Galera data on Percona Cloud Tools (and other MySQL monitoring tools)

I was talking with a Percona Support customer earlier this week who was looking for Galera data on Percona Cloud Tools. (Percona Cloud Tools, now in free beta, is a hosted service providing access to query performance insights for all MySQL uses.)

The customer mentioned they were already keeping track of some Galera stats on Cacti, and given they were inclined to use Percona Cloud Tools more and more, they wanted to know if it was already supporting Percona XtraDB Cluster. My answer was: “No, not yet: you can install agents in each node (the regular way in the first node, then manually on the other nodes… and when prompted say “No” to create MySQL user and provide the one you’re using already) and monitor them as autonomous MySQL servers – but the concept of cluster and specially the “Galera bits” has yet to be implemented there.

Except I was wrong.

By “concept of cluster” I mean supporting the notion of group instances, which should allow a single cluster-wide view for metrics and query reports, such as the slow queries (which are recorded locally on the node where the query was run and thus observed in a detached way). This still needs to be implemented indeed, but it’s on the roadmap.

The “Galera bits” I mentioned above are the various “wsrep_” status variables. In fact, those refer to the Write Set REPlication patches (based in the wsrep API), a set of hooks applied to the InnoDB/XtraDB storage engine and other components of MySQL that modifies the way replication works (to put it in a very simplified way), which in turn are used by the Galera library to provide a “generic Synchronous Multi-Master replication plugin for transactional applications.” A patched version of Percona Server together with the Galera libray compose the base of Percona XtraDB Cluster.

As I found out only now, Percona Cloud Tools does collect data from the various wsrep_ variables and it is available for use – it’s just not shown by default. A user only needs to add a dashboard/chart manually on PCT to see these metrics:


Click on the picture to enlarge it

Now, I need to call that customer …

Monitoring the cluster

Since I’m touching this topic I thought it would be useful to include some additional information on monitoring a Galera (Percona XtraDB Cluster in particular) cluster, even though most of what I mention below has already been published in different posts here on the MySQL Performance Blog. There’s a succint documentation page bearing the same title of this section that indicates the main wsrep_ variables you should monitor to check the health status of the cluster and how well it’s coping with load along the time (performance). Remember you can get a grasp of the full set of variables at any time by issuing the following command from one (or each one) of the nodes:

mysql> SHOW GLOBAL STATUS LIKE "wsrep_%";

And for a broader and real time view of the wsrep_ status variables you can use Jay Janssen’s myq_gadgets toolkit, which he modified a couple of years ago to account for Galera.

There’s also a specific Galera-template available in our Percona Monitoring Plugins (PMP) package that you can use in your Cacti server. That would cover the “how well the cluster copes with load along the time,” providing historical graphing. And while there isn’t a Galera specific plugin for Nagios in PMP, Jay explains in another post how you can customize pmp-check-mysql-status to “check any status variable you like,” describing his approach to keep a cluster’s “health status” in check by setting alerts on specific stats, on a per node basis.

VividCortex recently added a set of templates for Galera in their product and you can also rely on Severalnines’ ClusterControl monitoring features to get that “global view” of your cluster that Percona Cloud Tools doesn’t yet provide. Even though ClusterControl is a complete solution for cluster deployment and management, focusing on the automation of the whole process, the monitoring part alone is particularly interesting as it encompasses cluster-wide information in a customized way, including the “Galera bits”. You may want to give it a try as the monitoring features are available in the Community version of the product (and if you’re a Percona customer with a Support contract covering Percona XtraDB Cluster, then you’re entitled to get support for it from us).

One thing I should note that differentiate the monitoring solutions from above is that while you can install Cacti, Nagios and ClusterControl as servers in your own infrastructure both Percona Cloud Tools and VividCortex are hosted, cloud-based services. Having said that, neither one nor the other upload sensitive data to the cloud and both provide options for query obfuscation.


