[Labs-l] [Wikitech-l] Maria DB

[Asher Feldman]

The production migration to MariaDB was paused for a time by the EQIAD
datacenter migration and issues involving other projects that took up my
time, but the trial production roll-out will resume this month.  All signs
still point to our using it in production.

I did a lot of query testing on an enwiki MariaDB 5.5 slave over the course
of more than a month before the first production deployment.  Major version
migrations with mysql and derivatives are not to be taken lightly in
production environments.  At a minimum, one must be concerned about query
optimizer changes making one particular query type significantly slower.
In the case of the switch to 5.5, there are several default behavior
changes over 5.1 that can break applications or change results.  Hence,
some serious work over a plodding time frame before that first production
slave switch.

Despite those efforts, a couple weeks after the switch, I saw a query
generated by what seems to be a very rare edge case from that AFTv4
extension that violated stricter enforcement of unsigned integer types in
5.5, breaking replication and requiring one off rewriting and execution of
the query locally to ensure data consistency before skipping over it.  I
opened a bug, Mathias fixed the extension, and I haven't seen any other
compatibility issues from AFTv4 or anything else deployed on enwiki.

That said, other projects utilize different extensions, so all of my
testing that has gone into enwiki cannot be assumed to fully cover
everything else.  Because of that, and because I want to continue
proceeding with caution for all of our projects, this will continue to be a
slow and methodical process at this stage.  Bugs in extensions that aren't
used by English Wikipedia may be found and require fixing along the way.

As the MariaDB roll-out proceeds, I will provide updates on wikitech-l.

Best,
Asher

On Wed, Feb 13, 2013 at 5:19 AM, Petr Bena <benapetr at gmail.com> wrote:

> Okay - so what is outcome? Should we migrate beta cluster? Are we going to
> use it in production?
>
>
> On Wed, Feb 13, 2013 at 2:08 PM, Chad <innocentkiller at gmail.com> wrote:
>
>> On Wed, Feb 13, 2013 at 8:05 AM, bawolff <bawolff+wn at gmail.com> wrote:
>> > Umm there was a thread several months ago about how it is used on
>> several
>> > of the slave dbs, if I recall.
>> >
>>
>> Indeed, you're looking for "mariadb 5.5 in production for english
>> wikipedia"
>>
>> http://www.gossamer-threads.com/lists/wiki/wikitech/319925
>>
>> -Chad
>>
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>
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