10/10 ... Installed: Percona-Server-client-56.x86_64 0:5.6.17-rel65.0.el6 Percona-Server-server-56.x86_64 0:5.6.17-rel65.0.el6 Percona-Server-shared-56.x86_64 0:5.6.17-rel65.0.el6 Dependency Installed: libaio.x86_64 0:0.3.107-10.el6 perl.x86_64 4:5.10.1-136.el6 perl-Module-Pluggable.x86_64 1:3.90-136.el6 perl-Pod-Escapes.x86_64 1:1.04-136.el6 perl-Pod-Simple.x86_64 1:3.13-136.el6 perl-libs.x86_64 4:5.10.1-136.el6 perl-version.x86_64 3:0.77-136.el6 Complete! bash-4.1# /etc/init.d/mysql start Starting MySQL (Percona Server). SUCCESS! bash-4.1# mysql Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 1 Server version: 5.6.17-65.0-56 Percona Server (GPL), Release 65.0, Revision 587 Copyright (c) 2009-2014 Percona LLC and/or its affiliates Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved. Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. mysql>

There you have it, a freshly installed Percona Server 5.6.17 on CentOS 6.5 Linux container. Yay!

You can now create a new MySQL user to access the server outside the container:

mysql> grant all privileges on *.* to 'test_user'@'%' identified by 'test_pass'; Query OK, 0 rows affected (0.00 sec) mysql> flush privileges; Query OK, 0 rows affected (0.00 sec) root@Perconallc-Support / # mysql -h 172.17.0.2 -utest_user -p Enter password: Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 4 Server version: 5.6.17-65.0-56 Percona Server (GPL), Release 65.0, Revision 587 Copyright (c) 2009-2014 Percona LLC and/or its affiliates Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved. Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. mysql>

We’re basically following installation instructions for Percona Server from the documentation.

Just the same way as you would do on any server, you can install other equally important Percona software on the same container to complete your docker environment.

As an added bonus, you can contribute to the Docker Community by commiting your container and pushing it to the docker registry.

Summary

I’ve shown you how easy it is to spin a docker container and install Percona Server 5.6 in it. This is by far one of the fastest ways to create test/staging environments to simulate production servers. For further reading you may want to read Docker’s official documentation here.

I hope that this has piqued your interest to try it out yourself. And if that happens we would love to know how Percona Server and other Percona software perform on your docker environment. Cheers!

The post Using Percona Server 5.6 with the Docker open-source engine appeared first on MySQL Performance Blog.

Practical MySQL performance optimization: May 14 Webinar

May 12, 2014 - 3:00am

Achieving the best possible MySQL Performance doesn’t have to be complicated. It’s all about knowing which tools are designed for the task at hand – along with some basic (yet often overlooked) best practices.

Join me Wednesday, May 14 at 10 a.m. Pacific for a free webinar titled, “Practical MySQL performance optimization.” I’ll be sharing the main areas for improving MySQL performance – along with what to specifically focus on in each. These will include:

  • Hardware
  • MySQL Configuration
  • Schema and Queries
  • Application Architecture

And as I mentioned earlier, I’ll also show you the best tools for the job and how to use them efficiently. This will help you optimize your time by focusing on the queries that are most important for your application.

At the end of this webinar, you will know how to optimize MySQL performance in the most practical way possible. The webinar is free but I recommend registering now to reserve your spot. I hope to see you on May 14!

The post Practical MySQL performance optimization: May 14 Webinar appeared first on MySQL Performance Blog.

GTIDs in MySQL 5.6: New replication protocol; new ways to break replication

May 9, 2014 - 12:00am

One of the MySQL 5.6 features many people are interested in is Global Transactions IDs (GTIDs). This is for a good reason: Reconnecting a slave to a new master has always been a challenge while it is so trivial when GTIDs are enabled. However, using GTIDs is not only about replacing good old binlog file/position with unique identifiers, it is also using a new replication protocol. And if you are not aware of it, it can bite.

Replication protocols: old vs new

The old protocol is pretty straightforward: the slave connects to a given binary log file at a specific offset, and the master sends all the transactions from there.

The new protocol is slightly different: the slave first sends the range of GTIDs it has executed, and then the master sends every missing transaction. It also guarantees that a transaction with a given GTID can only be executed once on a specific slave.

In practice, does it change anything? Well, it may change a lot of things. Imagine the following situation: you want to start replicating from trx 4, but trx 2 is missing on the slave for some reason.

With the old replication protocol, trx 2 will never be executed while with the new replication protocol, it WILL be executed automatically.

Here are 2 common situations where you can see the new replication protocol in action.

Skipping transactions

It is well known that the good old SET GLOBAL sql_slave_skip_counter = N is no longer supported when you want to skip a transaction and GTIDs are enabled. Instead, to skip the transaction with GTID XXX:N, you have to inject an empty transaction:

mysql> SET gtid_next = 'XXX:N'; mysql> BEGIN; COMMIT; mysql> SET gtid_next = 'AUTOMATIC';

Why can’t we use sql_slave_skip_counter? Because of the new replication protocol!

Imagine that we have 3 servers like the picture below:

Let’s assume that sql_slave_skip_counter is allowed and has been used on S2 to skip trx 2. What happens if you make S2 a slave of S1?

Both servers will exchange the range of executed GTIDs, and S1 will realize that it has to send trx 2 to S2. Two options then:

  • If trx 2 is still in the binary logs of S1, it will be sent to S2, and the transaction is no longer skipped.
  • If trx 2 no longer exists in the binary logs of S1, you will get a replication error.

This is clearly not safe, that’s why sql_slave_skip_counter is not allowed with GTIDs. The only safe option to skip a transaction is to execute a fake transaction instead of the real one.

Errant transactions

If you execute a transaction locally on a slave (called errant transaction in the MySQL documentation), what will happen if you promote this slave to be the new master?

With the old replication protocol, basically nothing (to be accurate, data will be inconsistent between the new master and its slaves, but that can probably be fixed later).

With the new protocol, the errant transaction will be identified as missing everywhere and will be automatically executed on failover, which has the potential to break replication.

Let’s say you have a master (M), and 2 slaves (S1 and S2). Here are 2 simple scenarios where reconnecting slaves to the new master will fail (with different replication errors):

# Scenario 1

# S1 mysql> CREATE DATABASE mydb; # M mysql> CREATE DATABASE IF NOT EXISTS mydb; # Thanks to 'IF NOT EXITS', replication doesn't break on S1. Now move S2 to S1: # S2 mysql> STOP SLAVE; CHANGE MASTER TO MASTER_HOST='S1'; START SLAVE; # This creates a conflict with existing data! mysql> SHOW SLAVE STATUS\G [...] Last_SQL_Errno: 1007 Last_SQL_Error: Error 'Can't create database 'mydb'; database exists' on query. Default database: 'mydb'. Query: 'CREATE DATABASE mydb' [...]

