Re: XLogArchivingActive

Simon Riggs wrote:
> On Thu, 2006-05-25 at 17:25 +0200, Andreas Pflug wrote:
>

>
>>Currently, I have to
>>edit postgresql.conf and SIGHUP to "turn on archiving" configuring a
>>(hopefully) writable directory, do the backup, edit postgresql.conf and
>>SIGHUP again. Not too convenient...
>
>
> You're doing this for pgAdmin right?

Not yet, just trying to manage a server.

>
> My understanding was that we had the tools now to edit the
> postgresql.conf programmatically?
>
> Seems like its not too convenient to change the way the server operates
> to do this, as long as we solve the SIGHUP/postgresql.conf problem. I'm
> also not that happy about curtailing people's options on backup either:
> if people decided they wanted to have a mixture of isolated on-line
> backup (as you suggest), plus active archiving at other times they would
> still have the problems you suggest.

Why?
My suggestion is to redefine XLogArchivingActive. Currently, it tests
for non-null archive_command. I propose
bool XlogArchivingActive()
{
if (XLogArchiveCommand[0] == 0)
return false;
return (XLogPermanentArchive // from GUC
|| OnlineBackupRunning()); // from pg_start_backup
}

The people you mention simply have XLogPermanentActive=true in
postgresql.conf, delivering the current behaviour.

>
> Not sure what the edit commands are offhand, but we would need the
> following program:
>
> - edit postgresql.conf
> - pg_reload_conf()
> - wait 30
> - pg_start_backup('blah')
> - backup
> - pg_stop_backup()
> - unedit postgresql.conf
> - pg_reload_conf()
>
> Which could then be wrapped even more simply as
>
> - pg_start_backup_online('blah')
> - backup
> - pg_stop_backup_online()

Editing postgresql.conf for this is ugly. In addition,
pg_start_backup_online would need an additional parameter, the (highly
machine specific) archive_command string. I'd like to see that parameter
untouched in postgresql.conf.

Regards,
Andreas