Docker is quickly becoming mainstream, as a method to package and deploy self-sufficient applications in primarily stateless Linux containers. But for a stateful service like a database, this might be bit of a headache. How do we best configure MySQL in a container environment? What can go wrong? Should we even run our databases in a container environment? How does performance compare with e.g. running on virtual machines or bare-metal servers? How do we manage replicated or clustered setups, where multiple containers need to be created, upgraded and made highly available?

So, welcome to our new blog series - “MySQL on Docker”. We will touch upon swarms, shared volumes, data-only-containers, security and configuration management, multi-host networking, service discovery and implications on monitoring when we move from host-centric to role-centric services with shorter life cycles.

In our first blog post, we are going to cover …

Percona is glad to announce the GA release of Percona Server 5.7.12-5 on June 6, 2016. Download the latest version from the Percona web site or from the Percona Software Repositories.

Based on MySQL 5.7.12, including all the bug fixes in it, Percona Server 5.7.12-5 is the current GA release in the Percona Server 5.7 series. All of Percona’s software is open-source and free, all the details of the release can be found in the …

We have had to revert back to TLSv1.0.

If you saw my previous post on TLSv1.0 (https://www.percona.com/blog/2016/05/23/percona-disabling-tlsv1-0-may-31st-2016/), you’ll know I  wanted to deprecate TLSv1.0 well ahead of PCI’s changes. We made the changes May 31st.

Unfortunately, it has become apparent that EL 5, which is in the final phases of End Of Life, does not support TLSv1.1 or TLSv1.2. As such, I have had to re-enable TLSv1.0 support so that these users employing EL 5 can still receive updates from our repositories.

If you are running EL 5 (RHEL 5 / CentOS 5 / Scientific Linux 5 / etc …), I …

In this blog, I discuss a MongoDB administration checklist designed to help MySQL DBAs.

If you are MySQL DBA, starting MongoDB administration is not always an easy transition. Although most of the concepts and even implementation are similar, the commands are different. The following table outlines the typical MySQL concepts and DBA tasks (on the left) to corresponding MongoDB ones (on the right). If you happen to be a MongoDB DBA and want to learn MySQL administration, you can use the same table looking from right to left.

I’ve also created a webinar, MongoDB administration for MySQL DBA, that explains the above concepts. You can download the slides to use as a reference.

Don’t forget …

In this blog, I will provide answers to the Q & A for the Troubleshooting locking issues webinar.

First, I want to thank you for attending the May, 12 webinar. The recording and slides for the webinar are available here. Below is the list of your questions that I wasn’t able to answer during the webinar, with responses:

Q: Do you have the links to those other info sources?

A: Yes, they are listed in the “More Information” slide. In the PDF, all the links are active. If you speak Russian, you can also check …

New versions of systemd (like in Ubuntu 16.04) are able to configure pid Cgroups (ulimit -u via Cgroups) using TasksMax.

Check the commit implementing TaksMax.

Author: Lennart Poettering <lennart@poettering.net>
Date:   Fri Nov 13 19:28:32 2015 +0100

    core: enable TasksMax= for all services by default, and set it to 512

    Also, enable TasksAccounting= for all services by default, too.

    See:

    http://lists.freedesktop.org/archives/systemd-devel/2015-November/035006.html

But not we’ve got silly defaults:

$ systemctl show -p TasksMax docker
TasksMax=512

$ systemctl show -p TasksMax mysql
TasksMax=512

So if you use Docker or MySQL most likely you are going to have trouble without really putting load on your server.

Just set TasksMax for your service.

TasksMax=infinity

Feel free to configure that setting fitting …

I was speaking at PHP[Tek] this week on the JSON Data Type and using generated columns. JSON columns can not be indexed but data from a JSON column can be extracted via a generated column and that column can be indexed. All was going well until someone asked me about modifying data in a generated column. Was it possible?

I blinked hard. I have not tried that! I had not seen any mention of that in the documentation. So I had to admit that I did not know and would have to try that.

The Test

mysql> CREATE TABLE gentest (a INT, b INT AS (a + 1) STORED, INDEX(b));
...
mysql> INSERT INTO gentest VALUES (1),(2),(3),(4);
...

So now we have a table with data to test. So lets try to modify the value of one of the generated columns.

mysql> UPDATE gentest SET b = 9 WHERE a = 1;

And what did …

Percona is glad to announce the release of Percona Server 5.6.30-76.3 on May 25, 2016. Download the latest version from the Percona web site or the Percona Software Repositories.

Based on MySQL 5.6.30, including all the bug fixes in it, Percona Server 5.6.30-76.3 is the current GA release in the Percona Server 5.6 series. Percona Server is open-source and free …

A customer reported last month that MySQL does a full table scan (FTS) if a query was filtered by a INT value on a VARCHAR column. First I told him that this is not true any more because MySQL has fixed this behaviour long time ago. He showed me that I was wrong:

CREATE TABLE `test` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `data` varchar(64) DEFAULT NULL,
  `ts` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  PRIMARY KEY (`id`),
  KEY `data` (`data`)
) ENGINE=InnoDB;

EXPLAIN SELECT * FROM test WHERE data = 42\G
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: test
   partitions: NULL
         type: ALL
possible_keys: data
          key: NULL
      key_len: NULL
          ref: NULL
         rows: 522500
     filtered: 10.00
        Extra: Using where

EXPLAIN SELECT * FROM test WHERE data = …

In this blog post we’ll discuss pt-online-schema-change, and how to correctly use it.

Always use pt-osc?

Altering large tables can be still a problematic DBA task, even now after we’ve improved Online DDL features in MySQL 5.6 and 5.7. Some ALTER types are still not online, or sometimes just too expensive to execute on busy production master.

So in some cases, we may want to apply an

ALTER

 first on slaves, taking them out of traffic pool one by one and bringing them back after the

ALTER

 is done. In the end, we can promote one of the already altered slaves to be new master, so that the downtime/maintenance time is greatly minimized. The ex-master can be altered later, without affecting production. Of course, this method works best when the schema change is …