#!/bin/bash
# Copyright (c) 2005-2023 Pandora FMS
# Author: Sancho Lerena <slerena@artica.es> 2009
# Licence: GPL2
#
# daemon_watchdog
#
# Generic watchdog to detect if a daemon is running. If cannot restart, execute 
# a custom-user defined command to notify daemon is down and continues in
# standby (without notifying / checking) until daemon is alive again.

# Default configuration is for Pandora FMS Server daemon

# =====================================================================
# Configuration begins here. Please use "" if data contain blank spaces

export DAEMON_WATCHDOG=daemon_watchdog
# DAEMON_WATCHDOG: Name of this script. Used to check if its running already

export DAEMON_CHECK="/usr/local/bin/pandora_server /etc/pandora/pandora_server.conf"
# DAEMON_CHECK: Daemon monitored, please use full path and parameters like
#               are shown doing a ps aux of ps -Alf

export DAEMON_RESTART="/etc/init.d/pandora_server restart"
# DAEMON_RESTART: Command to try to restart the daemon

export DAEMON_DEADWAIT=30
# DAEMON_DEADWAIT: Time this script checks after detect that 
#                  daemon is down before to consider is really down. This 

export DAEMON_ALERT="echo 'XXXXX is down. Please do something!' | mail mymail@gmail.com"
# DAEMON_ALERT: Command/Script executed if after detecting daemon is down,
#               and waiting DAEMON_DEADWAIT, and daemon continues down.

export DAEMON_LOOP=7
# DAEMON_LOOP: Interval within daemon_wathdog checks if daemon is alive. 
#              DO NOT use values under 3-5 seconds or could be CPU consuming.
#              NEVER NEVER NEVER use 0 value or gets 100% CPU!.

# Configuration stop here
# =====================================================================

# Check if another instance of this script

RUNNING_CHECK=`ps aux | grep "$DAEMON_WATCHDOG" | grep -v grep |wc -l`
if [ "$RUNNING_CHECK" != "2" ]
then
	echo "Aborting, seems that there are more '$DAEMON_WATCHDOG' running in this system"
	logger $DAEMON_WATCHDOG aborted execution because another watchdog seems to be running
	exit -1
fi


# This value always must be 0 at start. Do not alter
export DAEMON_STANDBY=0 

# This function replace pidof, not working in the same way in different linux distros
function pidof_daemon () (
	# This sets COLUMNS to XXX chars, because if command is run 
	# in a "strech" term, ps aux don't report more than COLUMNS
	# characters and this will not work. 
	COLUMNS=300
	DAEMON_PID=`ps aux | grep "$DAEMON_CHECK" | grep -v grep | tail -1 | awk '{ print $2 }'`
	echo $DAEMON_PID
)

# Main script

if [ ! -f `echo $DAEMON_CHECK | awk '{ print $1 }'` ]
then
	echo "Daemon you want to check is not present in the system. Aborting watchdog"
	exit
fi

while [ 1 ]
do

	DAEMON_PID=`pidof_daemon`
	if [ -z "$DAEMON_PID" ] 
	then
		
		if [ $DAEMON_STANDBY == 0 ]
		then 
		
			# Daemon down, first detection
			# Restart it !
			
			logger $DAEMON_WATCHDOG restarting $DAEMON_CHECK
			$DAEMON_RESTART 2> /dev/null > /dev/null
			
			# Just WAIT another DAEMON_DEADWAIT before consider it DEAD
			
			sleep $DAEMON_DEADWAIT
			DAEMON_PID=`pidof_daemon`
			
			if [ -z "$DAEMON_PID" ]
			then
				
				# Is dead and can't be restarted properly. Execute alert
				
				logger $DAEMON_WATCHDOG $DAEMON_CHECK is dead, alerting !
				$DAEMON_ALERT  2> /dev/null > /dev/null
				
				# Watchdog process puts in STANDBY mode until process get alive again
				logger $DAEMON_WATCHDOG "Entering in Stabdby mode"
				
				DAEMON_STANDBY=1
			fi
		fi
	else
		DAEMON_STANDBY=0
	fi
	
	sleep $DAEMON_LOOP
done