[ClusterLabs] Mysql M/S, binlogs - how to delete them safely without failing over first?

[Brett Moser]

Hi Attila,

It sounds like on failover the new slave is not having it's master
replication file & position updated.

What Resource Agent are you using to control the M/S mysql resource?

Have you investigated the Percona agent?   I performs the CHANGE MASTER TO
commands for you, and I have found it to be a good RA for my M/S MySQL
purposes.

https://github.com/percona/percona-pacemaker-agents

regards,
-Brett Moser


On Tue, Aug 18, 2015 at 2:19 PM, Attila Megyeri <amegyeri at minerva-soft.com>
wrote:

> Hi List,
>
>
>
> We are using M/S replication in a couple of clusters, and there is an
> issue that has been causing headaches for me for quite some time.
>
>
>
> My problem comes from the fact that binlog files grow very quickly on both
> the Master and Slave nodes.
>
>
>
> Let’s assume, that node 1 is the master – it logs all operations to
> binlog.
>
> Node 2 is the slave, it replicates everything properly. (It is strange,
> however, that node2 must also generate and keep binlog files while it is a
> slave, but let’s assume that this is by design).
>
>
>
> There are ways to configure mysql to keep the binlog files only for some
> time, e.g. 10 days, but I had an issue with this:
>
>
>
> To explain the issue, please consider the following case:
>
> Let’s say that both node1 and node2 are up-to-date, and we did a failover
> test on day 0.
>
> DB1 is the master, DB2 is the slave.
>
> DB1 has master position “A”, DB1 has master position “B”.
>
>
>
> After 20 days, lots of binlog files exist on both servers, I would like to
> get rid of them, as the slave is up-to-date.
>
>
>
> I decide to delete all binlog files older than 1 day by issuing “purge
> binary logs…”.
>
>
>
> I try to fail over so that DB2 becomes the master, but DB1 tries to
> connect to DB2 for replication and wants to replicate starting from a
> position that it “remembers” from the times when DB2 was the master, and
> starts to look for some binlog files that are 20 days old. Now, the issue
> is, that those old binlog files have been deleted since, and replication
> stops with error (cannot find binlogs).
>
>
>
> Am I doing something wrong here, or is something configured badly?
>
> OR am I assuming correctly that in order to purge the binlog files from
> both servers I need to make a failover first?
>
>
>
>
>
> Thank you!
>
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