MySQL 4.x Replication "relay-log"

[z0s0]

After upgrading to 4.x I noticed the introduction of relay logs. I never saw them in 3.x so I presume it's a new "feature"?

Essentially the slave server now saves every command from the masters' update log as it receives them. It writes them to the local filesystem, apparently after - not before - executing them.

Why? I have no idea. I can't see any real use for this.

But whats far more annoying is that I cannot find _any_ way to rotate / rollover / DELETE! this stuff short of stopping and starting MySQL.

Which I'm sure none of you like me doing when you're in the middle of a post ;-) But if fills up around 300mb every couple of days so something needs to be done.

Anyone have any suggestions?

[z0s0]

no one has any idea?
;-)

[MattR]

According to this page they are actually written *before* execution and *should* clear out. There are more elegant solutions to this problem but that is what there is to work with.

In any rate, a quick search of MySQL.com shows that, in the Rep Options there are two keys that look promising:
relay-log-purge
and
relay-log-space-limit

Read the descriptions carefully and come up with a good log-limit and the first option should ensure it doesn't get too much larger than that.

[z0s0]

Thanks for that Matt.

I was wondering why I hadn't noticed this before, then realised "Available since MySQL 4.1.1" isn't much good to me since the 4.1 release is in Alpha.

I wonder if the space-limit one will work on its own...

[MattR]

Thanks for that Matt.
I wonder if the space-limit one will work on its own...

It sounds like it isn't! I would suspect that, since this is new and there are not a lot of 4.1.1 rep users that this could be a bug. Try searching their bugtraq (do they have one?) and if not, submit a bug!

[z0s0]

Yeah no joy with the space-limit one. It kindly just stopped replicating alogether once it reached that limit. Should have known ;-)

Not using 4.1 yet, still 4.0. I've been keeping an eye on the bug tracker... maybe I should bite the bullet and submit one.