[pgpool-general: 6472] Re: trusted_servers

[Alexander Dorogensky]

Awesome, thanks!

Pgpool-II should still works very well in case of 2 node cluster ( although
> recommended is min 3). And in this case even if the split brain
> happens it takes just few seconds for watchdog to detect and recover from
> it. So you can still disable  trusted_servers in your setup.


Interesting.. but that was not the case. I had to set that parameter
because pgpool wasn't detecting network partition and there would be two
recovery jobs running on both nodes.

On Wed, Mar 20, 2019 at 9:43 AM Muhammad Usama <m.usama at gmail.com> wrote:

>
> On Wed, Mar 20, 2019 at 7:09 PM Alexander Dorogensky <
> amazinglifetime at gmail.com> wrote:
> >
> > Thanks for a very detailed explanation!
> >
> > How long can it take pgpool to detect that the trusted server (one) is
> not responsive?
>
>
> Pgpool-II issues the ping command "ping -c3 trusted_server" for each
> server listed in trusted_servers list after every wd_interval seconds, and
> whenever
> ping result for every server in the trusted_servers list comes out
> negative, Pgpool node consider itself as isolated and removes itself from
> cluster.
> So effectively it takes maximum wd_interval number of seconds plus 3 ping
> attempts to detect the trusted_server is not responsive.
>
> >
> > We're using pgpool 3.6.9 and we have 2 node (primary/standby postgres
> cluster with streaming replication) configuration and each node has pgpool.
> >
> > We had to set trusted_servers because otherwise pgpool wouldn't detect
> network partition events such as when
> > network interface goes down on one of the nodes. So I believe in this
> configuration we wouldn't have been able to use
> > the pgpool's split-brain syndrome auto detection?
> >
>
> Pgpool-II should still works very well in case of 2 node cluster (
> although recommended is min 3). And in this case even if the split brain
> happens it takes just few seconds for watchdog to detect and recover from
> it. So you can still disable  trusted_servers in your setup.
>
> Also to protect against network interface going down you can use the
> interface monitoring in watchdog wd_monitoring_interfaces_list
> (see *wd_monitoring_interfaces_list* in section 5.14.7 of
> http://www.pgpool.net/docs/latest/en/html/runtime-watchdog-config.html#CONFIG-WATCHDOG-SERVER-CONFIGURATION
> )
>
>
> Thanks
> Best Regards
> Muhammad Usama
>
>
> >
> > Thank you Muhammad!
> >
> >
> >
> >
> >
> > On Wed, Mar 20, 2019 at 8:23 AM Muhammad Usama <m.usama at gmail.com>
> wrote:
> >>
> >> Hi
> >>
> >> 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
> (wd_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
> trusted_server
> >> configuration, and watchdog will take care of split-brain issue itself.
> >>
> >> Thanks
> >> Best Regards
> >> Muhammad Usama
> >>
> >>
> >>>
> >>> Thanks
> >>> _______________________________________________
> >>> pgpool-general mailing list
> >>> pgpool-general at pgpool.net
> >>> http://www.pgpool.net/mailman/listinfo/pgpool-general
>
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