# Scenario 2

# S1 mysql> CREATE DATABASE mydb; # Now, we'll remove this transaction from the binary logs # S1 mysql> FLUSH LOGS; mysql> PURGE BINARY LOGS TO 'mysql-bin.000008'; # M mysql> CREATE DATABASE IF NOT EXISTS mydb; # S2 mysql> STOP SLAVE; CHANGE MASTER TO MASTER_HOST='S1'; START SLAVE; # The missing transaction is no longer available in the master's binary logs! mysql> SHOW SLAVE STATUS\G [...] Last_IO_Errno: 1236 Last_IO_Error: Got fatal error 1236 from master when reading data from binary log: 'The slave is connecting using CHANGE MASTER TO MASTER_AUTO_POSITION = 1, but the master has purged binary logs containing GTIDs that the slave requires.' [...]

As you can understand, errant transactions should be avoided with GTID-based replication. If you need to run a local transaction, your best option is to disable binary logging for that specific statement:

mysql> SET SQL_LOG_BIN = 0; mysql> # Run local transaction

Conclusion

GTIDs are a great step forward in the way we are able to reconnect replicas to other servers. But they also come with new operational challenges. If you plan to use GTIDs, make sure you correctly understand the new replication protocol, otherwise you may end up breaking replication in new and unexpected ways.

I’ll do more exploration about errant transactions in a future post.

The post GTIDs in MySQL 5.6: New replication protocol; new ways to break replication appeared first on MySQL Performance Blog.

Percona XtraDB Cluster 5.5.37-25.10 is now available

May 8, 2014 - 10:40am

Percona is glad to announce the release of Percona XtraDB Cluster 5.5.37-25.10 on May 8, 2014. Binaries are available from the downloads area or from our software repositories.

Based on Percona Server 5.5.37-35.0 including all the bug fixes in it, Galera Replicator 2.10 (including fixes in 2.9 and 2.10 milestones) and on wsrep API 25.10 (including fixes in 25.10), Percona XtraDB Cluster 5.5.37-25.10 is now the current stable release. All of Percona‘s software is open-source and free.

New Features:

  • Percona XtraDB Cluster now supports stream compression/decompression with new xtrabackup-sst compressor/decompressor options.
  • Garbd init script and configuration files have been packaged for CentOS and Debian, in addition, in Debian garbd is packaged separately in percona-xtradb-cluster-garbd-2.x package.
  • New meta packages are now available in order to make the Percona XtraDB Cluster installation easier.
  • Debian/Ubuntu debug packages are now available for Galera and garbd.
  • New SST options have been implemented: inno-backup-opts, inno-apply-opts, inno-move-opts which pass options to backup, apply and move stages of innobackupex.
  • Initial configurable timeout, of 100 seconds, to receive a first packet via SST has been implemented, so that if donor dies somewhere in between, joiner doesn’t hang. Timeout can be configured with the sst-initial-timeout variable.
  • The joiner would wait and not fall back to choosing other potential donor nodes (not listed in wsrep_sst_donor) by their state. This happened even when comma was added at the end. This fixes it for that particular case.
  • Support for Query Cache has been implemented.
  • Percona XtraDB Cluster packages are now available for Ubuntu 14.04.

Bugs Fixed:

  • To avoid disabling Parallel Apply in case of SAVEPOINT or ROLLBACK TO SAVEPOINT the wsrep_cert_deps_distance was set to 1.0 at all times. Bug fixed #1277703.
  • First connection would hang after changing the wsrep_cluster_address variable. Bug fixed #1022250.
  • When gmcast.listen_addr variable was set manually it did not allow node’s own address in gcomm address list. Bug fixed #1099478.
  • wsrep_sst_rsync would silently fail on joiner when rsync server port was already taken. Bug fixed #1099783.
  • Server would segfault on INSERT DELAYED with wsrep_replicate_myisam set to 1 due to unchecked dereference of NULL pointer. Bug fixed #1165958.
  • When grastate.dat file was not getting zeroed appropriately it would lead to RBR error during the IST. Bug fixed #1180791.
  • Due to the Provides: line in Percona XtraDB Cluster (which provides Percona-Server-server), the command yum install Percona-Server-server would install Percona XtraDB Cluster instead of the expected Percona Server. Bug fixed #1201499.
  • Replication of partition tables without binlogging enabled failed, partition truncation didn’t work because of lack of TO isolation there. Bug fixed #1219605.
  • Exception during group merge after partitioning event has been fixed. Bug fixed #1232747.
  • Default value for binlog_format is now ROW. This is done so that Percona XtraDB Cluster is not started with wrong defaults leading to non-deterministic outcomes like crash. Bug fixed #1243228.
  • CREATE TABLE AS SELECT was not replicated, if the select result set was empty. Bug fixed #1246921.
  • INSERT would return deadlock instead of duplicate key on secondary unique key collision. Bug fixed #1255147.
  • Joiner node would not initialize storage engines if rsync was used for SST and the first view was non-primary. Bug fixed #1257341.
  • Table level lock conflict resolving was releasing the wrong lock. Bug fixed #1257678.
  • Resolved the perl dependencies needed for Percona XtraDB Cluster 5.5. Bug fixed #1258563.
  • Obsolete dependencies have been removed from Percona XtraDB Cluster. Bug fixed #1259256.
  • GCache file allocation could fail if file size was a multiple of page size. Bug fixed #1259952.
  • Percona XtraDB Cluster didn’t validate the parameters of wsrep_provider_options when starting it up. Bug fixed #1260193.
  • Runtime checks have been added for dynamic variables which are Galera incompatible. Bug fixed #1262188.
  • Node would get stuck and required restart if DDL was performed after FLUSH TABLES WITH READ LOCK. Bug fixed #1265656.
  • xtrabackup-v2 is now used as default SST method in wsrep_sst_method. Bug fixed #1268837.
  • FLUSH TABLES WITH READ LOCK behavior on the same connection was changed to conform to MySQL behavior. Bug fixed #1269085.
  • Read-only detection has been added in clustercheck, which can be helpful during major upgrades (this is used by xinetd for HAProxy etc.) Bug fixed #1269469.
  • Binary log directory is now being cleanup as part of the XtraBackup SST. Bug fixed #1273368.
  • Deadlock would happen when NULL unique key was inserted. Workaround has been implemented to support NULL keys, by using the md5 sum of full row as key value. Bug fixed #1276424.

This release contains almost 100 fixed bugs, complete list of fixed bugs can be found in our release notes.

Please see the 5.5.37-25.10 releases notes for complete details on all of the new features and bug fixes. Help us improve quality by reporting any bugs you encounter using our bug tracking system. As always, thanks for your continued support of Percona!

Percona XtraDB Cluster Errata can be found in our documentation.

The post Percona XtraDB Cluster 5.5.37-25.10 is now available appeared first on MySQL Performance Blog.

Percona XtraBackup 2.2.2 beta release is now available

May 8, 2014 - 7:58am

Percona is glad to announce the release of Percona XtraBackup 2.2.2-beta1 on May 8th 2014. Downloads are available from our download site here. This BETA release, will be available in our Debian experimental and CentOS testing repositories.

This is a BETA quality release and it is not intended for production. If you want a high quality, Generally Available release, the current Stable version should be used (Percona XtraBackup 2.1.9 in the 2.1 series at the time of writing).

New Features

  • Percona XtraBackup has now been rebased on MySQL 5.6.17.
  • Percona XtraBackup package is now available for Ubuntu 14.04.

