On 4/16/2015 12:27 PM, Jay Pipes wrote:
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
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What do you consider a decent sized VM? In devstack we default
max_connections for postgresql to 200 because we were having connection
timeout failures in the gate for pg back in the day:
http://git.openstack.org/cgit/openstack-dev/devstack/tree/lib/databases/postgresql#n15
But we don't change this for mysql:
http://git.openstack.org/cgit/openstack-dev/devstack/tree/lib/databases/mysql
I think the VMs in the gate are running 8 VCPU + 8 GB RAM, not sure
about disk.
--
Thanks,
Matt Riedemann
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