[pgpool-general: 4488] Re: Understanding node info and watchdog info

[Jose Baez]

*> And when the pgpool-II are configured to use watchdog, All pgpool-II
connected with watchdog*
*> exchanges the node status when ever the any backend node status
is changed.*
*>*

If I use 2 pgpool instances *without watchdog* (only 1 of them is active
and running), could I use a NFS network folder to save the "pgpool_status"
file ?
So when the second instance is running in a second machine, it will read
the same pgpool_status file (with same owner, permissions, and so on...) ?

Thanks.






On 15 February 2016 at 18:39, Muhammad Usama <m.usama at gmail.com> wrote:

> On Sun, Aug 2, 2015 at 7:20 PM, Thomas Bach <t.bach at ilexius.de> wrote:
> > -----BEGIN PGP SIGNED MESSAGE-----
> > Hash: SHA256
> >
> > Hi there,
> >
> > I configured pgpool-IIpgpool-II version 3.3.2 (tokakiboshi) and
> > Postgres to run on two separate machines in replication mode. I just
> > recently configured watchdog. At some point the two databases diverged
> > which is ok because I am currently in the testing phase.
> >
> > Now on host02 I query watchdog and obtain
> >
> > host02 # pcp_watchdog_info -v 1 host01 9898 root ****
> > Hostname     : host01
> > Pgpool port  : 5432
> > Watchdog port: 9000
> > Status       : 2
> > host02 # pcp_watchdog_info -v 1 host02 9898 root ****
> > Hostname     : host02
> > Pgpool port  : 5432
> > Watchdog port: 9000
> > Status       : 3
> >
> > So host02 is active. I obtain the exact same results when issuing
> > these queries from host01.
>
> pcp_watchdog_info utility displays the information of pgpool-II
> watchdog node, So if the pgpool-II watchdog
> cluster is configured and working without any problem, executing the
> pcp_watchdog_info on any pgpool-II node
> should always displays the same results for all pgpool-II nodes in the
> cluster.
> >
> > Anyway, when querying pcp_node_info I obtain the following:
> >
> > host02 # pcp_node_info -v 1 host01 9898 root **** 0
> > Hostname: host01
> > Port    : 5433
> > Status  : 1          <----------------------
> > Weight  : 1.000000
> > host02 # pcp_node_info -v 1 host01 9898 root **** 1
> > Hostname: host02
> > Port    : 5433
> > Status  : 1
> > Weight  : 0.000000
> > host02 # pcp_node_info -v 1 host02 9898 root **** 0
> > Hostname: host01
> > Port    : 5433
> > Status  : 3         <----------------------
> > Weight  : 0.000000
> > host02 # pcp_node_info -v 1 host02 9898 root **** 1
> > Hostname: host02
> > Port    : 5433
> > Status  : 1
> > Weight  : 1.000000
> >
>
> As pcp_node_info utility displays the status of Backend (PostgreSQL)
> nodes connected with the pgpool-II. And when the pgpool-II are
> configured to use watchdog, All pgpool-II connected with watchdog
> exchanges the node status when ever the any backend node status is
> changed. So agin when the pgpool-II watchdog is configured and working
> correctly, All pgpool-IIs in the cluster should have the same status
> of backend node. But there is some problem with your setup or in
> pgpool-II since pgpool-II on Host1 and Host2 are showing different
> status for node 0 which should never happen, Analyzing the pgpool-II
> logs of both pgpool-II would be helpful in the situation to analyze
> why pgpool-II on host02 thinks the status of PostgreSQL node 0 is down
> and what error caused this status not to get replicated with pgpool-II
> on host01.
>
> > So, as host02 sees it, host01 is down. But for host01 both itself as
> > well as host02 are perfectly sane.
> >
> > 1) Is such a state intended? I.e. is pgpool-II fully operational in
> > this mode?
>
> This is not intended and indicates a problem in pgpool-II or the
> setup. pgpool-II logs would be helpful to locate the actual problem.
> >
> > 2) What will happen when I do an insert via host02? Will it replicate
> > to host01?
> >
> > 3) And even more interesting: what will happen when I do an insert via
> > host01?
> >
>
> Both pgpool-II (on host01, and host02) will behave according to their
> local view of the PostgreSQL backend node statuses.
>
> > 4) What ways do I have at hand to resolve this issue?
>
> As described above, analyzing the pgpool-II log will give more details
> about the cause of the problem and a way to rectify it.
>
>
> Thanks
> Kind regards
> Muhammad Usama
>
> >
> > Regards
> >
> >         Thomas.
> >
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