Re: Streaming replication and an archivelog

On Fri, May 8, 2015 at 2:29 PM James Sewell <james(dot)sewell(at)lisasoft(dot)com>
wrote:

> Hello All,
>
> I am running 9.4 on Centos.
>
> I have three servers, one master and two slaves. The slaves have the
> following recovery.conf
>
> standby_mode = 'on'
> primary_conninfo = 'user=postgres host=mastervip port=5432'
> restore_command = 'scp -o BatchMode=yes postgres(at)backuphost:/archived_wals/%f
> %p'
> recovery_target_timeline= 'latest'
>
> Is there any way to combine following
>
> - a master switch (ie: if node1 dies and node2 is promoted then node3
> follows node2)
> - using a WAL archive, such that if node2 goes down for two days it
> will get WALs from the archive if they are no longer on the master
>
> At the moment the master switch works fine, but if I was to have a WAL
> archive with multiple timelines in it then I would end up in the newest
> timeline.
>

The timeline switch would happen whenever do a standby promotion (or PITR)
in which case you want the 2nd standby to follow the newly promoted master
i.e. it should be following the new timeline.

> I suppose what I want is the following:
>
> If I am a streaming replica only follow streamed timeline switches, not
> archive timeline switches.
>

I am trying to guess when would these two be different (unless there are
two different masters writing to the same archive which I suppose is wrong
anyways).

Can you write down an example for clarity so that others can understand
your scenario better?

> Obviously if I am not a streaming replica I need to follow archive
> timeline switches so I don't break PIT recovery.
>
> Possible?
>
>
> James Sewell,
> PostgreSQL Team Lead / Solutions Architect
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