[Pgpool-general] Questions about health check etc.

[Tatsuo Ishii]

> Tatsuo,
> 
> I can't determine from the docs how to use the health check.  Can you explain?
> 
> That is, how does the healthcheck work, does it require "trust" or "pgpass" 
> authentication, and what happens when the health check fails?

It sends the startup packet to postmaster, reads reply and finally
sends "good-bye" packet. If these all are well, pgpool assumes
PostgreSQL is ok. pgpool does not care if the auth succeeded or
not. You could even use non-existing user for health
checking. However, failed authentications or invalid users will flood
the PostgreSQL's log file.

pgpass will not work with pgpool since pgpass is one of the
functionalities libpq provides. Because pgpool does not relies on
libpq, pgpass will not be handled until pgpool implements it (any
volunteers?).

When health check fails, pgpool does failover or degeration.

> Also, how does replication_stop_on_mismatch work?

If replies from PostgreSQL do not agree, pgpool starts failover or
degeration.
--
Tatsuo Ishii

> Thanks!
> 
> -- 
> --Josh
> 
> Josh Berkus
> Aglio Database Solutions
> San Francisco
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