How easy is it to identify and debug Percona XtraDB Cluster replication problem ? If you are using PXC, you may have already seen in your datadirectory several log files starting with GRA_ Those files correspond to a replication failure. That means the slave thread was not able to apply one transaction. For each of […]
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The principal source of information for InnoDB diagnostics is the output of SHOW ENGINE INNODB STATUS but there are some sections that are not very useful. For example, LATEST DETECTED DEADLOCK only shows, as the name implies, the latest error detected. If you have 100 deadlocks per minute you will be able to see only […]
Percona XtraDB Cluster (PXC) and the technology it uses (Galera) is an exciting alternative to traditional MySQL replication. For those who don’t know, it gives you: Fully Synchronous replication with a write latency increase equivalent to a ping RTT to the furthest node Automatic cluster synchronization, both incremental and full restores The ability to read […]
During the design period of a new cluster, it is always advised to have at least 3 nodes (this is the case with PXC but it’s also the same with PRM). But why and what are the risks ? The goal of having more than 2 nodes, in fact an odd number is recommended in […]
I frequently see questions about how to understand the nature of errors in MySQL’s error log. Now, there is a lot of complexity to this — the flowchart would be quite large, as with any nontrivial piece of software. But there is one particular class of errors that is relatively easy to diagnose, if you […]
Not everyone may know this, but there are precious few innodb crash recovery tests available. Some folks have noticed this and asked for something to be done about it, but unfortunately, no tests have been created for the main MySQL branch. The MySQL at Facebook branch has a number of tests that are quite interesting. […]
It is no secret that bugs related to multithreading–deadlocks, data races, starvations etc–have a big impact on application’s stability and are at the same time hard to find due to their nondeterministic nature. Any tool that makes finding such bugs easier, preferably before anybody is aware of their existence, is very welcome.
I wrote about MySQL Error Messages before and as you might guess I’m not very happy with quality for error messages it produces. Now I’m revisiting this subject with couple of more annoying examples I ran into during last couple of days.
mysql> drop database test;
ERROR 1010 (HY000): Error dropping database (can't rmdir './test/', errno: 17)
You know how in addition to the main movie you have extras on the DVD.Â Extra commentary, bloopers, extra scenes, etc? Well welcome the Tyrant extras.Â With my previous blog posts I was trying to set-up a case for looking at NOSQL tools, and not meant to be a decision making tool.Â Each solution has […]
As Calpont announced availability of InfiniDB I surely couldn’t miss a chance to compare it with previously tested databases in the same environment. See my previous posts on this topic: Analyzing air traffic performance with InfoBright and MonetDB Air traffic queries in LucidDB I could not run all queries against InfiniDB and I met some […]