← Back to team overview

maria-developers team mailing list archive

Re: [External] Obsolete GTID domain delete on master (MDEV-12012, MDEV-11969)


Kristian, hello.

The patch is ready for review and can be located on bb-10.1-andrei,
(Ignore https://github.com/MariaDB/server/pull/459 which specified 10.2
base by mistake)

In case you won't be able to, I'll find replacement, no worries.

Have a good time.


> Kristian, thanks for more remarks!
>>>> If you “forget" the domain on the upstream server what happens if
>>>> there
>>>> are downstream slaves?  I think you’ll break replication if they
>>>> disconnect
>>>> from this box and try to reconnect. Their GTID information will no
>>>> longer match.
>>>> IMO and if I’ve understood correctly this is broken.
>> It should not break replication. It is allowed for a slave with GTID
>> position 0-1-100,10-2-200 to connect to a master that has nothing in
>> domain
>> 10, this is normal.
> To me in a sense this is "implicit" IGNORE_DOMAIN_IDS on domains that
> master
> does not have.
>> I am not sure what the use-case of replicating DELETE DOMAIN to a
>> slave
>> would be. Domain deletion does not have a point-in-time property
>> like normal
>> transactions, so it does not help to have it replicated inline in
>> the event
>> stream. If it has an effect on a slave, this effect occurs only when
>> the
>> slave is restarted/reconnected.
> The use-case must've been the suspected loss of connectivity by
> slaves.
>>>> I really think there’s a need to indicate what domains should be
>>>> forgotten/ignored
>> If CHANGE MASTER ... IGNORE_DOMAIN_IDS is fixed to also ignore the
>> extra
>> domains on master upon connect, it is probably a better way to
>> ignore
>> domains in many cases. It is persisted (in the slave's master.info),
>> and it
>> can be set individually for each slave, which is more flexible (what
>> if one
>> slave needs to ignore a domain but another slave needs to replicate
>> it?).
>>>    >KN> The procedure to fix it will then be:
>>>    >> 
>>>    >> 1. FLUSH BINARY LOGS, note the new GTID position.
>>>    >> 
>>>    >> 2. Ensure that all slaves are past the problematic point with
>>>    >> MASTER_GTID_WAIT(<pos>). After this, the old errorneous
>>>    >> binlog files
>>>    >> are no
>>>    >> longer needed.
>>>    >> 3. PURGE BINARY LOGS to remove the errorneous logs.
>>>    >> 
>> So this was what I suggested at some point related to
>> MDEV-12012. But
>> probably this is not the best suggestion, as I realised later.
>> 1. In MDEV-12012, two independent masters were originally using the
>> same
>> domain id, so their history looks diverged in terms of GTID. This
>> can be
>> fixed by injecting a dummy transaction to make them up-to-date with
>> one
>> another in that domain.
>> Deleting (possibly valuable) part of the history is
>> not needed.
>> 2. Another case, a slave needs to ignore the part of the history on
>> a master
>> connected with some domain. IGNORE_DOMAIN_IDS, once fixed, can do
>> this,
>> again there is no need to delete possibly valuable history on the
>> master.
> Right. The feature we've been discussing solely deals with p.3.
>> 3. At some point, a domain that was unused for long may no longer
>> appear
>> anywhere, _except_ in gtid_binlog_state and gtid_slave_pos. This may
>> eventually clutter the output and be an annoyance. The original idea
>> with
>> FLUSH BINARY LOGS DELETE DOMAIN was to allow to fix this annoyance
>> by
>> removing such domains from gtid_binlog_state once they are no longer
>> needed
>> anywhere.
>> I am not sure my original suggestion of using PURGE LOGS was ever a
>> good
>> idea, or is ever needed.
> I think it remains as optional which I wrote in my reply last night.
> Cheers,
> Andrei
>>  - Kristian.
> _______________________________________________
> Mailing list: https://launchpad.net/~maria-developers
> Post to     : maria-developers@xxxxxxxxxxxxxxxxxxx
> Unsubscribe : https://launchpad.net/~maria-developers
> More help   : https://help.launchpad.net/ListHelp

Follow ups