#!/bin/bash
#
### BEGIN INIT INFO
# chkconfig: 2345 91 10
# processname: munin-node
# config: /etc/munin/munin-node.conf
# pidfile: /var/run/munin-asyncd.pid
# Provides: munin-asyncd
# Required-Start: $local_fs $remote_fs $network munin-node
# Required-Stop: $local_fs $remote_fs $network
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: Starts and stops munin-asyncd
# Description: munin-asyncd enables asyncronous fetching of
#              metrics from munin-node in a Munin monitoring setup.
### END INIT INFO

ASYNC_BIN=munin-asyncd
PATH=/sbin:/bin:/usr/sbin:/usr/bin
DAEMON=/usr/sbin/${ASYNC_BIN}
PIDFILE=/var/run/munin/${ASYNC_BIN}.pid

is_running () {
	if [ ! -e "$PIDFILE" ]; then
		return 3 # No PID file exists, ${ASYNC_BIN} must not be running
	else
		kill -0 $(cat $PIDFILE) 2> /dev/null
		if [ "$?" -eq "0" ]; then
			return 0 # PID file exists, and PID found in file is in use
		else
			rm $PIDFILE 2> /dev/null
			if [ "$?" -eq "0" ]; then
				return 1 # PID file exists, but no process with the PID was found. Deletion of the PID file was a success
			else
				return 2 # PID file exists, but no process with the PID was found. Deletion of the PID file failed
			fi
		fi
	fi
}

check_root () {
	operation=$1
	if [ "$(id -u)" -ne "0" ]; then
		echo "Root permissions are required in order to perform the \"$operation\" operation."
		exit 4
	fi
}

sanity_check () {
	if [ ! "$(type -p pidof)" ]; then
		echo "The program \"pidof\" is required in order for this script to work properly, and will not run without it."
		exit 1
	fi
	
	if [ ! -d "$(dirname $PIDFILE)" ]; then
		mkdir -p $(dirname $PIDFILE) 2> /dev/null
		if [ "$?" -ne "0" ]; then
			echo "The directory for a PID file is missing ($(dirname $PIDFILE)), and could not be created automatically. Please correct this and try again."
			exit 1
		fi
	fi
	
	if [ ! -x "$DAEMON" ]; then
		echo "${ASYNC_BIN} was expected at $DAEMON, but was not found. Are you sure Munin is correctly installed?"
		exit 5
	fi
}

case $1 in
	start)
		check_root $1
		sanity_check
		
		echo -n "Starting ${ASYNC_BIN} ... "
		
		is_running
		if [ "$?" -eq "0" ]; then
			echo "Already running (PID: $(cat $PIDFILE))."
			exit 0
		fi
		
		$DAEMON > /dev/null 2> /dev/null < /dev/null &
		
		sleep 0.5 # Give ${ASYNC_BIN} time to fail, if it fails
		
		pid=$(pidof -o %PPID -x $DAEMON)
		if [ "$?" -eq "0" ]; then
			echo $pid > $PIDFILE
			echo "Done."
			exit 0
		else
			echo "Start failed for some reason, restarting ${ASYNC_BIN} so you can see why:"
			$DAEMON
			echo
			echo "A \"Connection refused\" message typically is because munin-node is not started prior to ${ASYNC_BIN}."
		fi
	;;
	stop)
		check_root $1
		sanity_check
		
		echo -n "Stopping ${ASYNC_BIN} ... "
		
		# If a PID file is not found, we perform an extra check if ${ASYNC_BIN} still should be running, and if it does, then create a PID file
		if [ ! -e "$PIDFILE" ]; then
			pid=$(pidof -o %PPID -x $DAEMON)
			if [ "$?" -eq "0" ]; then
				echo $pid > $PIDFILE
			fi
		fi
		
		is_running
		if [ "$?" -ne "0" ]; then
			echo "Not running."
			exit 0
		fi
		
		PID=$(cat $PIDFILE)
		kill -15 $PID 2> /dev/null
		HALFSECONDS="0"
		while true; do
			kill -0 $PID 2> /dev/null
			if [ "$?" -eq "1" ]; then
				break
			fi
			sleep 0.5
			HALFSECONDS=$(expr $HALFSECONDS + 1)
			if [ "$HALFSECONDS" -ge "10" ]; then
				kill -9 $PID 2> /dev/null
				echo "Not stopping gracefully, killed!"
				exit 0
			fi
		done
		echo "Done."
		exit 0
	;;
	restart|try-restart|force-reload)
		check_root $1
		sanity_check
		
		$0 stop
		$0 start
		
		exit 0
	;;
	reload)
		echo "The \"reload\" operation is not supported by ${ASYNC_BIN}. You probably want to run \"restart\" instead."
		exit 3
	;;
	status)
		is_running
		return="$?"
		if [ "$return" -eq "0" ]; then
			echo "${ASYNC_BIN} is running (PID: $(cat $PIDFILE))."
			exit 0
		elif [ "$return" -eq "1" ]; then
			echo "${ASYNC_BIN} is not running, but PID file still existed (has been removed now)."
			exit 1
		elif [ "$return" -eq "2" ]; then
			echo "${ASYNC_BIN} is not running, but PID file still exists (could not be removed)."
			exit 1
		elif [ "$return" -eq "3" ]; then
			echo "${ASYNC_BIN} is not running."
			exit 3
		fi
		exit 4
	;;
	*)
		echo "Usage: $0 {start|stop|restart|try-restart|force-reload|reload|status}"
		exit 2
	;;
esac