FAQ
I'm testing synchronous replication on 9.2devel - both instances are on a single machine.

The primary shows synchronous_commit = on
and synchronous_standby_names = ''.

The standby receives updates fine.

Now, does the 'synchronous_commit = on' absolutely mean that the session is sync-replicating?
Could it be non-synchronously replicating?

If so, this information in the manual seems wrong:

"
25.2.6.1. Basic Configuration

Once streaming replication has been configured, configuring synchronous replication requires only
one additional configuration step: synchronous_standby_names must be set to a non-empty value.
"
( the 'must be set' part )


Two questions:

1. How to query a session to make absolutely sure that replication is actually synchronous?

2. Does sync-repl really need synchronous_standby_names to be set?



Thank you,

Erik Rijkers

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  • Simon Riggs at Jul 1, 2011 at 3:23 pm

    On Fri, Jul 1, 2011 at 2:42 PM, Erik Rijkers wrote:

    Two questions:

    1. How to query a session to make absolutely sure that replication is actually synchronous?
    Check synchronous_standby_names and synchronous commit for appropriate values.
    2. Does sync-repl really need synchronous_standby_names to be set?
    Yes

    Unset => "synchronise with zero servers" => asynchronous

    --
    Simon Riggs                   http://www.2ndQuadrant.com/
    PostgreSQL Development, 24x7 Support, Training & Services
  • Jaime Casanova at Jul 1, 2011 at 4:28 pm

    Simon Riggs writes:
    On Fri, Jul 1, 2011 at 2:42 PM, Erik Rijkers wrote:

    Two questions:

    1. How to query a session to make absolutely sure that replication is actually synchronous?
    Check synchronous_standby_names and synchronous commit for appropriate values.
    also check pg_stat_replication

    --
    Jaime Casanova www.2ndQuadrant.com
    Professional PostgreSQL
    Soporte 24x7, desarrollo, capacitación y servicios

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