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