[pgpool-general: 6469] Re: trusted_servers

Muhammad Usama m.usama at gmail.com
Wed Mar 20 22:23:28 JST 2019


On Wed, Mar 13, 2019 at 6:28 PM Alexander Dorogensky <
amazinglifetime at gmail.com> wrote:

> Hi everyone,
> We generally set this parameter to one host to remedy split brain
> situations but some customers have unreliable networks and therefore ping
> to that host would fail and pgpool would shut down.
> My understanding was that trusted server(s) connection will only be tested
> after degenerated state was detected (before triggering failover), is it
> correct?
> If not.. how do I configure trusted servers in a flaky network?

No thats not correct, If the trusted_server(s) are configured than
Pgpool-II try to ping the trusted_servers after every life-check interval

Basically the trusted_servers checking was introduced in the pgpool
watchdog, during the early days of watchdog, and as you mentioned its
purpose was to
mitigate the split-brain syndrome, by making sure that the Pgpool-II node
which gets isolated from the network because of network partitioning or
some other network issue removes itself from the Pgpool-II cluster.

But since Pgpool-II 3.5 there have been lots of enhancements made to the
Pgpool-II watchdog specifically in the area of guarding against the
split-brain and
other similar scenarios, and the latest versions of Pgpool-II does not
require trusted_servers configuration to detect and avoid split-brain.

So if you are using the Pgpool-II > V 3.5 and the Pgpool-II cluster is
configured with odd number of nodes (>=3) than you can safely disable the
configuration, and watchdog will take care of split-brain issue itself.

Best Regards
Muhammad Usama

> Thanks
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