Bugs Fixed

  • Percona XtraBackup couldn’t be built with Bison 3.0. Bug fixed #1262439.
  • The xtrabackup binaries now recognize a new my.cnf option, open_files_limit. The effect is the same as for the server: it changes the maximum number of file descriptors available to the xtrabackup process. The actual limit depends on the platform and ulimit settings. Bug fixed #1183793.
  • If a remote InnoDB tablespace got CREATEd or ALTERed during the backup, an attempt to prepare such a backup later would lead to Percona XtraBackup crash. Bug fixed #1291299.
  • Code in both innobackupex and xtrabackup, that was supposed to make sure no child processes are left running in case innobackupex got killed or failed with an error, relied on the fact the SIGTERM and SIGINT signals were not blocked by the xtrabackup process. However, both SIGTERM and SIGINT might be blocked by the process that had invoked innobackupex, for example, by the Percona XtraDB Cluster server processes doing an SST, in which case they were also blocked by the xtrabackup process, since the signal mask is inherited by child processes. Fixed by replacing SIGTERM in innobackupex and SIGINT in xtrabackup auto-termination with SIGKILL. Bug fixed #1294782.

Release notes with all the bugfixes for Percona XtraBackup 2.2.2 are available in our online documentation. All of Percona‘s software is open source and free, all the details of the release can be found in the 2.2.2 milestone at Launchpad. Bugs can be reported on the launchpad bug tracker.

The post Percona XtraBackup 2.2.2 beta release is now available appeared first on MySQL Performance Blog.

Doing a rolling upgrade of Percona XtraDB Cluster from 5.5 to 5.6

May 8, 2014 - 3:00am
Overview

Percona XtraDB Cluster 5.6 has been GA for several months now and people are thinking more and more about moving from 5.5 to 5.6. Most people don’t want to upgrade all at once, but would prefer a rolling upgrade to avoid downtime and ensure 5.6 is behaving in a stable fashion before putting all of production on it. The official guide to a rolling upgrade can be found in the PXC 5.6 manual. This blog post will attempt to summarize the basic process.

However, there are a few caveats to trying to do a rolling 5.6 upgrade from 5.5:

  1. If you mix Galera 2 and Galera 3 nodes, you must set wsrep_provider_options=”socket.checksum=1″ on the Galera 3 nodes for backwards compatibility between Galera versions.
  2. You must set some 5.6 settings for 5.5 compatibility with respect to replication:
    1. You can’t enable GTID async replication on the 5.6 nodes
    2. You should use –log-bin-use-v1-row-events on the 5.6 nodes
    3. You should set binlog_checksum=NONE  on the 5.6 nodes
  3. You must not SST a 5.5 donor to a 5.6 joiner as the SST script does not handle mysql_upgrade
  4. You should set the 5.6 nodes read_only and not write to them!
The basic upgrade flow

The basic upgrade flow is:

  1. For some node(s): upgrade to 5.6, do all the above stuff, put them into a read_only pool
  2. Repeat step 1 as desired
  3. Once your 5.6 pool is sufficiently large, cut over writes to the 5.6 pool (turn off read_only, etc.) and upgrade the rest.

This is, in essence, exactly like upgrading a 5.5 master/slave cluster to 5.6 — you upgrade the slaves first, promote a slave and upgrade the master; we just have more masters to think about.

Once your upgrade is fully to 5.6, then you can go back through and remove all the 5.5 backwards compatibility

Why can’t I write to the 5.6 nodes?

The heaviest caveat is probably the fact that in a mixed 5.5 / 5.6 cluster, you are not supposed to write to the 5.6 nodes.  Why is that?  Well, the reason goes back to MySQL itself.  PXC/Galera uses standard RBR binlog events from MySQL for replication.   Replication between major MySQL versions is only ever officially supported:

  • across 1 major version (i.e., 5.5 to 5.6, though multiple version hops do often work)
  • from a lower version master to a higher version slave (i.e., 5.5 is your master and 5.6 is your slave, but not the other way around)

This compatibility requirement (which has existed for a very long time in MySQL) works great when you have a single Master replication topology, but true multi-master (multi-writer) has obviously never been considered.

Some alternativesDoes writing to the 5.6 nodes REALLY break things?

The restriction on 5.6 masters of 5.5 slaves is probably too strict in many cases.  Technically only older to newer replication is ever truly supported, but in practice you may be able to run a mixed cluster with writes to all nodes as long as you are careful.  This means (at least) that any modifications to column type formats in the newer version NOT be upgraded while the old version remains active in the cluster.  There might be other issues, I’m not sure, I cannot say I’ve tested every possible circumstance.

So, can I truly say I recommend this?  I cannot say that officially, but you may find it works fine.  As long as you acknowledge that something unforeseen may break your cluster and your migration plan, it may be reasonable.  If you decide to explore this option, please test this thoroughly and be willing to accept the consequences of it not working before trying it in production!

Using Async replication to upgrade

Another alternative is rather than trying to mix the clusters and keeping 5.6 nodes read_only, why not just setup the 5.6 cluster as an async slave of your 5.5 cluster and migrate your application to the new cluster when you are ready?  This is practically the same as maintaining a split 5.5/5.6 read_write/read_only cluster without so much risk and a smaller list of don’ts.  Cutover in this case would be effectively like promoting a 5.6 slave to master, except you would promote the 5.6 cluster.

One caveat with this approach might be dealing with replication throughput:  async may not be able to keep up replicating your 5.5 cluster writes to a separate 5.6 cluster.  Definitely check out wsrep_preordered to speed things up, it may help.  But realize some busy workloads just may not ever be able to use async into another cluster.

Just take the outage

A final alternative for this post is the idea of simply upgrading the entire cluster to 5.6 all at once during a maintenance window.  I grant that this defeats the point of a rolling upgrade, but it may offer a lot of simplicity in the longer run.

Conclusion

A rolling PXC / Galera upgrade across major MySQL versions is limited by the fact that there is no official support or reason for Oracle to support newer master to older slave.  In practice, it may work much of the time, but these situations should be considered carefully and the risk weighed against all other options.

The post Doing a rolling upgrade of Percona XtraDB Cluster from 5.5 to 5.6 appeared first on MySQL Performance Blog.

Percona XtraBackup 2.1.9 is now available

May 7, 2014 - 7:21am

Percona is glad to announce the release of Percona XtraBackup 2.1.9 on May 7th, 2014. Downloads are available from our download site here and Percona Software Repositories.

This release is the current GA (Generally Available) stable release in the 2.1 series. Percona XtraBackup is an open source, free MySQL hot backup software that performs non-blocking backups for InnoDB and XtraDB databases. Percona XtraBackup is an open source, free MySQL hot backup software that performs non-blocking backups for InnoDB and XtraDB databases.

New Features

  • Percona XtraBackup has now been rebased on MySQL 5.6.17.
  • Percona XtraBackup package is now available for Ubuntu 14.04.