Contrary to what I believed, Percona Cloud Tools does provide support for “Galera bits” (the wsrep_ status variables), even though it has yet to implement support for the notion of group instances, which will allow for cluster-wide view for metrics and query reports. You can also rely on the Galera template for Cacti provided by Percona Monitoring Plugins for historical graphing and some clever use of Nagios’ pmp-check-mysql-status for customized cluster alerts. VividCortex and ClusterControl also provide monitoring for Galera.

Percona Cloud Tools, now in free beta, is a hosted service providing access to query performance insights for all MySQL uses. After a brief setup, unlock new information about your database and how to improve your applications. Sign up to request access to the beta today.  

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How to setup Docker for Percona ClusterControl and add existing Percona XtraDB Cluster

In my previous post I showed you how to setup Percona XtraDB Cluster 5.6 on Docker. This time I will show you how to setup Percona ClusterControl and add the existing Percona XtraDB Cluster 5.6 that we’ve managed to setup from the previous post.

Let us note the following details about our existing containers:

  • dockerpxc1
  • dockerpxc2
  • dockerpxc3
  • dockerccui-test

A quick tip for everyone who has followed my previous blog on setting up Percona XtraDB Cluster 5.6 on Docker: I did not install OpenSSH on the Docker instances on purpose and relied on ‘docker attach’ command to be able to get into each container. For this case however, we will need to install openssh-server in each container and make sure SSH is running as well as setup SSH key access for the Percona ClusterControl container to SSH into each Percona XtraDB Cluster node.

Create the Percona ClusterControl UI Docker container

We will need to create a docker container manually instead of building a container from a Dockerfile since we can’t run the ClusterControl installation non-interactively.

root@Perconallc-Support / # docker run --name dockerccui-test -p 80 -i -t ubuntu:12.04 bash

Notice that I had to add ‘-p 80′ to expose port 80 to the host network so we can access the Percona ClusterControl UI from a web browser, we will use Ubuntu 12.04 docker image. I will show you how to check the port that was dynamically allocated on the host network.

I would recommend to run ‘apt-get upgrade’ and ‘apt-get dist-upgrade’ just to make sure we have the latest software packages installed. Install wget and lsb-release packages since these are needed in the next steps.

Download and run the Percona ClusterControl installer and follow instructions on the prompt.

root@Perconallc-Support / # chmod +x
root@Perconallc-Support / # ./

The installer will give you several options, one of which is to install Percona Server as Percona ClusterControl’s backend database, I’d highly recommend to choose ‘Yes’. If everything goes well you will need to continue setup of the Percona ClusterControl on the web browser. If you missed installing lsb-release earlier then you will get an error midway through the installation, but you can always install lsb-release package and re-run the installation.

To identify the exposed port on the host’s side we will need to verify it:

root@Perconallc-Support / # docker inspect dockerccui-test | grep HostPort
                    "HostPort": "49154"
                    "HostPort": "49154"

As we can see, port 49154 was dynamically allocated to the host network and mapped to port 80 on the docker instance. You may explicitly set the port mapping on the host network ‘-p {hostPort}:{containerPort}’, please consult official Docker documentation for further reading.

Setup Percona ClusterControl on the web browser

We can now access the Percona ClusterControl user interface through http://{Host}:49154/clustercontrol. Use the username (in email form) that you indicated during the installation and the default password ‘admin’ to log in.

We should see the following page after successfully logging in:

Percona ClusterControl

Percona ClusterControl Wizard

Select ‘Add an existing cluster’ and click Next then follow further instructions to get to the next page:

add existing cluster

Add existing cluster

If all goes well you will be seeing the Database Clusters and can view your cluster nodes.

Percona ClusterControl

Percona ClusterControl UI on Docker container with Percona XtraDB Clusters 5.6 with each node on docker containers


In this blog I showed you how to setup Percona ClusterControl on Docker and adding an existing cluster to ClusterControl.

* Create a Docker container for Percona ClusterControl
* Download Percona ClusterControl and installed it
* Added existing Percona XtraDB Cluster on the Percona ClusterControl UI
* Profit!

You may also read the following blogs related to Percona ClusterControl:

For those who are new to Docker and containerization you may read through Patrick Galbraith’s blog series about Docker.

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