Re: difference in multi-master replication since 2.4.57
On Thu, Mar 04, 2021 at 01:09:55PM +0100, Michael Ströder wrote:
On 3/4/21 12:20 PM, Ondřej Kuzník wrote:
> If it takes 1 second to replicate a change and a previous change
> happened x seconds before this one there's going to be a window of 1
> second where you see an x second CSN difference between the provider and
> consumer. In no way does it mean the consumer is x seconds behind.
I'm talking about the contextCSN difference being visible for several
*hours* while the changes have been already successfully replicated.
Replication delay is very short, syncrepl type is refreshAndPersist.
Don't think I've ever seen this outside slapcat (only checkpoints affect
the on-disk version). Please submit a bug if you can replicate this.
> If there's an acceptable delay of n seconds, you better wait
for that
> amount of time before raising an alarm,
And what's an appropriate value for n? 86400? ;-]
Depends where in the galaxy you place your replicas :)
> See the logic in syncmonitor[0]
Ideally I'd like to query cn=monitor whether slapd thinks replication is
in a healthy state.
Consumer will never think its replication is slow/broken (unless it gets
an actual error and you can already see that in cn=monitor). Provider
might want to expose some information but that's not implemented yet and
will not be able to spot many issues if other providers exist.
--
Ondřej Kuzník
Senior Software Engineer
Symas Corporation http://www.symas.com
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