Bugs Fixed

  • Percona XtraBackup couldn’t be built with Bison 3.0. Bug fixed #1262439.
  • The xtrabackup binaries now recognize a new my.cnf option, open_files_limit. The effect is the same as for the server: it changes the maximum number of file descriptors available to the xtrabackup process. The actual limit depends on the platform and ulimit settings. Bug fixed #1183793.
  • If a remote InnoDB tablespace got CREATEd or ALTERed during the backup, an attempt to prepare such a backup later would lead to Percona XtraBackup crash. Bug fixed #1291299.
  • Code in both innobackupex and xtrabackup, that was supposed to make sure no child processes are left running in case innobackupex got killed or failed with an error, relied on the fact the SIGTERM and SIGINT signals were not blocked by the xtrabackup process. However, both SIGTERM and SIGINT might be blocked by the process that had invoked innobackupex, for example, by the Percona XtraDB Cluster server processes doing an SST, in which case they were also blocked by the xtrabackup process, since the signal mask is inherited by child processes. Fixed by replacing SIGTERM in innobackupex and SIGINT in xtrabackup auto-termination with SIGKILL. Bug fixed #1294782.
  • A new table flag in the InnoDB data dictionary, introduced in MySQL 5.6.16, wasn’t recognized by Percona XtraBackup which lead to “InnoDB: in InnoDB data dictionary has unknown flags 50.” warnings. Fixed by rebasing Percona XtraBackup on MySQL 5.6.17. Bug fixed #1302882.

Release notes with all the bugfixes for Percona XtraBackup 2.1.9 are available in our online documentation. All of Percona‘s software is open source and free, all the details of the release can be found in the 2.1.9 milestone at Launchpad. Bugs can be reported on the launchpad bug tracker.

The post Percona XtraBackup 2.1.9 is now available appeared first on MySQL Performance Blog.

MySQL Audit Plugin now available in Percona Server 5.5 and 5.6

May 7, 2014 - 6:00am

The new Percona Server 5.5.37-35.0 and Percona Server 5.6.17-65.0-56, announced yesterday (May 6), both include the open source version of the MySQL Audit Plugin. The MySQL Audit Plugin is used to log all queries or connections (“audit” MySQL usage). Until yesterday’s release, the MySQL Audit Plugin was only available in MySQL Enterprise.

Logging all MySQL usage is very important for a number of applications, for example:

  • Required: applications which deals with sensitive data (credit cards, medical records, etc); required for security compliances (i.e. HIPAA)
  • Very helpful: multi-tenants applications or MySQL as a service; MySQL administrators can audit the MySQL usage from the security and performance standpoint
  • Very helpful: investigating and troubleshooting; it is great to have a full log of all queries, which can help a lot for troubleshooting of MySQL and even for performance audit.

Originally, the only “easy” option was to enable general log. (Other options included using binary logs which does not include select queries or enabling queries “trace” in the application or MySQL connector). However, logging all queries using a general log may dramatically decrease performance in the highly loaded MySQL applications: Aleksandr Kuzminsky published a benchmark in 2009 to show the overhead of MySQL general and slow log. The main benefit of MySQL Log Audit plugin is that it logs all queries asynchronously (can be changed in the config). I’ve decided to try the new audit plugin in Percona Server and measure the performance impact of the new plugin compared to enabling the general log for the CPU bound applications.

How to start with MySQL Audit Plugin

First, we will need to enable (or “install”) MySQL audit plugin as decribed in the doc:

mysql> select version(); +-------------+ | version() | +-------------+ | 5.5.37-35.0 | +-------------+ 1 row in set (0.00 sec) mysql> INSTALL PLUGIN audit_log SONAME 'audit_log.so'; Query OK, 0 rows affected (0.00 sec)

Now can see all MySQL audit plugin options:

mysql> show global variables like '%audit%'; +--------------------------+--------------+ | Variable_name | Value | +--------------------------+--------------+ | audit_log_buffer_size | 1048576 | | audit_log_file | audit.log | | audit_log_flush | OFF | | audit_log_format | OLD | | audit_log_policy | ALL | | audit_log_rotate_on_size | 0 | | audit_log_rotations | 0 | | audit_log_strategy | ASYNCHRONOUS | +--------------------------+--------------+ 8 rows in set (0.00 sec)

There are a bunch of options we can tweak here, the most important for MySQL performance are:

  • audit_log_buffer_size; this buffer is used to cache the queries (for asynchronous operation).
  • audit_log_strategy; All options are listed in the documentation page:
ValueMeaningASYNCHRONOUSLog asynchronously, wait for space in output bufferPERFORMANCELog asynchronously, drop request if insufficient space in output bufferSEMISYNCHRONOUSLog synchronously, permit caching by operating systemSYNCHRONOUSLog synchronously, call sync() after each request

The most useful option in my mind is ASYNCHRONOUS, providing us with good balance between performance and not loosing transactions if the output buffer is not large enough.

  •  audit_log_policy; we can log all queries or MySQL logins only (very useful if we only need to audit MySQL connections)

Open Source Audit Plugin in MySQL Community server

You can also use Percona Open Source version of Audit Plugin in MySQL community version (5.5.37 and 5.6.17). Simply download the linux tarball of Percona Server and copy the  audit_log.so to your MySQL plugin dir.

Find plugin dir:

mysql> show global variables like '%plugin%'; +---------------+------------------------------+ | Variable_name | Value | +---------------+------------------------------+ | plugin_dir | /usr/local/mysql/lib/plugin/ | +---------------+------------------------------+ 1 row in set (0.00 sec)

Copy the file:

# cp audit_log.so /usr/local/mysql/lib/plugin/

Install plugin:

Server version: 5.5.37 MySQL Community Server (GPL) mysql> INSTALL PLUGIN audit_log SONAME 'audit_log.so'; Query OK, 0 rows affected (0.00 sec) Server version: 5.6.17 MySQL Community Server (GPL) mysql> INSTALL PLUGIN audit_log SONAME 'audit_log.so'; Query OK, 0 rows affected (0.00 sec)

Using MySQL audit plugin

When plugin is enabled, it will log entries in audit.log file in XML format. Example:

<AUDIT_RECORD "NAME"="Audit" "RECORD"="1_2014-04-30T00:04:42" "TIMESTAMP"="2014-04-30T00:04:42 UTC" "MYSQL_VERSION"="5.5.37-35.0" "STARTUP_OPTIONS"="--basedir=/usr --datadir=/var/lib/mysql --plugin-dir=/usr/lib64/mysql/plugin --user=mysql --log-error=/var/log/mysqld.log --pid-file=/var/lib/mysql/localhost.localdomain.pid --socket=/var/lib/mysql/mysql.sock" "OS_VERSION"="x86_64-Linux", /> <AUDIT_RECORD "NAME"="Query" "RECORD"="2_2014-04-30T00:04:42" "TIMESTAMP"="2014-04-30T00:04:42 UTC" "COMMAND_CLASS"="install_plugin" "CONNECTION_ID"="1" "STATUS"="0" "SQLTEXT"="INSTALL PLUGIN audit_log SONAME 'audit_log.so'" "USER"="root[root] @ localhost []" "HOST"="localhost" "OS_USER"="" "IP"="" /> <AUDIT_RECORD "NAME"="Query" "RECORD"="3_2014-04-30T00:04:42" "TIMESTAMP"="2014-04-30T00:05:07 UTC" "COMMAND_CLASS"="show_variables" "CONNECTION_ID"="1" "STATUS"="0" "SQLTEXT"="show global variables like '%audit%'" "USER"="root[root] @ localhost []" "HOST"="localhost" "OS_USER"="" "IP"="" />

