Poor mans service monitoring implemented with crond.

cronic-monitoring

# This cron-file should be deployed to crond:
# $ crontab cronic-monitoring

# Crond will start your services and checks for example every minute, if they are alive.
# Examples:
* * * * * bash -l -c "/abs/path/to/servicename_cronic-monitoring.sh config_a /abs/path/to/servicename_home"
* * * * * bash -l -c "/abs/path/to/servicename_cronic-monitoring.sh config_b /abs/path/to/servicename_home"

servicename_cronic-monitoring.sh

#!/bin/bash

# Arguments

MAIN=`basename "$0"`
CONF=$1
APP_HOME=$2

# Find all process IDs matching this scripts name
# Filter out the PID of this script instance itself (we don't want to see ourself)
pgrep -f "$MAIN.*$CONF" | grep -v ^$$\$ > /dev/null

# If we don't find any other instances of this program, the service is down and has to be started!
if [ $? != 0 ]
then
  echo "[`date`] Starting $MAIN $CONF on `hostname`:$APP_HOME"

  # Make the actual programm a child of this process
  # Because of that, the "servicename" program should be blocking.
  $APP_HOME/bin/servicename >> $APP_HOME/servicename.$CONF.log 2>&1

fi

servicename_status.sh

#!/bin/bash

# Basic idea from
# https://www.digitalocean.com/community/tutorials/how-to-use-a-simple-bash-script-to-restart-server-programs

MAIN="servicename_cronic-monitoring.sh"

# Find the parent process
pgrep -f $MAIN > /dev/null

if [ $? == 0 ]
then
  echo "[`date`] Current PID:"
  pgrep -l -f $MAIN
  echo "[`date`] $MAIN online"
else
  echo "[`date`] $MAIN offline"
fi

servicename_stop.sh

#!/bin/bash

MAIN="servicename_cronic-monitoring.sh"

# Detect the parent pid / process group
PIDS=`pgrep -f $MAIN`

# Kill the process group
if [ ! -z "$PIDS" ]
then
  echo "[`date`] Shutdown process group $MAIN"
  echo "[`date`] Affected PIDs:"
  for PID in $PIDS
  do
    # Prints all PIDs of the process group
    pgrep -l -g $PID
    # Shudown all those processes
    pkill -g $PID
  done
  if [ $? == 0 ]
  then
    echo "[`date`] Shutdown sucess!"
  else
    echo "[`date`] Shutdown failed?"
  fi
else
  echo "[`date`] Nothing to stop"
fi