On 6/18/15 3:53 PM, Sean Dague wrote:
On 06/18/2015 03:47 PM, Mike Bayer wrote:
On 6/18/15 1:28 PM, Matt Riedemann wrote:
It's not only neutron, I saw some pymysql failures in nova the other
day for 'too many connections' or some such related error.
"too many connections" is an error raised by MySQL when more connections
are attempting to connect than the max_connections setting. It defaults
to 100 but it is often set at 1024 in distributions. An Openstack
application that uses oslo.db will go through oslo.db's create_engine()
routine which defaults the max number of connections per python process
to 15, and when the process is idle, this drops to 5.
Which means, there have to be over 60 python processes all hitting the
DB at the max to get that error, if max_connections is at 1024. Or
the connection pool is totally broken (e.g. with eventlet monkeypatching
perhaps), which would be a critical issue for me to fix.
So I'd love to see how the "too many connections" error actually
happens. Please share whatever you have on that.
I believe the distro defaults in Ubuntu are the mysql defaults, which is
151 - https://dev.mysql.com/doc/refman/5.5/en/too-many-connections.html
We've been watching a "too many connections" issue internally and I had
assumed our connections were at 100 or 150, but when I poked around i
saw that RHEL is setting this at 1024 for mariadb-galera at least. So
it's worth knowing what the number is if we see this actually happen
somewhere. Quickest way to see it is to just query for it against MySQL
itself with "show variables like 'max_connections';".
If we're allowing 15 connections per python process, and the APIs are
running in a worker mode, which means 8 workers per API server, yes,
that's going to add up really quick.
Perhaps under these scenarios we need to raise this to 1024 in devstack?
yes, that would be appropriate.
-Sean
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