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rasmus@madhaus.utcs.utoronto.ca
Sat, 7 Sep 1996 09:51:03 -0400 (EDT) 

From: rasmus@madhaus.utcs.utoronto.ca
Date: Sat, 7 Sep 1996 09:51:03 -0400 (EDT)
Subject: [mSQL] Re: 2 simple questions
Message-Id: <ML-2.3.842104263.7349.rasmus@krone.house.mil>

> 2) Had anyone written some kind of "is-msqld-alive" function ?

I run my msqld processes from init so if they die, init automatically
kicks them back up. This is what I have in my /etc/inittab

    m1:234:respawn:/opt/msql/bin/msqld1
    m2:234:respawn:/opt/msql/bin/msqld2

I have hacked up my version of mSQL to allow me to run multiple daemons
out of the same top-level /opt/msql directory.

Running it out of inittab fixes the problem of bringing the daemons back up
when they die, but there is some other weird state they can get into where
they simply stop answering queries. I have the following cron job to test
for this every 5 minutes:

#!/opt/gnu/bin/perl

use Msql;
$mailees = "net-eng\@madhaus.utcs.utoronto.ca";

$ENV{'MSQL_UNIX_PORT'} = "/dev/msql1";
$dbsock = Connect Msql;
if ( !$dbsock ) {
        $sub = "msqld1 is stuck. Restarting it... \n";
        if ( $verbose ) {
                print "$sub";
        }
        &mail_it ("$mailees", "$sub", "");
        system "/etc/init.d/msql kill 1";
} else {
        if ( $verbose ) {
                print "mSQL Daemon 1 is running\n";
        }
}
undef($dbsock);
$ENV{'MSQL_UNIX_PORT'} = "/dev/msql2";

$dbsock = Connect Msql;
if ( !$dbsock ) {
        $sub = "msqld2 is stuck. Restarting it... \n";
        if ( $verbose ) {
                print "$sub";
        }
        &mail_it ("$mailees", "$sub", "");
        system "/etc/init.d/msql kill 2";
} else {
        if ( $verbose ) {
                print "mSQL Daemon 2 is running\n";
        }
}
undef($dbsock);

sub mail_it {
        my ($recipient, $subject, $msg) = @_;
        my $mailer = "/usr/bin/mailx";

        open(MAIL, "|$mailer -s \'$subject\' $recipient");

        print MAIL $msg;
        close MAIL;
}

The above script is obviously using msqlPerl. You could easily do it in
PHP as well. And, chances are you only have 1 daemon to check, so you
could simplify it quite a bit. Note that all I do to restart my daemons
is to kill them off. Since they are running under init, they will be
automatically respawned.

-Rasmus
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