<AUDIT_RECORD "NAME"="Query" "RECORD"="10_2014-04-30T00:04:42" "TIMESTAMP"="2014-04-30T12:33:20 UTC" "COMMAND_CLASS"="grant" "CONNECTION_ID"="2" "STATUS"="0" "SQLTEXT"="grant all on sbtest.* to sb@localhost identified by 'sb'" "USER"="root[root] @ localhost []" "HOST"="localhost" "OS_USER"="" "IP"="" /> <AUDIT_RECORD "NAME"="Connect" "RECORD"="11_2014-04-30T00:04:42" "TIMESTAMP"="2014-04-30T12:34:53 UTC" "CONNECTION_ID"="3" "STATUS"="0" "USER"="sb" "PRIV_USER"="sb" "OS_LOGIN"="" "PROXY_USER"="" "HOST"="localhost" "IP"="" "DB"="sbtest" /> <AUDIT_RECORD "NAME"="Query" "RECORD"="1292_2014-04-30T00:04:42" "TIMESTAMP"="2014-04-30T12:45:07 UTC" "COMMAND_CLASS"="select" "CONNECTION_ID"="32" "STATUS"="1146" "SQLTEXT"="SELECT pad FROM sbtest8 WHERE id=5036031" "USER"="sb[sb] @ localhost []" "HOST"="localhost" "OS_USER"="" "IP"="" />

 Important notes: 

  • As all queries will be logged here, the passwords from “GRANT” will also be saved in clear text (as you can see above). It is very important to secure the file on disk.
  • The file can grow very large on disk:

ls -lah /var/lib/mysql/audit.log -rw-rw---- 1 mysql mysql 7.1G May 4 07:30 /var/lib/mysql/audit.log

Searching the Audit Log entries

MySQL utilities provide a useful tool, mysqlauditgrep, to search / grep the logs file.  Unfortunately, I was not able to make it work (tried both v. 1.3 and v 1.4)  with audit plugin format created by Percona server. According to this bug  it can’t parse the “new” audit format. In my case, mysqlauditgrep will return a parsing error when I use the default format and returned no results when I set the “audit_log_format=NEW”. It will be nice to use the mysqlauditgrep as it looks like a very powerful tool, but for now our searching options are limited to conventional linux grep (which is not very easy for XML documents) or custom application to parse/search XML.

Performance overhead of Audit Log Plugin and General Log 

Finally, I wanted to measure the overhead of the Audit Log Plugin compared to General Log. I did a quick benchmark with sysbench OLTP test (CPU bound workload) with 4 modes:

  1. Audit Plugin disabled (to measure baseline)
  2. Audit Plugin enabled and logs all queries
  3. Audit Plugin enabled and logs only logins
  4. General Log enabled, Audit Plugin disabled

Here are the results:

TestOverheadPlugin +  audit_log_policy = ALL~15% overheadPlugin +  audit_log_policy = LOGINS~0% overhead (sysbench only connects once, so there may be bigger overhead here)General_log~62% overhead

As we can see here, audit log is not free from overhead, however, it is much smaller than enabling general_log to log all and every query. Those are quick benchmark results and more tests are need for more accurate measurements. Also, as always, your milage can vary.

Nice to have features

What I would love to have for audit plugin is the ability to log only some specific actions. For example, only log activity from a specific user or access to a specific table (i.e. a table with a sensitive data), etc. This will give more control and less overhead (=better performance).

Conclusion

The MySQL Audit Plugin is a great feature – it is a valuable tool for MySQL security and performance audits. The performance overhead may be a concern for a highly loaded systems, however, it looks reasonable and is much better than using general log to log all queries.

If you use general log or any other audit plugins, please share your experience in the comments.

The post MySQL Audit Plugin now available in Percona Server 5.5 and 5.6 appeared first on MySQL Performance Blog.

Percona Server 5.6.17-65.0 is now available

May 6, 2014 - 9:50am

Percona Server version 5.6.17-65.0

Percona is glad to announce the release of Percona Server 5.6.17-65.0 on May 6th, 2014. Downloads are available here and from the Percona Software Repositories.

Based on MySQL 5.6.17, including all the bug fixes in it, Percona Server 5.6.17-65.0 is the current GA release in the Percona Server 5.6 series. All of Percona’s software is open-source and free, all the details of the release can be found in the 5.6.17-65.0 milestone at Launchpad.

New Features:

  • Percona Server now supports Metrics for scalability measurement.
  • Percona Server now supports Audit Log Plugin.
  • Percona Server parser and query optimizer now support Multiple Clustering Keys when TokuDB engine is used.
  • Storage engine handler interface has been extended with new calls to notify the storage engine of imminent table or index scan. The calls are used by TokuDB to improve performance of these operations.
  • Percona Server packages are now available for Ubuntu 14.04.

Bugs Fixed:

  • Percona Server couldn’t be built with Bison 3.0. Bug fixed #1262439, upstream #71250 (Ryan Gordon).
  • Fixed the inadequate background LRU flushing for write workloads with InnoDB compression that could lead to lower performance. Bug fixed #1295268.
  • Percona Server debug packages were not built for the previous releases. Bug fixed #1298352.
  • Queries that no longer exceed long_query_time were written to the slow query log if they matched the previous long_query_time value when slow_query_log_use_global_control variable was set to all. Bug fixed #1016991.
  • When writing audit plugins it was not possible to get notifications for general-log events without enabling the general-log. Bug fixed #1182535 (upstream #60782).
  • mysqld_safe did not correctly parse flush_caches and numa_interleave options. Bug fixed #1231110.
  • Thread Pool would handle a new client connection without notifying Audit Plugin. Bug fixed #1282008.
  • Fixed a performance issue in extending tablespaces if running under fusionIO with atomic writes enabled. Bug fixed #1286114 (Jan Lindström).
  • Previous implementation of the log_slow_rate_type set to query with log_slow_rate_limit feature would log every nth query deterministically instead of each query having a 1/n probability to get logged. Fixed by randomly selecting the queries to be logged instead of logging every nth query. Bug fixed #1287650.
  • Percona Server source files were referencing Maatkit instead of Percona Toolkit. Bug fixed #1174779.
  • Maximum allowed value for log_slow_rate_limit was ULONG_MAX (ie. either 4294967295 or 18446744073709551615, depending on the platform). As it was unreasonable to configure the slow log for every four billionth session/query, new maximum allowed value is set to 1000. Bug fixed #1290714.

Other bugs fixed #1295523, #1299688 (upstream #72163) and #1272732.

Release notes for Percona Server 5.6.17-65.0 are available in our online documentation. Bugs can be reported on the launchpad bug tracker.

The post Percona Server 5.6.17-65.0 is now available appeared first on MySQL Performance Blog.

Percona Server 5.5.37-35.0 is now available

May 6, 2014 - 9:47am

Percona Server version 5.5.37-35.0

Percona is glad to announce the release of Percona Server 5.5.37-35.0 on May 6th, 2014 (Downloads are available here and from the Percona Software Repositories). Based on MySQL 5.5.37, including all the bug fixes in it, Percona Server 5.5.37-35.0 is now the current stable release in the 5.5 series. All of Percona‘s software is open-source and free, all the details of the release can be found in the 5.5.37-35.0 milestone at Launchpad.

