Graph sql connection count with munin

[adehnert]

#328 added nagios monitoring of used connections. In tuning those thresholds (and for fun), it would be nice if munin graphed the number of (total and max per-user) connections to sql as well.

[adehnert]

p-k has this for total connections, but does not appear to graph max per-user connections, which is the alert that fires more often. Adding total connections to k-s/s-b seems questionably worthwhile, but adding per-user to p-k is probably still worthwhile.

(Since this was apparently unclear, this is not "one number for each user", which achernya correctly points out would be a privacy issue and impossible to read. This is a single number, which is the number of connections the current heaviest user has.)

[adehnert]

It looks like munin (unlike nagios) gets connection counts from SHOW GLOBAL STATUS, which means that fixing this probably involves more significant changes than "just copy a line and change it slighly", unfortunately.

[adehnert]

s-b now has total connections. k-s is effectively dead. Nothing has per-user connections yet.

[adehnert]

I think for per-user connections we probably want to build off of ​https://github.com/munin-monitoring/contrib/blob/master/plugins/mysql/mysql_aggregate_.

[adehnert]

Okay, munin is now graphing per-user connections on p-k --- ​http://sipb-noc.mit.edu/munin/sql.mit.edu/primary-key/mysql_aggregate_user_conns.html.

[adehnert]

I set this up on s-b as well (​https://sipb-noc.mit.edu/munin/sql.mit.edu/sliced-bread/mysql_aggregate_user_conns.html), and submitted a pull request for the modified mysql_aggregate_ plugin (​https://github.com/munin-monitoring/contrib/pull/330), so I think this is done.