Author - Krunal Bauskar

Improved wsrep-stages and related instrumentation in Percona XtraDB Cluster

wsrep-stages

In this blog post, we’ll look at how we’ve improved wsrep-stages and related instrumentation in Percona XtraDB Cluster.
Introduction
When you execute a workload and need to find out what the given thread is working on, “SHOW PROCESSLIST” comes to the top of your mind. It is an effective way to track the thread status. We decided […]

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Percona XtraDB Cluster Transaction Replay Anomaly

wsrep-stages

In this blog post, we’ll look at a transaction replay anomaly in Percona XtraDB Cluster.
Introduction
Percona XtraDB Cluster/Galera replays a transaction if the data is non-conflicting but, the transaction happens to have conflicting locks.
Anomaly
Let’s understand this with an example:

Let’s assume a two-node cluster (node-1 and node-2)
Base table “t” is created as follows:

Shell

create database test;
use test;
create […]

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BEWARE: Increasing fc_limit can affect SELECT latency

SELECT Latency

In this blog post, we’ll look at how increasing the fc_limit can affect SELECT latency.
Introduction
Recent Percona XtraDB Cluster optimizations have exposed fc_limit contention. It was always there, but was never exposed as the Commit Monitor contention was more significant. As it happens with any optimization, once we solve the bigger contention issues, smaller contention […]

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Tracking IST Progress in Percona XtraDB Cluster

wsrep-stages

In this blog post, we’ll look at how Percona XtraDB Cluster uses IST.
Introduction
Percona XtraDB Cluster uses the concept of an Incremental State Transfer (IST). When a node of the cluster leaves the cluster for a short period of time, it can rejoin the cluster by getting the delta set of missing changes from any active node […]

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More Trackable Flow Control for Percona XtraDB Cluster

wsrep-stages

In this blog post, we’ll discuss trackable flow control in Percona XtraDB Cluster.
Introduction
Percona XtraDB Cluster has a self-regulating mechanism called Flow Control. This mechanism helps to avoid a situation wherein the weakest/slowest member of the cluster falls significantly behind other members of the cluster.
When a member of a cluster is slow at applying write-sets (while simultaneously […]

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How We Made Percona XtraDB Cluster Scale

wsrep-stages

In this blog post, we’ll look at the actions and efforts Percona experts took to scale Percona XtraDB Cluster.
Introduction
When we first started analyzing Percona XtraDB Cluster performance, it was pretty bad. We would see contention even with 16 threads. Performance was even worse with sync binlog=1, although the same pattern was observed even with the […]

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Galera Cache (gcache) is finally recoverable on restart

Gcache

This post describes how to recover Galera Cache (or gcache) on restart.
Recently Codership introduced (with Galera 3.19) a very important and long awaited feature. Now users can recover Galera cache on restart.
Need
If you gracefully shutdown cluster nodes one after another, with some lag time between nodes, then the last node to shutdown holds the latest […]

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Webinar Q/A: MySQL High Availability with Percona XtraDB Cluster 5.7

In this blog I will provide answers to the questions and queries that some of you have raised during the webinar on Nov 17th.
I would like to say thank you to all of the audience who attended the talk on November 17, 2016. You can also check the recording and slides here.
Q. How is storage […]

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All You Need to Know About GCache (Galera-Cache)

GCache

This blog discusses some important aspects of GCache.
Why do we need GCache?
Percona XtraDB Cluster is a multi-master topology, where a transaction executed on one node is replicated on another node(s) of the cluster. This transaction is then copied over from the group channel to Galera-Cache followed by apply action.
The cache can be discarded immediately once the […]

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How Percona XtraDB Cluster certification works

Percona XtraDB Cluster 5.7

In this blog, we’ll  discuss how Percona XtraDB Cluster certification works. Percona XtraDB Cluster replicates actions executed on one node to all other nodes in the cluster and make it fast enough to appear as it if is synchronous (aka virtually synchronous).

Let’s understand all the things involved in the process (without losing data integrity).

There are two […]

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