I’ve been blogging a lot about some of the new things you can expect with Percona XtraDB Cluster 5.6 and Galera 3.x – and GA is coming …

Most technologies achieving high-availability for MySQL need a load-balancer to spread the client connections to a valid database host, even the Tungsten special connector can be seen as a sophisticated load-balancer. People often use hardware load balancer or software solution like haproxy. In both cases, in order to avoid having a single point of failure, multiple load balancers must be used. Load balancers have two drawbacks: they increase network latency and/or they add a validation check load on the database servers. The increased network latency is obvious in the case of standalone load balancers where you must first connect to the load balancer which then completes the request by connecting to one of the database servers. Some workloads like reporting/adhoc queries are not affected by a small increase of latency but other workloads like oltp processing and real-time logging are. Each load balancers must also check regularly if the database …

Gcache and IST

The Gcache is a memory-based cache of recent Galera transactions that is local to each node in a cluster.  If a node leaves and rejoins the cluster, it can use the gcache from another node that stayed in the cluster (i.e., its donor node) to fetch the transactions it missed (IST) as opposed to doing a full state snapshot transfer (SST).  However, there are a few nuances that are not obvious to the beginner:

• The Gcache is lost when a node restarts
• The Gcache is fixed size and implemented as a LRU.  Once it is full, older transactions roll off.
• Donor selection is made irregardless of the gcache state
• If the given donor for a restarting node doesn’t have all transactions needed, a full SST (read: full backup) is done instead
• Until recent developments, there was no way to tell what, precisely, was in the Gcache.

So, with (somewhat) …

A decade ago MySQL folks were in love with the concept of a relay slave for MySQL high availability across data centers.  A relay is a single slave in a remote data center that receives replication from the global master and, in turn, replicates to all the other local slaves in that data center.  This saved a lot of bandwidth, especially back in the days before memcached when scaling reads meant lots of slaves.  Sending 20 copies of your replication stream cross-WAN gets expensive.

In Galera and Percona XtraDB Cluster (PXC), by default when a transaction commits on a given node it is sent to every other node in the cluster from that node.  That is, the actual writeset payload (the RBR events) are sent over the network to every other node, so the bandwidth to replicate is roughly:

<writeset size> * …

Percona is glad to announce the release of Percona XtraDB Cluster 5.5.34-25.9 on December 4, 2013. Binaries are available from the downloads area or from our software repositories.

Based on Percona Server 5.5.34-32.0 including all the bug fixes in it, Galera Replicator and on Codership wsrep API 5.5.34-25.9, Percona XtraDB Cluster …

I get a lot of questions about Percona XtraDB Cluster 5.6 (PXC 5.6), specifically about whether such and such MySQL 5.6 Community Edition feature is in PXC 5.6.  The short answer is: yes, all features in community MySQL 5.6 are in Percona Server 5.6 and, in turn, are in PXC 5.6.  Whether or not the new feature is useful in 5.6 really depends on how useful it is in general with Galera.

I thought it would be useful to highlight a few features and try to show them working:

Innodb Fulltext Indexes

Yes, FTS works in Innodb in 5.6, so why wouldn’t it work in PXC 5.6?  To test this I used the Sakila database , which contains a single table with FULLTEXT.  In the sakila-schema.sql file, it is still designated a MyISAM table:

Now that Percona XtraDB Cluster 5.6 is out in beta, I wanted to start a series talking about new features in Galera 3 and PXC 5.6.  On the surface, Galera 3 doesn’t reveal a lot of new features yet, but there has been a lot of refactoring of the system in preparation for great new features in the future.

Galera vs MySQL options

wsrep_provider_options is a semi-colon separated list of key => value configurations that set low-level Galera library configuration.  These tweak the actual cluster communication and replication in the group communication system.  By contrast, other PXC global variables (like ‘wsrep%’) are set like other mysqld options and generally have more to do with MySQL/Galera …

Percona is glad to announce the first Beta release of Percona XtraDB Cluster 5.6 on November 21st, 2013. Binaries are available from downloads area or from our software repositories.

Based on Percona Server 5.6.14-62.0 including all the bug fixes in it, Galera Replicator 3.1 and on Codership wsrep API 5.6.14-25.1 is …

It is a rather frequent problem to have to manage Virtual IP addresses (VIPs) with a Percona XtraDB Cluster (PXC) or with MySQL master HA (MHA). In order to help solving these problems, I wrote a Pacemaker agent, mysql_monitor that is a simplified version of the mysql_prm agent. The mysql_monitor agent only monitors MySQL and set attributes according to the state of MySQL, the read-only variable, the slave status and/or the output of the clustercheck script for PXC. The agent can operate in 3 modes or cluster types: replication (default), pxc and read-only.

The simplest mode is read-only, only the state of the read_only variable is looked at. If the node has the read_only variable set to OFF, then the writer is set to 1 and reader attributes is set to 1 while if the node has read_only set to ON, the writer attributes will …

The Percona Monitoring Plugins (PMP) provide some free tools to make it easier to monitor PXC/Galera nodes.  Monitoring broadly falls into two categories: alerting and historical graphing, and the plugins support Nagios and Cacti, respectively, for those purposes.

Graphing

An update to the PMP this summer (thanks to our Remote DBA team for supporting this!) added a Galera-specific host template that includes a variety of Galera-related stats, including:

• Replication …