Whenever you do switch-over, postgres-wal creates a new timeline, which
simplifies managing PITR process.
During switch-over(promoting B as master) you had some delta records written to
A, that’s where it causes this timeline issue.
Now since A had some delta records, it can’t replicate from B and hence you are
getting that issue.
Now once your master A can’t become slave of B.
— A
> On 02-Aug-2018, at 2:39 AM, Richard Schmidt
> wrote:
>
> We have been struggling to get pr_rewind to work. In desperation we have
> been trying to make the use case as simple as possibleJ
>
> We have two databases servers running Postgres 10 on two different machine in
> the normal Primary/Standby configuration.
> Both machines write their WAL archive logs to the same shared drive (called
> /ice_dev/wal_archive).
> The configuration has the following terms
>archive_mode = always
> archive_command = 'test ! -f /ice-dev/wal_archive/%f && cp %p
> /ice-dev/wal_archive/%f'
> full_page_writes = on
> wal_log_hints = on
> Checksums are enabled
>
> Our procedure that runs on machine A and B is as follows:
>
> Build new databases on A and B, and configure A as Primary and B as Standby
> databases.
> Make some changes to the A (the primary) and check that they are replicated
> to the B (the standby)
> Promote B to be the new primary
> Switch of the A (the original primary)
> Add the replication slot to B (the new primary) for A (soon to be standby)
> Add a recovery.conf to A (soon to be standby). File contains
> recovery_target_timeline = 'latest' and restore_command = 'cp
> /ice-dev/wal_archive/%f "%p"
> Run pg_rewind on A – this appears to work as it returns the message ‘source
> and target cluster are on the same timeline no rewind required’;
> Start up server A (now a slave)
>
> At this point A is in a read only mode but not replicating. Its logs contain
> the following repeating message
>
> 2018-08-01 20:30:58 UTC [7257]: [1] user=,db=,app=,client= FATAL: could not
> start WAL streaming: ERROR: requested starting point 0/600 on timeline 1
> is not in this server's history
> DETAIL: This server's history forked from timeline 1 at 0/57639D0.
> cp: cannot stat ‘/ice-dev/wal_archive/0002.history’: No such file or
> directory
> cp: cannot stat ‘/ice-dev/wal_archive/0003.history’: No such file or
> directory
> cp: cannot stat ‘/ice-dev/wal_archive/0002.history’: No such file or
> directory
> 2018-08-01 20:30:58 UTC [6840]: [48] user=,db=,app=,client= LOG: new
> timeline 2 forked off current database system timeline 1 before current
> recovery point 0/698
> cp: cannot stat ‘/ice-dev/wal_archive/00010006’: No such file
> or directory
>
> We can see the 0002.history file in B’s wal directory…..but it never
> appears in the wal_archive directory – not even if we issue a checkout or
> even restart the server.
> 0003.history does not appear to exist on either of the machines.
>
> Any ideas what we are doing wrong?
> Thanks. Richard
>
>
>
>
>
>
>
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