Re: speed up a logical replica setup

From: Shlok Kyal <shlok(dot)kyal(dot)oss(at)gmail(dot)com>
To: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
Cc: Euler Taveira <euler(at)eulerto(dot)com>, vignesh C <vignesh21(at)gmail(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, Peter Eisentraut <peter(at)eisentraut(dot)org>, pgsql-hackers(at)lists(dot)postgresql(dot)org, Andres Freund <andres(at)anarazel(dot)de>, Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com>
Subject: Re: speed up a logical replica setup
Date: 2024-01-04 06:51:54
Message-ID: CANhcyEUdYCR9oSt4HsZRqYZZVXsb4x-HoPGqDSxSeA2SYz-YGg@mail.gmail.com
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Hi,
I was testing the patch with following test cases:

Test 1 :
- Create a 'primary' node
- Setup physical replica using pg_basebackup "./pg_basebackup –h
localhost –X stream –v –R –W –D ../standby "
- Insert data before and after pg_basebackup
- Run pg_subscriber and then insert some data to check logical
replication "./pg_subscriber –D ../standby -S “host=localhost
port=9000 dbname=postgres” -P “host=localhost port=9000
dbname=postgres” -d postgres"
- Also check pg_publication, pg_subscriber and pg_replication_slots tables.

Observation:
Data is not lost. Replication is happening correctly. Pg_subscriber is
working as expected.

Test 2:
- Create a 'primary' node
- Use normal pg_basebackup but don’t set up Physical replication
"./pg_basebackup –h localhost –v –W –D ../standby"
- Insert data before and after pg_basebackup
- Run pg_subscriber

Observation:
Pg_subscriber command is not completing and is stuck with following
log repeating:
LOG: waiting for WAL to become available at 0/3000168
LOG: invalid record length at 0/3000150: expected at least 24, got 0

Test 3:
- Create a 'primary' node
- Use normal pg_basebackup but don’t set up Physical replication
"./pg_basebackup –h localhost –v –W –D ../standby"
-Insert data before pg_basebackup but not after pg_basebackup
-Run pg_subscriber

Observation:
Pg_subscriber command is not completing and is stuck with following
log repeating:
LOG: waiting for WAL to become available at 0/3000168
LOG: invalid record length at 0/3000150: expected at least 24, got 0

I was not clear about how to use pg_basebackup in this case, can you
let me know if any changes need to be made for test2 and test3.

Thanks and regards
Shlok Kyal

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