[pgpool-general: 9213] Re: Load balancing of write queries among health-checked nodes

[Tatsuo Ishii]

Hi,

> Hello. I have a PostgreSQL high availability cluster with Pgpool-II, but I don't use the virtual IP feature so my clients don't know which node to send queries to. DNS round-robin is not a solution because it can't distinguish between healthy and dead nodes.
> 
> I thought about having a Pgpool-II instance on each client (client Pgpool-II -> cluster Pgpool-II -> PostgreSQL), but AFAIK it can't distribute write queries.

I am not sure I fully understand your requirement but I think you can
do something like:

client-A -> pgpool-A -+
                      |
client-B -> pgpool-B -+- PostgreSQL (primary and standby)
                      |
client-C -> pgpool-C -+

Here client-A, client-B and client-C are PostgreSQL compatible
clients, for example psql.

pgpool-A, pgpool-B and pgpool-C are pgpool cluster with watchdog configured.
client-A, client-B and client-C can send read or write queries to
pgpool-A, pgpool-B or pgpool-C respectively.

One downside of the configuration is, if pgpool-A goes down, client-A
cannot send queries to pgpool-A. client-A has to switch the connection
to pgpool-B or pgpool-C if it wants to continue processing.

Best reagards,
--
Tatsuo Ishii
SRA OSS K.K.
English: http://www.sraoss.co.jp/index_en/
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