September 18, 2014

Prevent MySQL downtime: Set max_user_connections

One of the common causes of downtime with MySQL is running out of connections. Have you ever seen this error? “ERROR 1040 (00000): Too many connections.” If you’re working with MySQL long enough you surely have. This is quite a nasty error as it might cause complete downtime… transient errors with successful transactions mixed with […]

MySQL Error: Too many connections

We have always received quite few questions here at Percona Support on how to avoid the dreaded “Too many connections” error, as well as what is the recommended value for max_connections. So, in this article I will try to cover best possible answers to these questions so others can mitigate similar kinds of issues. My […]

Filling the tmp partition with persistent connections

The use of tmpfs/ramfs as /tmp partition is a common trick to improve the performance of on-disk temporary tables. Servers usually have less RAM than disk space so those kind of partitions are very limited in size and there are some cases were we can run out of space. Let’s see one example. We’re running […]

Configuring MySQL For High Number of Connections per Second

One thing I noticed during the observation was that there were roughly 2,000 new connections to MySQL per second during peak times. This is a high number by any account. When a new connection to MySQL is made, it can go into the back_log, which effectively serves as a queue for new connections on operating […]

Impact of the number of idle connections in MySQL

Be careful with my findings, I appear to have compile in debug mode, I am redoing the benchmarks. Updated version here. I recently had to work with many customers having large number of connections opened in MySQL and although I told them this was not optimal, I had no solid arguments to present. More than […]

Too many connections? No problem!

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Are PHP persistent connections evil ?

As you probably know PHP “mysql” extension supported persistent connections but they were disabled in new “mysqli” extension, which is probably one of the reasons some people delay migration to this extension. The reason behind using persistent connections is of course reducing number of connects which are rather expensive, even though they are much faster […]

Review of MySQL 5.6 Defaults Changes

James Day just posted the great summary of defaults changes in MySQL 5.6 compared to MySQL 5.5 In general there are a lot of good changes and many defaults are now computed instead of hardcoded. Though some of changes are rather puzzling for me. Lets go over them: back_log = 50 + ( max_connections / […]

Percona XtraDB Cluster 5.5.39-25.11 is now available

Percona is glad to announce the new release of Percona XtraDB Cluster 5.5 on September 5th 2014. Binaries are available from downloads area or from our software repositories. Based on Percona Server 5.5.39-36.0 including all the bug fixes in it, Galera Replicator 2.11, and on Codership wsrep API 25.11, Percona XtraDB Cluster 5.5.39-25.11 is now […]

Percona XtraDB Cluster 5.6.20-25.7 is now available

Percona is glad to announce the new release of Percona XtraDB Cluster 5.6 on September 1st 2014. Binaries are available from downloads area or from our software repositories. Based on Percona Server 5.6.20-68.0 including all the bug fixes in it, Galera Replicator 3.7, and on Codership wsrep API 25.7, Percona XtraDB Cluster 5.6.20-25.7 is now […]