RE: ***Conflict with recovery error***

Hi Laurenz,

Thanks for your reply.
We had set max_standby_streaming_delay = -1, but faced storage issues nearly 3.5 TB of storage was consumed.

Regards,
Abhishek P

-----Original Message-----
From: Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>
Sent: Friday, January 20, 2023 3:26 PM
To: Abhishek Prakash <abhishek(dot)prakash08(at)infosys(dot)com>; pgsql-general(at)lists(dot)postgresql(dot)org; pgsql-hackers(at)lists(dot)postgresql(dot)org; usergroups(at)postgresql(dot)org
Subject: Re: ***Conflict with recovery error***

[**EXTERNAL EMAIL**]

On Fri, 2023-01-20 at 08:56 +0000, Abhishek Prakash wrote:
> We are facing below issue with read replica we did work arounds by
> setting hot_standby_feedback, max_standby_streaming_delay and
> max_standby_archive_delay, which indeed caused adverse effects on
> primary DB and storage. As our DB is nearly 6 TB which runs as AWS Postgres RDS.
>
> Even the below error occurs on tables where vacuum is disabled and no
> DML operations are permitted. Will there be any chances to see row
> versions being changed even if vacuum is disabled.
> Please advise.
>
> 2023-01-13 07:20:12
> UTC:10.64.103.75(61096):ubpreplica(at)ubprdb01:[17707]:ERROR: canceling
> statement due to conflict with recovery
> 2023-01-13 07:20:12 UTC:10.64.103.75(61096):ubpreplica(at)ubprdb01:[17707]:DETAIL: User query might have needed to see row versions that must be removed.

It could be HOT chain pruning or an anti-wraparound autovacuum (which runs even if autovacuum is disabled).
Disabling autovacuum is not a smart idea to begin with.

Your best bet is to set "max_standby_streaming_delay = -1".

More reading:
https://apc01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.cybertec-postgresql.com%2Fen%2Fstreaming-replication-conflicts-in-postgresql%2F&data=05%7C01%7Cabhishek.prakash08%40infosys.com%7Ce50f15f9ec4a497669a208dafacc8a3c%7C63ce7d592f3e42cda8ccbe764cff5eb6%7C0%7C0%7C638098053794261389%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=%2FlYwVKhkjP23vza5yhuJfw6mcOYynDVbNIhnKRBwUu4%3D&reserved=0

Yours,
Laurenz Albe