The latest from the MySQL community

To only slightly misquote one of the greatest movies of all times:

You keep using that option.  I do not think it means what you think it means.

Perhaps like many users, I had certain assumptions about what max_connect_errors really does – but in looking closely as part of investigating the new PERFORMANCE_SCHEMA.HOST_CACHE table in MySQL 5.6, I learned that some very fundamental elements had escaped my notice.  I’m writing this blog post to help others who hold similar misconceptions of what this option does.

Many, if not most, MySQL DBAs are familiar with “host blocked” errors:

C:\mysql-5.5.27-winx64>bin\mysql -utest_mce -P3307 -h192.168.2.8
ERROR 1129 (HY000): Host …

Good news everyone! I recently presented a webinar: Percona Server 5.6: Enterprise Grade MySQL. It was also recorded so you can watch along or view the slide deck. As with all my talks, I am not simply reading the slides so it really is worth to listen to the audio rather than just glance through the slide deck.

There were a number of great questions asked which I’ll answer below:

Q: How does Stewart feel about this version of 5.6 taking into consideration “Stewart’s .20 rule?” (ref 2013 Percona Live Conference).

A: For those who aren’t familiar with it, I have a rule which I call “Stewart’s dot twenty rule” which I’ve posted a few times about on my personal blog. It …

In an earlier post, I commented on clients and utility programs which seem to no longer be useful, and opened (or referenced existing) public bug reports to deprecate and remove, where appropriate.  That effort came actually was the product of a different initiative:  I was looking for clients which might leverage the full spectrum of MySQL protocol commands in an effort to understand whether certain protocol commands are in use.  I thought I would share my observations, in the hope that we might also get feedback from others regarding usage of these commands. And even though it’s no longer spring (I started this post in April), I finally found time to finish this post.

The first group to mention are those which are …

Over three years ago, I noticed that there was no STATUS counter for COM_PING commands – something that is useful for ensuring proper configuration of JDBC connection pools.  Mark Leith even provided a patch, but it’s never been incorporated.  With the advances PERFORMANCE_SCHEMA makes in MySQL 5.6, that’s OK – a STATUS counter becomes somewhat redundant:

mysql> SELECT SUM(count_star) as pings
    -> FROM events_statements_summary_global_by_event_name
    -> WHERE event_name = 'statement/com/Ping';
+-------+
| pings |
+-------+
|    12 |
+-------+
1 row in set (0.02 sec)

Not only does PERFORMANCE_SCHEMA provide capabilities which mirror the STATUS counters, it really goes well beyond what’s capable there. A global counter is interesting, but …

With the release of MySQL Utilities 1.3.4, the standalone (not bundled with the MySQL WorkBench GUI) package is now Generally Available and fully supported. This post will focus on a very important change (the ability to run as a daemon rather than in a terminal) to the mysqlfailover utility which allows you to build a light-weight HA database solution using MySQL Replication.

For a general overview of MySQL Utilities, take a look at this recent webinar or for a deeper dive into using them to setup replication and adding auto-failover of the master function to slaves watch this video and worked example. …

MySQL 5.6.13 was released earlier this week, and in that release (as well as 5.5.33) the ability to use unique option prefixes was deprecated.  This is fully removed from MySQL 5.7, and I thought it might be useful to amplify the change log notes on why this was done:

Previously, program options could be specified in full or as any unambiguous prefix. For example, the --compress option could be given to mysqldump as --compr, but not as --comp because the latter is ambiguous. Option prefixes now are deprecated. They can cause problems when new options are implemented for programs. A prefix that is …

Idle connections can cause problems both at the application side, increasing the risk of connection timeouts for applications where persistent connections are used, and the server side, where resources remain allocated to idle connections.  Any application with persistent connections, such as a JDBC application using a connection pool, will have periods where connections are idle – but it’s good to know how much time is spent idle.  Too much idle time might mean connections pools configured to allow too many connections to sit idle in a connection pool, or not properly doing connection pool maintenance.

PERFORMANCE_SCHEMA in MySQL 5.6 makes it trivial to measure absolute time spent waiting.  This will show total, average and maximum idle times by account:

mysql> SELECT …

I’ve often wished that PROCESSLIST exposed when a connection was first established, and I find myself wishing for this information more now with MySQL 5.6.  Improvements to PERFORMANCE_SCHEMA make it trivial to see how much time is being spent in various operations for a given connection – but it would make some analysis (“what percentage of connection time is spent doing X?”) easier.

That said, it is possible to approximate connection age with PERFORMANCE_SCHEMA in MySQL 5.6.  I say “approximate” because results will vary based on what instrumentation exists, is enabled, and is collecting timing data.  That’s because we’re just doing a SUM() on the SUM_TIMER_WAIT column for all instrumented waits.  Here’s an example (FYI, I’m using the format_time() function from Mark Leith’s …

This is part 3 of a 3 part series covering the new InnoDB full-text search features in MySQL 5.6. To catch up on the previous parts, see part 1 or part 2

Some of you may recall a few months ago that I promised a third part in my InnoDB full-text search (FTS) series, in which I’d actually take a look at the performance of InnoDB FTS in MySQL 5.6 versus traditional MyISAM FTS. I hadn’t planned on quite such a gap between part 2 and part 3, but as they say, better late than never. Recall that we have been working with two data sets, one which I call SEO (8000-keyword-stuffed web pages) and the other which I call DIR (800K directory records), and we are comparing MyISAM FTS in …

In a previous post, I described how to leverage PERFORMANCE_SCHEMA in MySQL 5.6 to identify connections which had not been properly closed by the client.  One possible cause of connections being closed without explicit request from the client is when another process issues a KILL CONNECTION command:

mysql> SHOW GLOBAL STATUS LIKE 'aborted_clients';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| Aborted_clients | 0     |
+-----------------+-------+
1 row in set (0.02 sec)

mysql> KILL CONNECTION 3;
Query OK, 0 rows affected (0.00 sec)

mysql> SHOW GLOBAL STATUS LIKE 'aborted_clients';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| Aborted_clients | 1     |
+-----------------+-------+
1 row in set (0.00 sec)

You …