Re: Config reload/restart preview

On Thu, Jun 20, 2013 at 4:34 PM, Thom Brown <thom@linux.com> wrote:

Hi,

I've noticed that there's no easy way of checking which settings will change if the config is reloaded, and I think not being able to do this can cause some unfortunate problems.

For example, a customer went to change their configuration, just setting log_autovacuum_min_duration to about 20 seconds, and reloaded the server.  However, the log file swelled to over 5GB in size before they realised something was wrong, and then reverted the change.  It transpired that the reload also pulled in a log_statements change from 'ddl' to 'all' that someone must have changed at some point without applying it.

Should we have a way of previewing changes that would be applied if we reloaded/restarted the server?

For example:

pg_ctl previewconfig

SIGHUP: log_statements will change from 'ddl' to 'all'

SIGHUP: log_vacuum_min_duration will change from -1 to 20000

POSTMASTER: fsync will change from 'on' to 'off'

I'm not proposing this specifically, but something that would provide such information.

May be we can have a nice little utility which can show configuration diff between two running servers, or a running server and its modified conf file ?