New Features:

Bugs Fixed:

  • Percona Server couldn’t be built with Bison 3.0. Bug fixed #1262439, upstream #71250.
  • Backported the upstream fix for overflow which would caused replication SQL thread to fail to execute events. Bug fixed #1070255 (upstream #67352).
  • Percona Server debug packages were not built for the previous releases. Bug fixed #1298352.
  • Queries that no longer exceed long_query_time were written to the slow query log if they matched the previous long_query_time value when slow_query_log_use_global_control variable was set to all. Bug fixed #1016991.
  • When writing audit plugins it was not possible to get notifications for general-log events without enabling the general-log. Bug fixed #1182535 (upstream #60782).
  • mysqld_safe did not correctly parse flush_caches and numa_interleave options. Bug fixed #1231110.
  • Thread Pool would handle a new client connection without notifying Audit Plugin. Bug fixed #1282008.
  • Fixed a performance issue in extending tablespaces if running under fusionIO with atomic writes enabled. Bug fixed #1286114 (Jan Lindström).
  • Previous implementation of the log_slow_rate_type set to query with log_slow_rate_limit feature would log every nth query deterministically instead of each query having a 1/n probability to get logged. Fixed by randomly selecting the queries to be logged instead of logging every nth query. Bug fixed #1287650.
  • Percona Server source files were referencing Maatkit instead of Percona Toolkit. Bug fixed #1174779.
  • Maximum allowed value for log_slow_rate_limit was ULONG_MAX (ie. either 4294967295 or 18446744073709551615, depending on the platform). As it was unreasonable to configure the slow log for every four billionth session/query, new maximum allowed value is set to 1000. Bug fixed #1290714.

Other bugs fixed: #1272732.
Release notes for Percona Server 5.5.37-35.0 are available in our online documentation. Bugs can be reported on the launchpad bug tracker.

The post Percona Server 5.5.37-35.0 is now available appeared first on MySQL Performance Blog.

Row-based replication, MySQL 5.6 upgrades and temporal data types

May 6, 2014 - 8:31am
Whither your rollback plan?

MySQL 5.6 upgrades are in full swing these days and knowing how to safely upgrade from MySQL 5.5 to 5.6 is important. When upgrading a replication environment, it’s important that you can build a migration plan that safely allows for your upgrade with minimal risk — rollback is often a very important component to this.

For many people this means upgrading slaves first and then the master.  The strategy of an older master replicating to a newer slave is well known and has been supported in MySQL replication for a very long time.  To be specific:  you can have a MySQL 5.6 slave of a 5.5 master and this should work fine until you upgrade your master and/or promote one of the slaves to be the master.

However, there are those of us who like to live on the edge and do unsupported things.  Suppose that when you cut over to that MySQL 5.6 master your application completely breaks.  What would your rollback plan be?   In such a case, leaving a 5.5 slave of the new 5.6 master (or perhaps a dual-master setup with 5.5 and 5.6) would be useful to allow you to rollback to but still have the data written on the 5.6 master.

What might break?

With Statement-based replication (SBR), you are generally ok with this type of setup, provided you aren’t doing any MySQL 5.6 syntax-specific things until you don’t have any more 5.5 slaves.  However, with Row-based replication (RBR), things are a bit trickier, particularly when column formats change.

Now, one nice new feature of MySQL 5.6 is the improvement of the storage requirements for DATETIME fields as well as the addition of fractional second support for TIME, DATETIME, and TIMESTAMP.   This is great, but unfortunately this is a new column format that 5.5 clearly would not understand.  Does this put our 5.6 to 5.5 replication in jeopardy?    The answer is, if we’re careful, NO.

Quite simply, MySQL 5.6 supports both old and new types and mysql_upgrade does not make such a conversion on existing tables.  Only NEW tables or REBUILT tables in 5.6 will use the new format.  Any tables from 5.5 with a simple mysql_upgrade to 5.6 will still be using the old types.  For more information on how to find columns in 5.6 that are using the old format, see Ike Walker’s excellent blog post on the topic.  (Thanks Ike!)

An imperfect test

To test this out, I created a simple experiment.  I have a master and slave using RBR, both on 5.5, and I setup pt-heartbeat to update the master.  I realized that pt-heartbeat actually uses a varchar for the timestamp field — I suspect this makes multiple database support easier.  However, since pt-heartbeat’s update uses a NOW() to populate that field, I can convert it to a DATETIME:

[root@master ~]# pt-heartbeat --update  --database percona --create-table CREATE TABLE `heartbeat` ( `ts` varchar(26) NOT NULL, `server_id` int(10) unsigned NOT NULL, `file` varchar(255) DEFAULT NULL, `position` bigint(20) unsigned DEFAULT NULL, `relay_master_log_file` varchar(255) DEFAULT NULL, `exec_master_log_pos` bigint(20) unsigned DEFAULT NULL, PRIMARY KEY (`server_id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 master mysql> alter table heartbeat drop column ts, add column ts DATETIME; slave mysql> select * from heartbeat\G *************************** 1. row *************************** server_id: 1 file: master-bin.000002 position: 5107583 relay_master_log_file: NULL exec_master_log_pos: NULL ts: 2014-05-02 17:03:59 1 row in set (0.00 sec) CREATE TABLE `heartbeat` ( `server_id` int(10) unsigned NOT NULL, `file` varchar(255) DEFAULT NULL, `position` bigint(20) unsigned DEFAULT NULL, `relay_master_log_file` varchar(255) DEFAULT NULL, `exec_master_log_pos` bigint(20) unsigned DEFAULT NULL, `ts` datetime DEFAULT NULL, PRIMARY KEY (`server_id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 

So my heartbeat table now has a 5.5 DATETIME, pt-heartbeat is working properly, and the heartbeat is replicating to the slave.  Now I will upgrade my master to MySQL 5.6:

[root@master ~]# rpm -e Percona-Server-devel-55-5.5.36-rel34.2.el6.x86_64 Percona-Server-shared-55-5.5.36-rel34.2.el6.x86_64 Percona-Server-client-55-5.5.36-rel34.2.el6.x86_64 Percona-Server-server-55-5.5.36-rel34.2.el6.x86_64 --nodeps [root@master ~]# yum install Percona-Server-server-56.x86_64 ============================================================================================================== Package Arch Version Repository Size ============================================================================================================== Installing: Percona-Server-server-56 x86_64 5.6.16-rel64.2.el6 Percona 19 M Installing for dependencies: Percona-Server-client-56 x86_64 5.6.16-rel64.2.el6 Percona 6.8 M Percona-Server-shared-56 x86_64 5.6.16-rel64.2.el6 Percona 712 k Transaction Summary ============================================================================================================== Install 3 Package(s) ... [root@master ~]# service mysql start Starting MySQL (Percona Server)....... SUCCESS! [root@master ~]# mysql Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 1 Server version: 5.6.16-64.2-56-log Percona Server (GPL), Release 64.2, Revision 569 [root@master ~]# mysql_upgrade Looking for 'mysql' as: mysql Looking for 'mysqlcheck' as: mysqlcheck Running 'mysqlcheck with default connection arguments Running 'mysqlcheck with default connection arguments mysql.columns_priv OK mysql.db OK mysql.event OK mysql.func OK mysql.general_log OK mysql.help_category OK mysql.help_keyword OK mysql.help_relation OK mysql.help_topic OK mysql.host OK mysql.ndb_binlog_index OK mysql.plugin OK mysql.proc OK mysql.procs_priv OK mysql.proxies_priv OK mysql.servers OK mysql.slow_log OK mysql.tables_priv OK mysql.time_zone OK mysql.time_zone_leap_second OK mysql.time_zone_name OK mysql.time_zone_transition OK mysql.time_zone_transition_type OK mysql.user OK Running 'mysql_fix_privilege_tables'... Running 'mysqlcheck with default connection arguments Running 'mysqlcheck with default connection arguments percona.heartbeat OK OK

