The behaviour changed in 5.6.12. For more details see this bug report (which I consider fixed):
http://bugs.mysql.com/bug.php?id=62224

There is also a small patch attached to that bug which changes the behaviour and sets the limit to the hard limit instead of the soft limit if setting the requested limit fails.

And for troubleshooting something like this should be used instead the more classical ‘switch to the user and do a ulimit -a’. With cgroups in linux the limit for the mysql user and the mysql process might be different.
egrep ‘^(Limit|Max open files)’ /proc/`pidof mysqld`/limits

And this one is also a classic:
http://www.mysqlperformanceblog.com/2013/02/04/cant_create_thread_errno_11/

MySQL variables open_files_limit, table_open_cache and max_connections are
inter-related, and this is for obvious reasons: all deal with file descriptors
one way or another.

If one of the value is provided but others are left out, mysqld calculates
others using a formula and in some cases, emits a warning if not possible.

The whole calculation behind obtaining the final file descriptor limit is a bit
byzantine and is as follows (for Linux):

EDIT: This applies to MySQL 5.5, in 5.6, as Daniël in comments pointed out,
few things have changed, check comment for details. I will probably make a
followup post on the differences.

1. First it tries to calculate a minimum requirement based on max_connections …

Via Dave Stokes, MySQL Community Manager:

MySQL Central is truly a MySQL Community show. This year there are five tracks and the majority of the sessions in all the tracks except Performance and Scalability had many more submissions from the MySQL Community than from Oracle/MySQL.

This is impressive. There are about 200 submissions, 50 slots, a 1/4 chance of a talk getting in, and if we follow this logic we will see that MySQL Central @ OpenWorld will truly be a community event (in previous years, majority of the talks came from the MySQL team at Oracle). I can’t wait to see the final program, but as an attendee to the past two MySQL Connect events, I am looking forward to seeing this event grow and be a part of the main program (i.e. not the weekend before).

As …

So benchmarking different MySQL queries against your database is a wise thing to do. That should go without saying. While we optimize queries the best we can using EXPLAIN (and EXPLAIN EXTENDED)  taking them time to benchmark them should prove helpful.

This is a simple example of executing a mysqlslap statement.

For this example I loaded the WORLD database from MySQL. ( http://dev.mysql.com/doc/index-other.html )

I created a query that joined all three tables  and put it into /tmp/tests.sql. The explain plan is below.

root@localhost [world]> EXPLAIN EXTENDED SELECT C.Name as City, Y.Name as Country, L.Language,Y.Population FROM City C INNER JOIN Country Y ON C.CountryCode = Y.Code INNER JOIN CountryLanguage L ON C.CountryCode = L.CountryCode WHERE C.Name LIKE 'D%' AND Y.Continent='Europe' \G
…

Это первая статья из серии, посвященной сравнению iOS и Android. Вообще говоря, это написано скорее больше для себя, чтобы отметить наиболее интересные моменты и чтобы привести мысли в порядок. Когда пользуешься определённым девайсом со временем привыкаешь к его сильным сторонам, начинаешь их считать обыкновенными, а неудобство от слабых черт доставляет недовольство и сподвигает и искать что-то новое. Так вот, текст для того, чтобы помнить... :)

Основным оппонентом будет Samsung Note 2, т.к. он был у меня непосредственно перед iPhone 5S, и …

MySQL Central is truly a MySQL Community show. This year there are five tracks and the majority of the sessions in all the tracks except Performance and Scalability had many more submissions from the MySQL Community than from Oracle/MySQL. The voting has been tough this year for me. Picking roughly fifty talks out of about two hundred submissions may sound easy. But this year I found only a few topics that were easy to score lowly as they were either off the mark for the conference or not strong enough subjects for the devotion of an hour. So that took it down from two hundred sessions to one ninety seven.

I do not know how the other selectors are making their choices but I had an exhausting time of it. The first pass took me a week part-time to read all the details of each submission without looking at the author in order to judge the talks on their content. Next I look for amazing presenters who have taught me something in the …

While at the keynote of Tomas Ulin at Percona Live MySQL Conference & Expo Santa Clara 2014, he asked the audience what they were running, and most of the audience was on MySQL 5.5 while about 15% of the audience was on MySQL 5.6. This number is steadily increasing I’m sure, so one thing that becomes important is that people will probably start turning on Global Transaction Identifiers (GTIDs). 

As you may already know, MariaDB 10 has a different implementation of Global Transaction ID. To me, this poses a problem in a mixed use environment (or even a migration scenario). Which is why …

There are many MySQL related IRC discussion channels as the ecosystem itself grows. I join the following. Are there any that I’m missing?

Freenode (irc.freenode.net):

• #mysql – main channel for all kinds of end user MySQL related discussions (the noisiest of the lot, naturally)
• #maria – main channel for all kinds of MariaDB related discussions
• #webscalesql – for all kinds of WebScaleSQL discussions
• #percona – main channel for all kinds of Percona related discussions
• #tokutek – main channel for Tokutek discussions (TokuDB or TokuMX)
• SkySQL-specific channels: #maxscale and #mariadb-mgr

OFTC (irc.oftc.net):

• #debian-mysql – for all kinds of Debian MySQL related bits (packaging, bugs, etc.)

Related posts:

1. …

Oracle OpenWorld, taking place Sept 28-Oct 2, 2014 in San Francisco, is the world’s largest gathering of technology and business professionals. The conference includes several dedicated programs focused on specific technologies and solutions, such as Human Capital Management, Customer Experience, and MySQL.

In order to bring more consistency, clarity and visibility to those programs, they have all been renamed "Central". MySQL Connect therefore becomes "MySQL Central @ OpenWorld", and we will use this name moving forward.

MySQL Central @ OpenWorld offers you the opportunity to hear directly from Oracle’s MySQL engineers about the latest MySQL features, enhancements and plans. Best Practices sessions by MySQL customers, community members and partners will help you understand how to make the most of MySQL.

MySQL Central @ OpenWorld includes:

Here on the Percona MySQL Support team, we often see issues where a customer is complaining about replication delays – and many times the problem ends up being tied to MySQL replication slave lag. This of course is nothing new for MySQL users and we’ve had a few posts here on the MySQL Performance Blog on this topic over the years (two particularly popular post in the past were: “Reasons for MySQL Replication Lag” and “Managing Slave Lag with MySQL Replication,” both by Percona CEO Peter Zaitsev).

In …