[pgpool-general: 3225] Re: pgpool with Slony replication delay

Tatsuo Ishii ishii at postgresql.org
Fri Oct 17 08:06:01 JST 2014

> Hi everyone,
> I have encountered a problem with pgpool using Slony for replication to
> slaves.  The client to pgpool in my case is an API, so requests come in
> concurrently on independent connections.  If we have an insert directly
> followed by a select for that record, the select is load balanced between
> the master and slave, resulting in a 50% chance of a failure.  Since the
> select ends up coming from a separate httpd child process, there is no way
> to keep the insert and select in the same transaction.
> Am I missing something in the documentation and configs?  Can pgpool
> intelligently recognize specific records that have been inserted to a
> table, then direct all selects for that record to the master until Slony
> has replicated it to the slaves?

No. That's the limitaion of Slony (more presicely, asynchronous
replication systems include streaming replication).

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

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