Re: wait event and archive_command

On 2021/10/21 23:55, Bharath Rupireddy wrote:
>> Also how about adding wait events for other commands like
>> archive_cleanup_command, restore_command and recovery_end_command?
> 
> +1 for the wait event.

Thanks!
I added the wait events for also restore_command, etc into the patch.
I attached that updated version of the patch.


> The following activitymsg that are being set to ps display in
> XLogFileRead and pgarch_archiveXlog have come up for one of our
> internal team discussions recently:
> 
>              snprintf(activitymsg, sizeof(activitymsg), "waiting for %s",
>                       xlogfname);
>              set_ps_display(activitymsg);
> 
>          snprintf(activitymsg, sizeof(activitymsg), "recovering %s",
>                   xlogfname);
>          set_ps_display(activitymsg);
> 
>      snprintf(activitymsg, sizeof(activitymsg), "archiving %s", xlog);
>      set_ps_display(activitymsg);
> 
> The ps display info might be useful if we run postgres on a stand
> alone box and there's someone monitoring at the ps output, but it
> doesn't help debugging after an issue has occurred. How about we have
> the following statements which will be useful for someone to look at
> the server logs and know what was/is happening during the recovery and
> archiving.

If an issue occurs while the command is executing,
the error message is logged, isn't it? Isn't that enough for your case?


> IMO, we should also have the elog statement.
> 
> elog(LOG, "waiting for %s", xlogfname);
> elog(LOG, "recovering %s"", xlogfname);
> elog(LOG, "archiving %s", xlog);

I'm afraid that some people think that it's noisy to always log those messages.


> Another idea could be to have a hook emitting the above info to
> outside components, but a hook just for this purpose isn't a great
> idea IMO.

Yes, this idea sounds overkill to me.

Regards,

-- 
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION