[RADIATOR] mysql DBI timed out connections and too many open files (sockets)

Rauno Tuul raunz at hot.ee
Fri Apr 14 10:56:28 UTC 2017


The issue occurs, when attempting to establish a connection. For example
the host is totally down or firewalled.
Is the TCP connection has been established, then there's no problem.

Easy way to reproduce the issue, is to drop mysql traffic with iptables.
Example setup:
        <AuthBy SQL>
                DBSource                dbi:mysql:dbname:
                Timeout                 1
                FailureBackoffTime      1
Then drop the traffic with 'iptables -A INPUT -i lo -p tcp -m tcp
--dport 3306 -j DROP' and hit the instance with radpwtst every second.
If the debian systemd set the open file limit to 1024, then the instance
will collapse within 20 minutes.

kind regards,

On 14.04.2017 09:56, Heikki Vatiainen wrote:
> On 30.03.2017 13:54, Rauno Tuul wrote:
>> Every time, when a DBI mysql connection times out, a new socket is
>> opened. These sockets, which never get a reply (e.g. conn refused) from
>> server, idle forever - each one consumes an "open file".
> Hello Rauno, I thought I'd let you know we did see your message but do
> not have any updates yet. There's one question about the above: when you
> say a connection times out, is this:
> - a timeout when attempting to establish a connection, or
> - a timeout when doing a query
> That is, do you see the problem with new connection attempts or existing
> connections that are in active use but then timeout.
> Thanks,
> Heikki

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