[pgpool-general: 7647] Re: Can PGPool manage multiple Postgres Clusters on every node?

Tatsuo Ishii ishii at sraoss.co.jp
Mon Jul 26 10:56:57 JST 2021

> Hello,
> we are setting up a 3 nodes clusters similar to this one:
> https://www.pgpool.net/docs/latest/en/html/example-cluster.html
> we are using CentOS 7.9 physical nodes with PGPool 4.2 and PostgreSQL 12.
> We need to have on every node 4 PostgreSQL instances (1 for prod, 1 for
> pre-production, 1 for test and 1 for dev), all of them must be in streaming
> replication with the other 2 nodes.
> Can PGPool manage such configuration? From the documentation we didn't find
> any reference.
> We are thinking to create 4 different pgpool instances, each one with its
> set of files and tcp port, is this a supported configuration?

The short answer is no.

Pgpool-II assumes that there's only one streaming replication primary
server exists among PostgreSQL instances. That means:

Suppose you have following PostgreSQL instances:

"A" group for "prod": A1, A2, A3

Pgpool-II can manage A1, A2 and A3, assuming that one of A1, A2,
A3 is the primary server and rest of it are standby servers.

"B" group for "pre-production": B1, B2, B3

Pgpool-II can manage B1, B2 and B3, assuming that one of B1, B2,
B3 is the primary server and rest of it are standby servers.

*BUT* a Pgpool-II instance cannot manage A group and B group altogeter
at the same time.

So it seems you have 4 groups of PostgreSQL instances (prod,
pre-production, test and dev), you can manage each group by assigning
4 Pgpool-II instances to each. In this case each Pgpool-II instance is
completely separated and will not communicate each other. I am not
sure what you can achieve in this configuration.

Best regards,
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php

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