No way to increase the net_*_timeout values for the mysqldump-lvm mysqld process

[Marc - A. Dahlhaus]

There is currently no way to set the net-read-timeout and net-write-timeout values in the mysqld process dumping contents from a snapshot.

We are using a NFS share that is provided by a NAS that does inline deduplication of the data.
We get "connection lost during query" errors while running the mysqldump-lvm plugin.

I could fix this by adding a way to set the timeouts for the snapshot mysqld process.

[Andrew Garner (muzazzi)]

This is similar to the request in https://bugs.launchpad.net/holland-backup/+bug/752048 where a more general mysqld-options config parameter is being added to allow passing arbitrary options to the mysqld commandline. Probably allow for additional options in the holland backupset's [mysqld] section also makes sense here.

I am surprised that net-*-timeout was causing a problem here - those are pretty high at 30 and 60 seconds by default. Did this resolve your issue? Offhand, I was more suspect of mysqld crashing - someone recently mentioned that holland is not taking innodb-log-files-in-group into account (and effectively defaulting to 2), for instance, which can lead to a crash of the snapshot mysqld instance. Perhaps there are other mysqld options not being considered correctly here.

[Marc - A. Dahlhaus (mad-wol)]

mysqldump gets the running session closed during the dump of a large table that had more than a million rows in it.

The connection close was on a different row every night and the networks were not saturated.

It could be that the nas was a bit slower than usual but we track the nas with unit-tests and there were no failures protocolled...

We had the same problems without holland in the past with mysqldump and fixed them by increasing the net-{read,write}-timeout to higher values. There might be a better solution for this problem...

I read over BUG 752048 and got to the point that the options line could get quite large if we put everything we want to set in there...

There are cases where you have to use an option (because there is no value to set in my.cnf) and there are cases where it would be better to add something like the following:

[mysqld]
include = <path to a my.cnf configuration file that gets included>