Did your logging stop working after you set up logrotate? Then this post might be for you.

Archive your log files!

Some time ago, Peter Boros wrote about Rotating MySQL Slow Logs safely, explaining the steps of a “best practice” log rotate/archive. This post will add more info about the topic.

When running logrotate for MySQL (after proper setting the /etc/logrotate.d/mysql conf file) from anacron, there’s a situation that you might potentially face if the user and password used to execute the “flush logs” command is stored in, for example, /root/.my.cnf file.

The situation:

You might find out that you have a new MySQL log file ready to receive data, but nothing is being written to it.

Why did this happen?

The logrotate script is executed, but the postrotate …

If you need to automate backups, you might wonder about the different techniques available to you.

With regards to scheduling backups using built-in features of MySQL, you have two main options:

• Either run mysqldump (or mysqlbackup if you have an Enterprise licence) from an operating system scheduler, for example in Linux using "cron" or in Windows using the "Task Scheduler". This is the most commonly used option.
• Alternatively, use the Event Scheduler to perform a series of  SELECT ... INTO OUTFILE ... commands, one for each table you need to back up. This is a less commonly used option, but you might still find it useful.

Scheduling mysqlbackup with cron

mysqldump is a client program, so when you run it, you run it from a shell script, or at a terminal, rather than inside a MySQL statement. The following statement backs up the sakila …

When we analyze our customers systems we see typically a high fragmentation of the query cache after a while. This leads to a less optimal use of the Query Cache than possible.

With the following Query you can see the values for your Query Cache:

mysql> SHOW GLOBAL STATUS LIKE 'Qcache%';
+-------------------------+----------+
| Variable_name           | Value    |
+-------------------------+----------+
| Qcache_free_blocks      | 11328    |
| Qcache_free_memory      | 89442000 |
| Qcache_hits             | 6595644  |
| Qcache_inserts          | 1041831  |
| Qcache_lowmem_prunes    | 717896   |
| Qcache_not_cached       | 1040936  |
| Qcache_queries_in_cache | 17775    |
| Qcache_total_blocks     | 46990    |
+-------------------------+----------+

Watch out for the value of Qcache_free_blocks and Qcache_free_memory.

The MySQL documentation states: You can defragment the …