#!/bin/sh
# ----------------------------------------------------------------------------
# /usr/local/nagios/eventhandlers/local_service_restarter - nagios service restarter
#
# Creation   : 2018-01-16 Ansgar Puester
# Last update: $Id$
#
# Copyright (c) 2018 Ansgar Puester, ansgar.puester(at)freenet(dot)de
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
# ----------------------------------------------------------------------------

# Event handler script for restarting a service on the local machine
#
# Note: This script will only restart the service if the service is
#       retried 3 times (in a "soft" state) or if the service somehow
#       manages to fall into a "hard" error state.
#

# ----------------------------------------------------------------------------
# Main
# ----------------------------------------------------------------------------


# set LOGGING to 'yes' to turn on logging to /tmp/local_service_restarter.log
LOGGING='no'

ACT_DATE=$(date)
LOG=/tmp/local_service_restarter.log

[ "$LOGGING" = 'yes' ] && echo "local_service_restarter: $ACT_DATE Parameter: $*" >> $LOG

STATE=$1
TYPE=$2
ATTEMPT=$3
SERVICE=$4

# What state is the service in?
case "$STATE" in
OK)
    # The service just came back up, so don't do anything...
    ;;
WARNING)
    # We don't really care about warning states, since the service is probably still running...
    ;;
UNKNOWN)
    # We don't know what might be causing an unknown error, so don't do anything...
    ;;
CRITICAL)
    # Aha!  The service appears to have a problem - perhaps we should restart the server...
    # Is this a "soft" or a "hard" state?
    case "$TYPE" in

    # We're in a "soft" state, meaning that Nagios is in the middle of retrying the
    # check before it turns into a "hard" state and contacts get notified...
    SOFT)

        # What check attempt are we on?  We don't want to restart the service on the first
        # check, because it may just be a fluke!
        case "$ATTEMPT" in

        # Wait until the check has been tried 3 times before restarting the service.
        # If the check fails on the 4th time (after we restart the service), the state
        # type will turn to "hard" and contacts will be notified of the problem.
        # Hopefully this will restart the service successfully, so the 4th check will
        # result in a "soft" recovery.  If that happens no one gets notified because we
        # fixed the problem!
        3)
            [ "$LOGGING" = 'yes' ] && echo "Restarting service $SERVICE (3rd soft critical state)..." >> $LOG
            # Call the init script to restart the service
            sudo /etc/init.d/$SERVICE restart >> $LOG
            ;;
            esac
        ;;

    # The HTTP service somehow managed to turn into a hard error without getting fixed.
    # It should have been restarted by the code above, but for some reason it didn't.
    # Let's give it one last try, shall we?
    # Note: Contacts have already been notified of a problem with the service at this
    # point (unless you disabled notifications for this service)
    HARD)
        [ "$LOGGING" = 'yes' ] && echo "Restarting service $SERVICE..." >> $LOG
        # Call the init script to restart the service
        sudo /etc/init.d/$SERVICE restart >> $LOG
        ;;
    esac
    ;;
esac

exit 0