[Pdns-dev] gmysql hangs if mysql server stops responding

John Leach john at brightbox.co.uk
Tue Apr 26 13:37:12 CEST 2011


If the mysql server stops responding (anything short of sending a tcp
reset), the gmysql backend hangs until the tcp connection times out
(many minutes by default).

Attached is a patch to set the mysql library read and write timeouts so
that if the mysql server stops responding, pdns learns about it quickly.
Coupled with the MYSQL_OPT_RECONNECT added in pdns 3, it just reconnects

This patch sets the timeout at 10 seconds and the mysql library will
retry 3 times by default, so it should be 30 seconds max before a

pdns 3 does now read the mysql config file, but I can't find any way to
set these particular options using it - I'm pretty certain they need to
be set like this, in the code.

We've used pdns in conjunction with both mysql-proxy and haproxy for
high availability and it's basically useless without this patch, as they
both depend on the client timing out and reconnecting when a backend
server goes down.


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