Open Stack

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
>> 125
>>
>> Most of the connections are at Sleep status:
>>
>> $ mysqladmin processlist | grep nova | grep Sleep | wc -l
>> 123
>>
>> 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?
>>
>> Thanks.
>>
>> Regards,
>>    Qiming
>
> 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.

Best,
-jay