Re: Logical replication monitoring

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От AYahorau@ibagroup.eu
Тема Re: Logical replication monitoring
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Msg-id OF8734117D.4F6AF340-ON432582E8.0036DC83-432582E8.0038791D@iba.by
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Ответ на Logical replication monitoring  (AYahorau@ibagroup.eu)
Ответы Re: Logical replication monitoring  (Rajni Baliyan <saan654@gmail.com>)
Re: Logical replication monitoring  (Achilleas Mantzios <achill@matrix.gatewaynet.com>)
Список pgsql-admin
Hello!

Thank you for your suggestion.
I  afraid this approach is not suitable for me. As a rule my postgresql log  on subscriber side contains a  bunch of the following entries:

ERROR:  terminating logical replication worker due to timeout

00000 LOG:  worker process: logical replication worker for subscription 24578 (PID 6217) exited with exit code 1

How should I handle this situation?
As I understand this is quite normal situation. But why is severity for it  an ERROR ?

I have another assumption. Could you correct me if I am wrong.
I found out in the source code that logical replication worker termination depends on wal_receiver_timeout paramer.
So I propose setting wal_receiver_timeout  to 0.
In this case I think that monitoring of the following views  pg_stat_subscription, pg_publication and pg_stat_replication  is enough.

In case if there  is some problem with connection or with replication pg_stat_replication  will show nothing because wal sender will not be working otherwise it will give some information.
Am I right? Are there any vulnerabilities in this approach ?


Best regards,
Andrei Yahorau



From:        Andrei Yahorau/IBA
To:        pgsql-admin@postgresql.org,
Cc:        Mikalai Keida/IBA@IBA
Date:        10/08/2018 13:05
Subject:        Logical replication monitoring




Hello PostgreSQL Community!

I configured logical replication for PostgreSQL 10.4 on 2 machines, set wal_level to logical, created a publication on master node and created a subscription on standby node according to the PostgreSQL documentation.
Could you please suggest an approach for replication state monitoring.

According to my experience the monitoring of pg_stat_subscription and pg_publication, pg_replication_slots unfortunately is not enough for this aim. Moreover standby database does not prohibit write operations by default and it can lead to some inconsistency between these databases.

For example a chain of queries as
SELECT pg_is_is_recovery(),
SELECT * FROM pg_stat_replication and
SELECT * FROM pg_stat_wal_receiver
provide insight into replication state for hot_standby replication.

So is there a reliable way of replication state monitoring for logical replication?

Best regards,
Andrei Yahorau

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