Even if a Galera node looks like a regular MySQL server, the underlying replication mechanism is very different. This implies some changes in the way you have to configure the Galera nodes. Here are some of the most common misconceptions about Galera when using Percona XtraDB Cluster.

Q: Why should I enable binary logging as it is not needed by Galera replication?
Unlike for regular asynchronous MySQL replication, it is true that you don’t need to enable binary logging to use Galera replication. However what if someone runs an accidental DROP TABLE?

In this case, the statement will be replicated immediately on all nodes. Then your main option to recover lost data is to use a backup. But if binary logging is not …

November 14, 2014 By Severalnines

Thanks to everyone who attended and participated in this week's webinar on '9 DevOps Tips for Going in Production with Galera Cluster for MySQL'. If you missed the sessions or would like to watch the webinar again & browse through the slides, they are now available online.

In this webinar, Severalnines CTO Johan Andersson discussed 9 key aspects to consider before taking Galera Cluster for MySQL into production:

• 101 Sanity Check
• Operating System
• Backup Strategies
• Galera Recovery
• Query Performance
• Schema changes
• Security / Encryption
• Reporting
• Protecting from Disasters

Watch the replay 9 DevOps Tips for Going in …

This blog post was inspired by my visit at the annual Zabbix Conference in Riga, Latvia this year, where I gave a couple of talks on MySQL and beyond.

It was a two day single-track event with some 200 participants, a number of interesting talks on Zabbix (and related technologies) and really well-organized evening activities. I was amazed how well organized the event was and hope to be invited to speak there next year as well.   (Just in case you’re not sure what Zabbix is, it is an enterprise-class open source distributed monitoring solution for networks and applications)

I must secretly confess, it was also the first conference …

From left: Liz van Dijk, Frédéric Descamps and Kenny Gryp

If you’re following this blog, it’s quite likely you’re already aware of the Percona Live London 2014 conference coming up in just a few days. Just in case, though (you know, if you’re still looking for an excuse to sign up), I wanted to put a spotlight on the tutorial to be delivered by my esteemed colleagues Frédéric Descamps (@lefred) and Kenny Gryp (@gryp), and …

I reckon there’s little sense in running 2 or more Percona XtraDB Cluster (PXC) nodes in a single physical server other than for educational and testing purposes – but doing so is still useful in those cases. The most popular way of achieving this seems to be with server virtualization, such as making use of Vagrant boxes. But in the same way you can have multiple instances of MySQL running in parallel on the OS level in the form of concurrent mysqld processes, so too can you have multiple Percona XtraDB Cluster nodes. And the way to achieve this is precisely the same: using dedicated datadirs and different ports for each node.

Which ports?4 tcp ports are used by Pecona …

Normally, when we want to start PXC (Percona XtraDB Cluster) on RHEL/CentOS 6 or older then that, we can simply start with init.d script or service command. i.e

shell> /etc/init.d/mysql start 
OR 
shell> /etc/init.d/mysql bootstrap-pxc

shell> service mysql start.

But, the way is changed from CentOS 7. Because systemd integration with RHEL/CentOS 7 is now available for Percona XtraDB Cluster (#1342223).

So now, we have to start mysql with systemctl command i.e

shell> systemctl start mysql

For boostrap,

shell> systemctl start mysql@bootstrap.service

I would also suggest to read one very informative post by Przemek for recovering PXC cluster. …

I was fortunate to attend an Ops discussion about databases at the OpenStack Summit Atlanta this past May as one of the panelists. The discussion was about deadlock issues OpenStack operators see with Percona XtraDB Cluster (of course this is applicable to any Galera-based solution). I asked to describe what they are seeing, and as it turned out, nova and neutron uses the SELECT … FOR UPDATE SQL construct quite heavily. This is a topic I thought was worth writing about.

Write set replication in a nutshell (with oversimplification)

Any node is writable, and replication happens in write sets. A write …

A common migration path from standalone MySQL/Percona Server to a Percona XtraDB Cluster (PXC) environment involves some measure of time where one node in the new cluster has been configured as a slave of the production master that the cluster is slated to replace. In this way, the new cluster acts as a slave of the production environment – traditional replication takes care of getting the data into the cluster, and then Galera replication handles the intra-cluster traffic. This often works without issue, although there is one case that I’ve encountered recently where special care must be taken to properly configure the stream to ensure that replication does not break. If you use multi-valued inserts with auto-increment columns, then this post is for you.

For purposes of our discussion, assume that we have a basic 3-node PXC cluster that we’ve set up …

When a write query is sent to Percona XtraDB Cluster all the nodes store the writeset on a file called gcache. By default the name of that file is galera.cache and it is stored in the MySQL datadir. This is a very important file, and as usual with the most important variables in MySQL, the default value is not good for high-loaded servers. Let’s see why it’s important and how can we calculate a correct value for the workload of our cluster.

What’s the gcache?
When a node goes out of the cluster (crash or maintenance) it obviously stops receiving changes. When you try to reconnect the node to the cluster the data will be outdated. The joiner node needs to ask a donor to send the changes happened during the downtime.

The donor …

Percona is glad to announce the new release of Percona XtraDB Cluster 5.5 on September 5th 2014. Binaries are available from downloads area or from our software repositories.

Based on Percona Server 5.5.39-36.0 including all the bug fixes in it, Galera Replicator 2.11, and on …