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Re: Replicating same server_id problem


Kristian Nielsen <knielsen@xxxxxxxxxxxxxxx> writes:

> The main problem I see is what should be the default? I suppose we cannot
> safely change the default for --replicate-same-server-id. On the other hand,
> if users explicitly set --replicate-same-server-id=0, then it really does not
> seem correct that some events with same server id are nevertheless replicated
> depending on some complicated GTID semantics. So the curse of backwards
> compatibility seems to hit here...

Hm, on second thoughts...

CHANGE MASTER TO ... master_use_gtid is a new feature, so backwards
compatibility does not really apply. And in GTID mode, we have a better way to
prevent loops - the seq_no. Even in non-strict mode this can be relied on for
our own server_id, at least.

So perhaps it is better to just say that --replicate-same-server-id does not
apply to GTID mode at all. Instead, in GTID mode, if we receive an event with
our own server_id and smaller seq_no than what we already have, we skip
it. Otherwise we apply it. That should be correct in the important use-case
that you mentioned (restoring old backup), as well as in ring topologies.

I need to think on this a bit more to be sure, but it seems like a possible

 - Kristian.

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