I can now verify that Ike’s INFORMATION_SCHEMA queries correctly detect the ‘heartbeat.ts’ column as the old format:

master mysql> select t.table_schema,t.engine,t.table_name,c.column_name,c.column_type from information_schema.tables t inner join information_schema.columns c on c.table_schema = t.table_schema and c.table_name = t.table_name left outer join information_schema.innodb_sys_tables ist on ist.name = concat(t.table_schema,'/',t.table_name) left outer join information_schema.innodb_sys_columns isc on isc.table_id = ist.table_id and isc.name = c.column_name where c.column_type in ('time','timestamp','datetime') and t.table_schema not in ('mysql','information_schema','performance_schema') and t.table_type = 'base table' and (t.engine != 'innodb' or (t.engine = 'innodb' and isc.mtype = 6)) order by t.table_schema,t.table_name,c.column_name; +--------------+--------+------------+-------------+-------------+ | table_schema | engine | table_name | column_name | column_type | +--------------+--------+------------+-------------+-------------+ | percona | InnoDB | heartbeat | ts | datetime | +--------------+--------+------------+-------------+-------------+ 1 row in set (0.04 sec)

To make replication work from MySQL 5.6 to 5.5, I also had to add a few backwards compatibility options on the master:

log_bin_use_v1_row_events = ON binlog_checksum = NONE

Once I fixed that up, I can verify my slave is still working after this and receiving heartbeats. Clearly the new formats are not a show-stopper for backwards replication compatibility.

slave mysql> show slave status\G *************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: 192.168.70.2 Master_User: repl Master_Port: 3306 Connect_Retry: 60 Master_Log_File: master-bin.000005 Read_Master_Log_Pos: 120 Relay_Log_File: slave-relay-bin.000002 Relay_Log_Pos: 267 Relay_Master_Log_File: master-bin.000005 Slave_IO_Running: Yes Slave_SQL_Running: Yes master mysql> select * from heartbeat; +-----------+-------------------+----------+-----------------------+---------------------+---------------------+ | server_id | file | position | relay_master_log_file | exec_master_log_pos | ts | +-----------+-------------------+----------+-----------------------+---------------------+---------------------+ | 1 | master-bin.000002 | 5115935 | NULL | NULL | 2014-05-02 17:04:23 | +-----------+-------------------+----------+-----------------------+---------------------+---------------------+ 1 row in set (0.01 sec) slave mysql> select * from heartbeat; +-----------+-------------------+----------+-----------------------+---------------------+---------------------+ | server_id | file | position | relay_master_log_file | exec_master_log_pos | ts | +-----------+-------------------+----------+-----------------------+---------------------+---------------------+ | 1 | master-bin.000002 | 5115935 | NULL | NULL | 2014-05-02 17:04:23 | +-----------+-------------------+----------+-----------------------+---------------------+---------------------+ 1 row in set (0.00 sec)

But, if I’m not careful on MySQL 5.6, and rebuild the table, the new format does clearly bite me:

master mysql> set sql_log_bin=0; Query OK, 0 rows affected (0.00 sec) master mysql> alter table percona.heartbeat force; Query OK, 1 row affected, 1 warning (0.18 sec) Records: 1 Duplicates: 0 Warnings: 1 master mysql> show warnings; +-------+------+-------------------------------------------------------------------------------------+ | Level | Code | Message | +-------+------+-------------------------------------------------------------------------------------+ | Note | 1880 | TIME/TIMESTAMP/DATETIME columns of old format have been upgraded to the new format. | +-------+------+-------------------------------------------------------------------------------------+ 1 row in set (0.00 sec) slave mysql> show slave status\G *************************** 1. row *************************** ... Slave_IO_Running: Yes Slave_SQL_Running: No ... Last_Errno: 1677 Last_Error: Column 5 of table 'percona.heartbeat' cannot be converted from type '' to type 'datetime' ... Last_SQL_Errno: 1677 Last_SQL_Error: Column 5 of table 'percona.heartbeat' cannot be converted from type '' to type 'datetime' Replicate_Ignore_Server_Ids: Master_Server_Id: 1 1 row in set (0.00 sec)

TL;DR

What does all this teach us?

While the MySQL version is important, for RBR what matters most is the actual current format for each column.  Your master and slave(s) MUST have the same column formats for RBR to work right.

So, the new temporal formats do not necessarily break RBR replication back to 5.5, provided:

  • All base MySQL 5.6 enhancements to replication are disabled (binlog checksums and the RBR v2 format)
  • Tables with temporal formats are preserved in their 5.5 formats until all 5.5 nodes are retired.
  • You can avoid creating any new tables on the MySQL 5.6 master with temporal formats

However, I want  to make it clear that MySQL 5.6 to 5.5 replication is technically unsupported.  I have not exhausted all possibilities for problems with 5.6 to 5.5 RBR replication, just this specific one. If you choose to make an upgrade strategy that relies on backwards replication in this way, be prepared for it to not work and test it thoroughly in advance.  The purpose of this post is to simply point out that data type formats, in and of themselves, do not necessarily break RBR backwards compatibility.

The post Row-based replication, MySQL 5.6 upgrades and temporal data types appeared first on MySQL Performance Blog.

Exploring message brokers

May 5, 2014 - 5:00am

Message brokers are not regularly covered here but are, nonetheless, important web-related technologies. Some time ago, I was asked by one of our customer to review a selection of OSS message brokers and propose a couple of good candidates. The requirements were fairly simple: behave well when there’s a large backlog of messages, be able to create a cluster and in case of the failure of a node in a cluster, try to protect the data but never blocks the publishers even though that might imply data lost. Nothing fancy regarding queues and topics management. I decided to write my findings here, before I forget…

I don’t consider myself a message broker specialist and I spent only about a day or two on each so, I may have done some big mistakes configuration wise. I’ll take the blame if something is misconfigured or not used correctly.

RabbitMQ

RabbitMQ is well known and popular message broker and it has many powerful features. The documentation on the RabbitMQ web site is excellent and there are many books available. RabbitMQ is written in Erlang, not a widely used programming language but well adapted to such tasks. The company Pivotal develops and maintains RabbitMQ. I reviewed version 3.2.2 on CentOS 6 servers.

The installation was easy, I installed Erlang version R14B from epel and the RabbitMQ rpm. The only small issue I had was that the server is expecting “127.0.0.1″ to be resolved in /etc/hosts and the openstack VMs I used were missing that. Easy to fix. I also installed and enabled the management plugin.

