Excerpts from Matt Riedemann's message of 2015-04-16 15:40:30 -0700: > > 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 > > > > __________________________________________________________________________ > > OpenStack Development Mailing List (not for usage questions) > > Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe > > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev > > > > 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. >
Note that pgsql's connection model is vastly different than mysql's. For mysql, each connection doing nothing uses very little RAM. For pgsql, IIRC, each one is a forked process. __________________________________________________________________________ OpenStack Development Mailing List (not for usage questions) Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev