From: Jerry Sievers <gsievers19@comcast.net>
To: Dhirendra Singh <dhirendraks@gmail.com>
Cc: pgsql-admin@lists.postgresql.org
Subject: Re: standby server is complaining about missing wal file after
 switchover
References: 
 <CAEyh4sZtxm=f-BiakMy83WgEY8_woAb61EY0Jpc=61COKrLj8Q@mail.gmail.com>
Date: Thu, 13 Oct 2022 18:42:42 -0500
In-Reply-To: 
 <CAEyh4sZtxm=f-BiakMy83WgEY8_woAb61EY0Jpc=61COKrLj8Q@mail.gmail.com>
	(Dhirendra Singh's message of "Thu, 13 Oct 2022 19:12:43 +0530")
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Dhirendra Singh <dhirendraks@gmail.com> writes:

> Hi,
> My postgres version is 14.2
> I have setup streaming replication between a primary and a standby using replication slot and without
> archive.
> I have created replication slot "slot1" on the primary.
> I did switchover following below steps.
> 1. shutdown the primary server.
> 2. created replicated slot "slot1" on standby and promoted it to primary.
> 3. run pg_rewind on the old primary and made it standby.
> 4. started the old primary as new standby.
>
> I got following error in the new standby. it is complaining about missing wal file on the new primary.
>
> 2022-10-13 12:58:48.497 UTC [25] LOG:  fetching timeline history file for timeline 2 from primary
> server
> 2022-10-13 12:58:48.508 UTC [25] LOG:  started streaming WAL from primary at 0/B000000 on
> timeline 1
> 2022-10-13 12:58:48.508 UTC [25] FATAL:  could not receive data from WAL stream: ERROR: 
> requested WAL segment 00000002000000000000000B has already been removed
> 2022-10-13 12:58:48.509 UTC [21] LOG:  new target timeline is 2
> 2022-10-13 12:58:48.580 UTC [28] LOG:  started streaming WAL from primary at 0/B000000 on
> timeline 2
> 2022-10-13 12:58:48.580 UTC [28] FATAL:  could not receive data from WAL stream: ERROR: 
> requested WAL segment 00000002000000000000000B has already been removed
>
> why the new primary has removed the wal file even though i created replication slot on it before
> promoting.
> value of max_slot_wal_keep_size is -1 and wal_keep_size is 0

Dunno but did you call the pg_create_physical_replication_slot()
 function with arg2=true to have it immediately keep the WAL pointer?

I believe otherwise not until the slot has been connected to does it
retain anything.

HTH

>
> Thanks,
> Dhirendra.