event_watchdog.in 3.85 KB
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#!/usr/bin/perl -w
#
# Copyright (c) 2004-2014 University of Utah and the Flux Group.
# 
# {{{EMULAB-LICENSE
# 
# This file is part of the Emulab network testbed software.
# 
# This file is free software: you can redistribute it and/or modify it
# under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or (at
# your option) any later version.
# 
# This file is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Affero General Public
# License for more details.
# 
# You should have received a copy of the GNU Affero General Public License
# along with this file.  If not, see <http://www.gnu.org/licenses/>.
# 
# }}}
#
use English;
use Getopt::Std;
use POSIX qw(strftime);

sub usage()
{
    print "Usage: $0 [-d]\n";
    exit(1);
}
my $optlist    = "d";
my $debug      = 0;
my $paused     = 0;

#
# Configure variables.
#
my $TB	       = "@prefix@";
my $TBOPS      = "@TBOPSEMAIL@";
my $LOGFILE    = "$TB/log/event_watchdog.log";

# Turn off line buffering on output
$| = 1;

# Only root.
if ($UID != 0) {
    die("*** $0:\n".
	"    Must be root to run this script!\n");
}

#
# Testbed support libs.
#
use lib "@prefix@/lib";
use libtestbed;
use emutil;
use libEmulab;
use event;

# Protos
sub TryEvents();
sub notify($);
sub fatal($);

my %options = ();
if (! getopts($optlist, \%options)) {
    usage();
}
if (defined($options{"d"})) {
    $debug = 1;
}
usage()
    if (@ARGV);

if (CheckDaemonRunning("event_watchdog")) {
    fatal("Not starting another event_watchdog daemon!");
}
# Go to ground.
if (! $debug) {
    if (TBBackGround($LOGFILE)) {
	exit(0);
    }
}
if (MarkDaemonRunning("event_watchdog")) {
    fatal("Could not mark event_watchdog as running!");
}

#
# Delay at startup to allow ops time to boot. Hopefully this
# will prevent too many false alarms at system startup time.
#
sleep(60)
    if (!$debug);

# Loop forever ...
while (1) {
    if (TryEvents() < 0) {
	if (!$paused) {
	    notify("Event server is offline at ".
		   POSIX::strftime("20%y-%m-%d %H:%M:%S", localtime()) . ".\n");
	}
	$paused = 1;
    }
    else {
	if ($paused) {
	    notify("Event server is back online at ".
		   POSIX::strftime("20%y-%m-%d %H:%M:%S", localtime()) .
		   ". Phew!\n");
	}
	$paused = 0;
    }
    sleep(60);
}

#
# Try to connect to event server, protected by a timeout.
#
# Returns: 0 if everything is fine.
#          1 if timed out or otherwise unresponsive.
#
sub TryEvents()
{
    my $URL      = "elvin://event-server";
    my $rval     = 0;

    print "Trying to connect to the event server at $URL\n"
	if ($debug);

    my $childpid = fork();
    if ($childpid) {
	#
	# Parent waits for child to complete.
	#
	local $SIG{ALRM} = sub { kill("USR1", $childpid); };
	alarm 30;
	waitpid($childpid, 0);
	alarm 0;

	# An exit value of 30 is the USR1 signal. 
	if ($?) {
	    if ($? == 30) {
		$rval = -1;
	    }
	    elsif (($? >> 8) == 1) {
		$rval = -1;
	    }
	    # 15 is TERM. Do nothing. 
	    elsif ($? == 15) {
		$rval = 0;
	    }
	    else {
		$rval = -1;
	    }
	}
	else {
	    $rval = 0;
	}
	print "Attempt is returning $rval\n"
	    if ($debug);
	
	return $rval;
    }
    else {
	my $handle = event_register($URL,0);
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	if (!$handle) {
	    print STDERR "Unable to register with event system!\n"
		if ($debug);
	    exit(1);
	}
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	exit(0);
    }
}

sub notify($)
{
    my($mesg) = $_[0];

    print $mesg;

    #
    # Send a message to the testbed list. 
    #
    SENDMAIL($TBOPS,
	     "Event Watchdog Message",
	     $mesg,
	     $TBOPS);
}

sub fatal($)
{
    my ($msg) = @_;

    #
    # Send a message to the testbed list. 
    #
    SENDMAIL($TBOPS,
	     "Event watchdog daemon died",
	     $msg,
	     $TBOPS);

    MarkDaemonStopped("event_watchdog");
    die("*** $0:\n".
	"    $msg\n");
}