Re: pg_autovacuum start-script

Okay, here's a rough draft that seems to be working after some simple
testing:

#!/bin/bash

# auto_pg_autovacuum is a utility that can be used in crontab or in init
# scripts to guarantee that pg_autovacuum is running when postgres is
# running.

# Original Author -- Thomas F. O'Connell <tfo(at)sitening(dot)com>
# 2004-08-28

# Assumptions:
# 1. A sane PATH exists that includes pg_ctl and pg_autovacuum.
# 2. pgrep exists on the system and is in PATH.

# Accept an optional PGDATA override.
# Even though -D means daemonize to pg_autovacuum, I thought this
argument
# should be consistent with the PGDATA flags for other postgresql
utilities.
getopts D: opt
[ $opt == ? ] && exit 1
[ $OPTARG ] && PGDATA=$OPTARG

# But if we don't know where to tell pg_ctl to look for status
information,
# then we have to error out.
if [ ! $PGDATA ]; then
echo "PGDATA must be set or specified as an argument to -D";
exit 1;
fi

# Now check to see whether we have a postmaster.
pg_ctl status -D $PGDATA >/dev/null
if [ $? != 0 ]; then
# If we don't, there's no point starting pg_autovacuum.
echo "No postmaster running. Aborting.";
exit 1;
fi

# Now pgrep for an exact match for pg_autovacuum.
pgrep -x pg_autovacuum >/dev/null
if [ $? == 0 ]; then
# If we find something, don't start another one.
echo "pg_autovacuum is already running. Aborting.";
exit 1;
fi

# If we're going to start pg_autovacuum, allow specification of a
logfile
# via -L. Eventually, it would be nice to allow a -o flag or something
# similar to allow any pg_autovacuum options to be passed through.
getopts L: opt
[ $OPTARG ] && LOG="-L $OPTARG"
pg_autovacuum -D $LOG
[ $? == 0 ] && echo "pg_autovacuum successfully started."

This is also available at:

http://www.sitening.com/auto_pg_autovacuum

Eventually, we'll probably create a PostgreSQL utilities section since
I've got some Slony scripts underway, too.

Feedback and comments welcome. I'm not an expert shell scripter, so
best practices tips are especially welcome.

My apologies if this was better posted to HACKERS or a different list.
There's not a contrib list that I know of.

-tfo

On Aug 27, 2004, at 9:33 PM, Matthew T. O'Connor wrote:

> On Fri, 2004-08-27 at 18:09, Thomas F.O'Connell wrote:
>> Hmm. Your last point in particular is one I hadn't considered, yet,
>> largely because it's not relevant to my current problem. For a more
>> generalized solution, though, it should definitely be considered.
>
> Yeah, but as you say, for what you are doing, you probably don't need
> to
> worry about it.
>
>> Does pg_autovacuum currently store the pid of the postmaster against
>> which it's being run? In fact, how does it know against which
>> postmaster it's being run? It doesn't take a database as an argument,
>> does it?
>
> No it doesn't store the PID or anything like that and it doesn't know
> what postmaster it's connecting to, it just connects to what ever
> postmaster is listing to the specified host and port.