The RabbitMQ configuration is set in the rabbitmq.config file and it has tons of adjustable parameters. I used the defaults. In term of client API, RabbitMQ support a long list of languages and some standards protocols, like STOMP are available with a plugin. Queues and topics can be created either by the web interface or through the client API directly. If you have more than one node, they can be clustered and then, queues and topics, can be replicated to other servers.

I created 4 queues, wrote a ruby client and started inserting messages. I got a publishing rate of about 20k/s using multiple threads but I got a few stalls caused by the vm_memory_high_watermark, from my understanding during those stalls it writing to disk. Not exactly awesome given my requirements. Also, some part is always kept in memory even if a queue is durable so, even though I had plenty of disk space, the memory usage grew and eventually hit the vm_memory_high_watermark setting. The cpu load was pretty high during the load, between 40% and 50% on an 8 cores VM.

Even though my requirements were not met, I setup a replicated queue on 2 nodes and inserted a few millions objects. I killed one of the two nodes and insert were even faster but then… I did a mistake. I restarted the node and asked for a resync. Either I didn’t set it correctly or the resync is poorly implemented but it took forever to resync and it was slowing down as it progressed. At 58% done, it has been running for 17h, one thread at 100%. My patience was exhausted.

So, lots of feature, decent performance but behavior not compatible with the requirements.

Kafka

Kafka has been designed originally by LinkedIn, it is written in Java and it is now under the Apache project umbrella. Sometimes you look at a technology and you just say: wow, this is really done the way it should be. At least I could say that for the purpose I had. What is so special about Kafka is the architecture, it stores the messages in flat files and consumers ask messages based on an offset. Think of it like a MySQL server (producer) saving messages (updates SQL) to its binlogs and slaves (consumers) ask messages based on an offset. The server is pretty simple and just don’t care about the consumers much. That simplicity makes it super fast and low on resource. Old messages can be retained on a time base (like expire_logs_days) and/or on a storage usage base.

So, if the server doesn’t keep track of what has been consumed on each topics, how do can you have multiple consumer. The missing element here is Zookeeper. The Kafka server uses Zookeeper for cluster membership and routing while the consumers can also use Zookeeper or something else for synchronization. The sample consumer provided with the server uses Zookeeper so you can launch many instances and they’ll synchronize automatically. For the ones that doesn’t know Zookeeper, it is a highly-available synchronous distributed storage system. If you know Corosync, it provides somewhat the same functionality.

Feature wise Kafka, isn’t that great. There’s no web frontend builtin although a few are available in the ecosystem. Routing and rules are inexistent and stats are just with JMX. But, the performance… I reached a publishing speed of 165k messages/s over a single thread, I didn’t bother tuning for more. Consuming was essentially disk bound on the server, 3M messages/s… amazing. That was without Zookeeker coordination. Memory and cpu usage were modest.

To test clustering, I created a replicated queue, inserted a few messages, stopped a replica, inserted a few millions more messages and restarted the replica. I took only a few seconds to resync.

So, Kafka is very good fit for the requirements, stellar performance, low resource usage and nice fit with the requirements.

ActiveMQ

ActiveMQ is another big player in the field with an impressive feature set. ActiveMQ is more in the RabbitMQ league than Kafka and like Kafka, it is written in Java. HA can be provided by the storage backend, levelDB supports replication but I got some issues with it. My requirements are not for full HA, just to make sure the publishers are never blocked so I dropped the storage backend replication in favor of a mesh of brokers.

My understanding of the mesh of brokers is that you connect to one of the members and you publish or consume a message. You don’t know on which node(s) the queue is located, the broker you connect to knows and routes your request. To further help, you can specify all the brokers on the connection string and the client library will just reconnect to another if the one you are connected to goes down. That looks pretty good for the requirements.

With the mesh of brokers setup, I got an insert rate of about 5000 msg/s over 15 threads and a single consumer was able to read 2000 msg/s. I let it run for a while and got 150M messages. At this point though, I lost the web interface and the publishing rate was much slower.

So, a big beast, lot of features, decent performance, on the edge with the requirements.

Kestrel

Kestrel is another interesting broker, this time, more like Kafka. Written in scala, the Kestrel broker speaks the memcached protocol. Basically, the key becomes the queue name and the object is the message. Kestrel is very simple, queues are defined in a configuration file but you can specify, per queue, storage limits, expiration and behavior when limits are reached. With a setting like “discardOldWhenFull = true”, my requirement of never blocking the publishers is easily met.

In term of clustering Kestrel is a bit limited but each can publish its availability to Zookeeper so that publishers and consumers can be informed of a missing server and adjust. Of course, if you have many Kestrel servers with the same queue defined, the consumers will need to query all of the broker to get the message back and strict ordering can be a bit hard.

In term of performance, a few simple bash scripts using nc to publish messages easily reached 10k messages/s which is very good. The rate is static over time and likely limited by the reconnection for each message. The presence of consumers slightly reduces the publishing rate but nothing drastic. The only issue I had was when a large number of messages expired, the server froze for some time but that was because I forgot to set maxExpireSweep to something like 100 and all the messages were removed in one pass.

So, fairly good impression on Kestrel, simple but works well.

Conclusion

For the requirements given by the customer, Kafka was like a natural fit. It offers a high guarantee that the service will be available and non-blocking under any circumstances. In addition, messages can easily be replicated for higher data availability. Kafka performance is just great and resource usage modest.

The post Exploring message brokers appeared first on MySQL Performance Blog.

The top 9 Percona Toolkit tools that can make your job easier: May 7 Webinar

May 5, 2014 - 3:00am

Tools for MySQL are a vital part of any deployment, so it’s important to use ones that are reliable and well-designed. Percona Toolkit is a collection of more than 30 command-line tools for MySQL, Percona Server, and MariaDB that can help database administrators automate a variety of database and system tasks. With so many available tools, however, it can be difficult knowing where to start.

For this reason I invite you to join me on Wednesday, May 7 at 10 a.m. Pacific time for a free webinar titled, “The top 9 Percona Toolkit tools that can make your job easier.” You can register directly here (you’ll also be able to download the slides and catch the recording following the webinar at that same link).

Spoiler alert!  The 9 most popular tools in Percona Toolkit are:

Percona Toolkit for MySQL is derived from Maatkit and Aspersa, two of the best-known MySQL management software utility toolkits for MySQL server administration. It has been downloaded more than 250,000 times. Some of the best-known Internet sites powered by MySQL, Percona Server, MariaDB, and Amazon RDS use tools from Percona Toolkit for MySQL to manage their databases. If you have never heard of Percona Toolkit or if you have but are still new to it, this webinar will orient you to the tools and help you get the most out of them.

I’ll also be fielding questions at the end of the webinar. I recommend registering now to reserve your spot – see you Wednesday!

The post The top 9 Percona Toolkit tools that can make your job easier: May 7 Webinar appeared first on MySQL Performance Blog.

Pages

Contact Us 24 Hours A Day
Support Contact us 24×7
Emergency? Contact us for help now!
Sales North America (888) 316-9775 or
(208) 473-2904
Sales
Europe
+44-208-133-0309 (UK)
0-800-051-8984 (UK Toll Free)
0-800-181-0665 (GER Toll Free)
More Numbers
Training (855) 55TRAIN or
(925) 271-5054

 

Share This
]]>