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Re: On the issue of Seconds_behind_master and Parallel Replication



Is it possible to know how many transactions/operations slave is behind the
master ?
Assume in above that master is idle for several days, if master then
executes a one
transaction, does that mean that slave is behind the master also several
days ?

R: Jan

On Thu, Oct 22, 2015 at 9:12 AM, Kristian Nielsen <knielsen@xxxxxxxxxxxxxxx>

> Kristian Nielsen <knielsen@xxxxxxxxxxxxxxx> writes:
> >  - Should Seconds_Behind_Master be changed as per above in parallel
> >    replication (from 10.0 on)?
> >  - If so, should the change to Seconds_Behind_Master also be done in the
> >    non-parallel case in 10.1? What about 10.0?
> So there seems to be agreement that Seconds_Behind_Master should be changed
> in 10.1 to only update on commit (also in non-parallel case). This does
> seem
> a better behaviour.
> One consequence of this is the following: Suppose the master is idle for 1
> hour. The Seconds_Behind_Master is reported as 0 on a slave that is up to
> date. Suppose now the master executes a transaction. While that new
> transaction is being applied, the Seconds_Behind_Master will be reported as
> 3600 (one hour), then go back to zero.
> This is arguably the correct value - the slave is indeed in the state of
> the
> master one hour ago while executing that transaction. But I still wonder if
> this will not just cause another kind of confusion with users (or existing
> monitoring tools), as they will interpret it as the slave being far behind
> the master. While in reality it is only one transaction behind.
>  - Kristian.
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