Re: Shared WAL archive between master and standby: WALs not always identical

Master is streaming directly to standby. Both master and standby are
pushing WALs to archive.

My point is that in case that master crashed completely (and we failover to
standby) and wal archiver on master didn't push everything to wal archive,
we would still have a wal pushed from slave. Therefore there is no
interruption in WAL stream.

Regards,
Sasa

On 28 February 2017 at 01:57, Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com>
wrote:

> On 02/27/2017 04:40 PM, Sasa Vilic wrote:
>
>> Hallo,
>>
>> I am trying to setup shared WAL archive between master and standby.
>> Standby is synchronously streaming from master and both servers run with
>> archive_mode = always. The ideas is that when promoting standby to
>> master we would not missed WALs.
>>
>
> I seem to be missing the point of duplicating your effort.
>
> You are doing this, correct?:
>
> Master WAL --> WAL archive <--
> |
> Master stream --> Standby --> |
>
> I can't see how the Standby contributes anything to the archive that it
> does not already have from the Master?
>
>
>
>> My problem is that sometimes WAL uploaded from master and from slave are
>> not 100% identical. In most cases they are but occasionally they are
>> not. I have written small script that ensures that upload is free of
>> race condition and I log md5 sum of each WAL. Aren't WALs from master
>> and standby supposed to be identical? After all, standby is just
>> consuming WAL that it is receiving from master ...
>>
>> Or do you have any better suggestion on how to achieve continuous
>> incremental backup?
>>
>> Thanks in advance
>>
>
>
> --
> Adrian Klaver
> adrian(dot)klaver(at)aklaver(dot)com
>