On Monday I will deliver with Seppo Jaakola from Codership a tutorial on Percona XtraDB Cluster (Percona Server + Galera).

Already in London and you don’t know how to consume the hotel’s bandwidth ? If you attend this tutorial, you can download the Virtual Box appliance we will use during the session.

Two versions are available:

• PLUK 2012 Appliance (32-bit)
• PLUK 2012 Appliance (64-bit)

How to test them:

1. Open the downloaded file with Virtual Box
2. Install all 3 machines
…

I learn more and more about Galera every day.  As I learn more, I try to keep my myq_gadgets toolkit up to date with what I consider is important to keep any eye on on a PXC node.  In that spirit, I just today pushed some changes to the ‘wsrep’ report, and I thought I’d go over some of the status variables and metrics being tracked there with the aim to show folks what they should be watching (at least from my opinion, this is subject to change!).

First, let’s take a look at the output:

[root@node3 ~]# myq_status -t 1 wsrep
Wsrep    Cluster        Node           Queue   Ops     Bytes     Flow        Conflct
    time  name P cnf  #  name  cmt sta  Up  Dn  Up  Dn   Up   Dn pau snt dst lcf bfa
19:17:01 trime P   3  3 node3 …

If you are interested by a great and revolutionary HA solution for MySQL or even if you already have some experience with PXC and/or Galera, I invite you to attend the tutorial I will deliver in Percona Live MySQL Conference London 2012 (PLUK2012), December 3rd : Percona XtraDB Cluster in a nutshell.

Small amount of theory and a lot of exercises and examples to really tame the beast that PXC is !

A Codership engineer will also be present and happy to help me answering your questions.

Note to attendees: please bring your laptop with a recent Virtual Box installed and enough free space to store 3 VMs (+/-2G per VM). As said …

I have addressed previously how multi-node writing causes unexpected deadlocks in PXC, at least, it is unexpected unless you know how Galera replication works.  This is a complicated topic and I personally feel like I’m only just starting to wrap my head around it.

The magic of Galera replication

The short of it is that Galera replication is not a doing a full 2-phase commit to replicate (where all nodes commit synchronously with the client), but it is instead something Codership calls “virtually synchronous” replication.  This could either be clever marketing or clever engineering, at least at face value.   However, I believe it really is clever engineering and that it is probably the best compromise for performance and data protection out there.

…

The Percona Toolkit team is happy to announce the release of Percona Toolkit version 2.1.6. This is the sixth stable release in the 2.1 series, and primarily a bug-fix release; We suggest that users upgrade to the latest version of the tools.

The complete list of changes is on the Launchpad milestone for 2.1.6, but here are some highlights the release:

• pt-online-schema-change can now handle column renames
• pt-online-schema-change’s DELETE trigger no longer fails when altering a primary key
• pt-stalk got a plugin hook interface
• pt-show-grant support for column-level grants
• pt-table-checksum will warn if slaves have a differing binlog_format

Remember that if you need help with Percona Toolkit, we provide flat-fee, unlimited support services with rapid 24×7 response on a …

Thanks for all, who attended my webinar, I got many questions and I wanted to take this opportunity to answer them.

Q: Even ntp has a delay of 0.3-0.4 between servers does that mean a 0.25 as from logs can be an issue ?
A: My demo vms were running for a few hours before the webinar in my local virtualbox instance, and I tried to show the minimal installation required for XtraDB cluster. Unfortunately enough, I didn’t include NTP, which caused SSTs to fail with the tar stream being from the future. The 0.3 – 0.4 second delay seems too much to me. According to the NTP standard, if the delay between the hosts is greater than 128 ms, NTP won’t work. So far for background and theory, from the practical point of view, you should have ntpd …

The Percona Toolkit team is happy to announce the release of Percona Toolkit version 2.1.4. This is the fifth stable release in the 2.1 series, and primarily a bug-fix release; We suggest that users upgrade to the latest version of the tools.

The complete list of changes is on the Launchpad milestone for 2.1.4, but here are some highlights the release:

• pt-table-checksum now works with Percona XtraDB Cluster
• The “Version Check” feature, explained at length here.
• –defaults-file is now used when connecting to discovered slaves in pt-table-checksum

All in all, a solid bug-fix release, with the addition of some new features too.

Remember that if you need …

I’ve mentioned this before, but I’m delivering a tutorial on Percona XtraDB Cluster / Galera at Percona Live NY 2012 right in midtown-Manhattan on October 1st.

I really want this tutorial to be hands-on, not just a 3 hour lecture, so you can actually see how a cluster operates and interact with it.  So, I have come up with a set of walkthroughs for different features and areas of learning PXC using a common set of Virtual Machines setup with Vagrant and Puppet (which works on Linux, OSX, or Windows).  This sounds complicated, but it basically means we can create a test environment with a full 3-node cluster on …

Some people want to use a backup to prepare a new Percona XtraDB Cluster node. They want this to avoid State Snapshot Transfer that could slow down the donor (depending of the SST method you are using, the donor can be blocked. I will cover this in a future blog post). As backup are generally performed during non-peak time, the effect should be reduced, and this avoid the need of performing 2 backups: the usual backup and the SST).

So to be able to use a backup for this purpose, we have 3 prerequisites:

• use XtraBackup >= 2.0.1
• the backup needs to be performed with –galera-info (option for innobackupex)
• have a gcache big enough to store all the changes from the time of the backup until the restore to be able to perform the Incremental State …

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 that kind of clusters, is to avoid split-brain situation. This can occur when quorum (that can be simplified as “majority vote”) is not honoured. A split-brain is a state in which the nodes lose contact with one another and then both try to take control of shared resources or provide simultaneously the cluster service.
On PRM the problem is obvious, both nodes will try to run the master and slave IPS and will accept writes. But what could happen with Galera replication on PXC ?

Ok first let’s have a look with a standard PXC setup (no special galera options), 2 nodes:

two running nodes (percona1 and percona2), communication between nodes is ok