Re: WAL archive on slave

Hi again,

I just realised I asked this question around a year ago (for a different
reason actually) and you answered me then! Amazing!

Your answer then was:

It works fine, only the server will not generate WAL while
> it is in recovery. As soon as you promote the standby,
> it will archive ist WALs.

Is this still correct? If it is the the only way that I could achieve what
I wanted would be to set wal_keep_segments high enough then they will all
be archived on promotion?

I'm still not sure why they wouldn't be archived on the slave, seen as they
show up in the directory? Is there a limitation I'm not thinking about here?

Cheers,

James Sewell,
PostgreSQL Team Lead / Solutions Architect
______________________________________

Level 2, 50 Queen St, Melbourne VIC 3000

*P *(+61) 3 8370 8000 *W* www.lisasoft.com *F *(+61) 3 8370 8099

On Mon, Feb 10, 2014 at 11:16 AM, James Sewell <james(dot)sewell(at)lisasoft(dot)com>wrote:

> Thanks for the reply Albe.
>
> I have WAL archiving enabled on both my servers, but it only happens on
> the master.
>
> When I promote the slave to be the new master then it will start archiving
> automatically, which suggests that my configuration is correct.
>
> Can you think of anything else which might cause this?
>
> Cheers,
>
>
> James Sewell,
> PostgreSQL Team Lead / Solutions Architect
> ______________________________________
>
>
> Level 2, 50 Queen St, Melbourne VIC 3000
>
> *P *(+61) 3 8370 8000 *W* www.lisasoft.com *F *(+61) 3 8370 8099
>
>
>
> On Fri, Feb 7, 2014 at 7:30 PM, Albe Laurenz <laurenz(dot)albe(at)wien(dot)gv(dot)at>wrote:
>
>> James Sewell wrote:
>> > My understanding is that WAL archiving can not be enabled on the slave
>> in a streaming replication
>> > pair.
>>
>> It can be enabled. Did you try it?
>>
>> > If this is correct, is there a reason behind it? I can see logs showing
>> up in pg_xlog, so could they
>> > not be archived?
>>
>> These are files containing the WAL data replicated from the master.
>> They won't be archived.
>>
>> > The reason I ask is if this happened it would allow the following with
>> a streaming replication pair
>> > (A,B):
>> >
>> >
>> > 1. Start A as master
>> > 2. Attach B as slave using basebackup
>> > 3. work ....
>> > 4. Promote B to master
>> >
>> > 5. Restore A from a scheduled backup to a time before promotion
>> > 6. Attach A as slave pointing at B's WAL archive
>> >
>> > If we used A's WAL archive in this case and A had writes after the
>> promotion then we would get
>> > timeline errors.
>>
>> You shouldn't with 9.3, because in that case A would follow the
>> timeline switch introduced by B's promotion rather than its old timelime.
>>
>> http://www.postgresql.org/message-id/E1TjCRc-00084r-1H@gemulon.postgresql.org
>>
>> I may be missing something there since I have never tried it.
>>
>> > As far as I can tell, using the WAL archive from B would resolve this
>> issue.
>>
>> That should work in any event.
>>
>> Yours,
>> Laurenz Albe
>>
>
>

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