Re: Monitoring streaming replication from standby on Windows

Hello

I was just wondering the same. As for the slave, it seems to me that
the "ps fax" output "postgres: startup process recovering" is at least
a quick way to check if the replication client has synced.

In a case where e.g. the slave was down for a while and then unsuccessfully
waits for WAL files which were long deleted on the master, this line changed
to "startup process waiting".

HTH,

-christian-

On Fri, 14 Dec 2012 09:52:49 -0400
Yamen LA <iyamen(at)live(dot)com> wrote:

>
> Thank you Karl.
>
> I am trying to determine on the slave itself whether streaming replication (i.e. WAL receiver process) is active or not, similar to checking pg_stat_replication on the master. In fact, this is part of a larger module I am building to control the databases and automate failovers.
>
> As for monitoring the offset between the two, what is a reasonable value for the differences between last xlog sent, received and replayed?
>
> -Yamen
>
> Date: Thu, 13 Dec 2012 19:43:53 -0600
> From: karl(at)denninger(dot)net
> To: iyamen(at)live(dot)com
> CC: pgsql-general(at)postgresql(dot)org
> Subject: Re: [GENERAL] Monitoring streaming replication from standby on Windows
>
>
>
>
>
>
> On 12/13/2012 7:36 PM, Yamen LA wrote:
>
>
>
>
> Hello,
>
>
>
> I would like to know how to check the status of the streaming
> replication from standby server on Windows. Apparently from the
> master I can use the pg table "pg_stat_replication". This table
> is, however, empty on the standby since it contains information
> about WAL sender processes and not WAL receiver.
> pg_last_xlog_replay_location and pg_last_xlog_receive_location
> also continue to be valid even when the streaming replication is
> down, so they don't help in this case.
>
> From online tutorials and PostgreSQL wiki the only way I found
> is by checking the running processes for wal sender and wal
> receiver using ps command on Unix systems. The problem is that
> on Windows, all those processes carry the same name,
> postgresql.exe.
>
>
>
> I suppose there should be some parameter to get the db engine as
> it realizes when the streaming replication is down and it logs
> that in pg_log files, but I can't seem to find such a parameter.
>
>
>
> Thank you for your help.
>
>
>
> -Yamen
>
>
>
> What are you trying to determine?
>
>
>
> If it's whether the replication is caught up, I have a small "C"
> program that will do that and have posted it before (I can do that
> again if you'd like.)
>
>
>
> If it's whether it's "up", that's a bit more complex, since you have
> to define "up."
>
>
>
> For most purposes determining that the offset between the two is
> less than some value at which you alarm is sufficient, and if you
> then alarm if you can't reach the master and slave hosts, you then
> know if the machines are "up" from a standpoint of reachability on
> the network as well.
>
>
>
> --
>
> -- Karl Denninger
>
> The Market Ticker ®
>
> Cuda Systems LLC

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