pg_rewind issue

Hi All,

pg_rewind is failing to bring an old master back into a workable state. I'm
wondering if I'm missing a step?

EDB 9.6.4 using pg_backrest for archive management.

High write rate throughout this process.

Steps to cause:

- Stop old master
- Promote old standby to new master
- Force checkpoint on new master
- Run pg_rewind (1) on old master
- Start old master with correct recovery.conf

After all archives are pulled from the new master seeing this in the
standby logs:

2017-09-07 14:59:40 AEST [117796]: [3-1] user=,db=,client= (0:00000)LOG:
entering standby mode
2017-09-07 14:59:41 AEST [117796]: [4-1] user=,db=,client= (0:00000)LOG:
restored log file "00000015.history" from archive
2017-09-07 14:59:42 AEST [117796]: [5-1] user=,db=,client= (0:00000)LOG:
restored log file "0000001500000C7400000044" from archive
2017-09-07 14:59:42 AEST [117796]: [6-1] user=,db=,client= (0:00000)LOG:
unexpected pageaddr C6F/C8000000 in log segment 0000001500000C7400000044,
offset 0
2017-09-07 14:59:42 AEST [118045]: [1-1] user=,db=,client= (0:00000)LOG:
started streaming WAL from primary at C73/A9000000 on timeline 21
2017-09-07 14:59:42 AEST [118045]: [2-1] user=,db=,client= (0:XX000)FATAL:
could not receive data from WAL stream: ERROR: requested WAL segment
0000001500000C73000000A9 has already been removed

When Iook at timeline 15 I see this:

20 C74/45000000 no recovery target specified+

As 0000001500000C73000000A9 > 0000001500000C7400000044 I'm confused why
this WAL would be required? It's never been created on either server
(although the same suffix does exist in timeline 14).

Cheers,
James Sewell

(1) /usr/edb/as9.6/bin/pg_rewind --target-pgdata=/ppas/9.6/data/pg_data
--source-server="host =10.154.19.24 port=5432 user=postgres
dbname=postgres"

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