[openstack-dev] [nova] Mysql db connection leaking?
jaypipes at gmail.com
Thu Apr 16 17:27:51 UTC 2015
On 04/16/2015 09:54 AM, Sean Dague wrote:
> On 04/16/2015 05:20 PM, Qiming Teng wrote:
>> Wondering if there is something misconfigured in my devstack
>> environment, which was reinstalled on RHEL7 about 10 days ago.
>> I'm often running into mysql connections problem as shown below:
>> $ mysql
>> ERROR 1040 (HY000): Too many connections
>> When I try dump the mysql connection list, I'm getting the followng
>> result after a 'systemctl restart mariadb.service':
>> $ mysqladmin processlist | grep nova | wc -l
>> Most of the connections are at Sleep status:
>> $ mysqladmin processlist | grep nova | grep Sleep | wc -l
>> As for the workload, I'm currently only running two VMs in a multi-host
>> devstack environment.
>> So, my questions:
>> - Why do we have so many mysql connections from nova?
>> - Is it possible this is caused some misconfigurations?
>> - 125 connections in such a toy setup is insane, any hints on nailing
>> down the connections to the responsible nova components?
> No, that's about right. It's 1 connection per worker. By default most
> daemons start 1 worker per processor. Each OpenStack service has a bunch
> of daemons. It all adds up pretty quick.
And just to add to what Sean says above, there's nothing inherently
wrong with sleeping connections to MySQL. What *is* wrong, however, is
that the default max_connections setting in my.cnf is 150. :( I
frequently recommend upping that to 2000 or more on any modern hardware
or decent sized VM.
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