dyndns

#!/bin/bash

### BEGIN INIT INFO
# Provides: dyndns
# Required-Start:    $network $remote_fs $local_fs
# Required-Stop:     $network $remote_fs $local_fs
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: forever-service startup script for dyndns
# Description: forever-service startup script for node script based service dyndns, uses forever to start the service
### END INIT INFO


#	CLI node /usr/local/bin/forever-service install dyndns --script app.js
#	Working Directory /home/pi/bin/cloudflaredyndns

#Setup Environment variables:
APP_PATH="/home/pi/bin/cloudflaredyndns"

# Check if any of $pid (could be plural) are running
LOGFILE="/var/log/dyndns.log"

LOCKFILE="/var/lock/dyndns"

# introduce some gaps between restarts and throttle continous restarts
MIN_UPTIME="5000"
SPIN_SLEEP_TIME="2000"

# kill signal: Since default needs to be SIGTERM, it is important that services gracefully shutdown,
# specially if they are doing transactions or other work which should not be interuppted in between
# for exceptional situation where you dont care about abrupt shutdown, SIGKILL should be used
KILL_SIGNAL="SIGTERM"

# Wait time afer with SIGKILL will be sent to the process, in case SIGTERM is not fully finished
# This is required since when we use SIGTERM, some times if there is problem in code, it might take lot of time for process to exit
# or process may never exit, in such siutation we have to forcebly kill it so that shutdown or service restart can be done appropriately
# this wait time is in millisecond
KILLWAITTIME=5000

killtree() {
    local _pid=$1
    local _sig=${2:--TERM}
    kill -stop ${_pid} # needed to stop quickly forking parent from producing children between child killing and parent killing
    for _child in $(ps -o pid --no-headers --ppid ${_pid}); do
        killtree ${_child} ${_sig}
    done
    kill -${_sig} ${_pid}
}

checkpidexists() {
	[ -d "/proc/$1" ] && return 0
	return 1
}



start() {
	#this is to ensure forever is able to find out the correct root every time
	export FOREVER_ROOT=/root/.forever
    
	STATUS=$(/usr/local/bin/forever --plain list | sed 's/data:\(\s*\[[0-9]*\]\s*\(dyndns\)\s.*\)/\2-status:\1/;tx;d;:x')
	
	if ! [ -z "$STATUS" ]; then
		echo "Service dyndns already running"
		return 0
	fi

	echo  "Starting dyndns"



	
	# move to the directory from where the inital forever script was launched so that even if it is relative it works as expected
	cd $APP_PATH

	

	/usr/local/bin/forever \
	-a \
	-l $LOGFILE \
	--minUptime $MIN_UPTIME \
	--spinSleepTime $SPIN_SLEEP_TIME \
	--killSignal $KILL_SIGNAL \
	 \
	--uid dyndns \
	start app.js  2>&1 >/dev/null
	
	RETVAL=$?

 	[ $RETVAL = 0 ] && touch $LOCKFILE
 	return $RETVAL
}	

stop() {
	#this is to ensure forever is able to find out the correct root every time
	export FOREVER_ROOT=/root/.forever

	echo -n "Shutting down dyndns: "

    
	STATUS=$(/usr/local/bin/forever --plain list | sed 's/data:\(\s*\[[0-9]*\]\s*\(dyndns\)\s.*\)/\2-status:\1/;tx;d;:x')
	
	if [ -z "$STATUS" ]; then
		echo "Not running"
		return 0
	fi

	# PID=$(<$PIDFILE) - Changed to detection based on actual PID from forever, sicne due to watchDirectory pid could dynamically change
    
	PID=$(/usr/local/bin/forever --plain list | sed -n -e '/data:\s*\[[0-9]*\]\s\(dyndns\)\s/p' | awk '{print $7}')
	

	if [ -z "$PID" ]; then
		echo "Could not get pid"
		return 0
	fi

	#run in background, since recent changes in forever, now blocks stop call with SIGTERM is finished
	#but we want to wait till some time and forcibly kill after elapsed time
	#without background script, we could be waiting forever
	
	/usr/local/bin/forever stop dyndns 2>&1 >/dev/null &
	

	CURRENTWAITTIME=$KILLWAITTIME
	# wait for some time before forcefully killing the process
	while [ $CURRENTWAITTIME -gt 0 ]; do
		#check if the process is still running
		checkpidexists $PID
		if [ $? -ne 0 ]; then
			# if not running we can break, since no more wait is needed, service is stopped
			echo "Successful"
			break
		fi
		
	 	sleep 1
	 	CURRENTWAITTIME=$(( $CURRENTWAITTIME - 1000))
	 	
	done
	checkpidexists $PID
	if [  $? -eq 0  ]; then
		killtree $PID 9
		echo 'Forced shutdown'
	fi

	rm -f $PIDFILE 2>&1 >/dev/null
	rm -f $LOCKFILE 2>&1 >/dev/null
	return 0

}

status() {
	#this is to ensure forever is able to find out the correct root every time
	export FOREVER_ROOT=/root/.forever

    
	STATUS=$(/usr/local/bin/forever --plain list | sed 's/data:\(\s*\[[0-9]*\]\s*\(dyndns\)\s.*\)/\2-status:\1/;tx;d;:x')
	
	if [ -z "$STATUS" ]; then
		echo "dyndns is not running"
		RETVAL=3
	else		
		echo $STATUS
		RETVAL=0
	fi
	return $RETVAL
}

case "$1" in
    start)
	start
	;;
    stop)
	stop
	;;
    status)
	status
	;;
    restart)
    	stop
	start
	;;
    *)
	echo "Usage: <servicename> {start|stop|status|restart}"
	exit 1
	;;
esac
exit $?