[Pkg-postgresql-public] Bug#739276: postgresql: Put pgstat in /var/run

[Christian Tacke]

On Fri, Mar 07, 2014 at 13:40:53 +0100, Christoph Berg wrote:
> Re: Martin Pitt 2014-03-07 <20140307090805.GA23354 at piware.de>
> > I think configuring a tmpfs dir by default is a good idea, thanks for
> > pointing that out.
> 
> +1.
> 
> > > === modified file 'createcluster.conf'
> > > --- createcluster.conf	2013-04-12 12:32:08 +0000
> > > +++ createcluster.conf	2014-02-17 11:26:47 +0000
> > > @@ -23,3 +23,6 @@
> > >  # All other options are copied into the new cluster's postgresql.conf
> > >  
> > >  log_line_prefix = '%%t '
> > > +
> > > +# Starting at version 8.4 one can move the pg_stat_tmp dir
> > > +stats_temp_directory = '/var/run/postgresql/%v-%c_stat_tmp'
> > 
> > Note that this is a little too simplistic. This directory is only
> > writable to clusters owned by postgres. While that is the default, you
> > can assign any other owner, and you can even call pg_createcluster as
> > a normal user and put everything into your $HOME; in those cases,
> > /tmp/ will be used for the Unix socket, and we can't use
> > /var/run/postgresql/.
> 
> pg_createcluster will still want to write to /etc/postgresql which is
> owned by postgres, so the stats_temp_directory doesn't make the
> situation worse.
> 
> > One idea is to add a new "%s" macro to the evaluation of
> > createcluster.conf which expands to the used socket dir, and set
> > stats_temp_directory = '%s/%v-%c_stat_tmp'. That's a little more
> > complex, but always ought to work since we know that the socket dir is
> > writable.
> 
> For non-postgres clusters, the socket dir will be /tmp, which isn't a
> tmpfs at least on my machine (I forgot which default Debian really
> decided on in that flameware).
> 
> > A simpler solution might be to use /var/run/lock/ instead, which is
> > world-writable (same permissions as /tmp/). It's just a bit of an
> > abuse as these are not really lock files.
> 
> /var/run/lock wouldn't work because it's too small (5120k here).
> 
> > A third option would be to not put this into createcluster.conf, but
> > dynamically set it up in pg_createcluster; i. e. only postgres-owned
> > clusters would configure this (more specifically, add the option if
> > /var/run/postgresql is writable for the owner, so that admins could
> > put other users into the postgres group).
> 
> ... or mount a new tmpfs, but that would require root.
> 
> I think this, and the %s idea are too complex for the resulting
> effect. Imho what Christian proposed is just the right approach,
> people can still disable it in createcluster.conf.
> 
> Christoph
> -- 
> cb at df7cb.de | http://www.df7cb.de/
> 

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