Re: [BUGS] Bug in Physical Replication Slots (at least 9.5)?

Hello,

This problem still occurs on the master.
I rebased this to the current master.

At Mon, 3 Apr 2017 08:38:47 +0900, Michael Paquier <michael.paquier@gmail.com> wrote in <CAB7nPqT8dQk_Ce29YQ0CKAQ7htLDyUHNdFv6dELe4PkYr3SSjA@mail.gmail.com>
> On Mon, Apr 3, 2017 at 7:19 AM, Venkata B Nagothi <nag1010@gmail.com> wrote:
> > As we are already past the commitfest, I am not sure, what should i change
> > the patch status to ?
> 
> The commit fest finishes on the 7th of April. Even with the deadline
> passed, there is nothing preventing to work on bug fixes. So this item
> ought to be moved to the next CF with the same category.

The steps to reproduce the problem follows.

- Apply the second patch (0002-) attached and recompile. It
  effectively reproduces the problematic state of database.

- M(aster): initdb the master with wal_keep_segments = 0
            (default), log_min_messages = debug2
- M: Create a physical repslot.
- S(tandby): Setup a standby database.
- S: Edit recovery.conf to use the replication slot above then
     start it.
- S: touch /tmp/hoge
- M: Run pgbench ...
- S: After a while, the standby stops.
  > LOG:  #################### STOP THE SERVER

- M: Stop pgbench.
- M: Do 'checkpoint;' twice.
- S: rm /tmp/hoge
- S: Fails to catch up with the following error.

  > FATAL:  could not receive data from WAL stream: ERROR:  requested WAL segment 00000001000000000000002B has already been removed


The first patch (0001-) fixes this problem, preventing the
problematic state of WAL segments by retarding restart LSN of a
physical replication slot in a certain condition.

regards,

-- 
Kyotaro Horiguchi
NTT Open Source Software Center