How to monitor tomcat application and restart if not running?

Question

I have a web application running on Tomcat and would like to have an automated way of monitoring the application to ensure it is running, and if not start/restart tomcat (and also send an email alert). I'd like to do more than just check that Tomcat is running and ensure that a default page from the application can be loaded.

Is there any tool that would be best to do this, aside from writing a shell script and running it as a cron job?

Answer 1

Please look into the Monit utility.

This is a daemon and process-watching tool and can provide the alerts and defined actions that you may need.

A quick example:

check process tomcat with pidfile "/var/run/tomcat/tomcat.pid"
  start program = "/usr/local/tomcat/bin/startup.sh" as uid tomcat gid tomcat
  stop program = "/usr/local/tomcat/bin/shutdown.sh" as uid tomcat gid tomcat
  if failed port 8080 then alert
  if failed port 8080 for 5 cycles then restart

Answer 2

This might help someone!!

If one do not want to use any monitoring tool, then set up an email configurtion in Ubuntu server using mailutils package.

https://rianjs.net/2013/08/send-email-from-linux-server-using-gmail-and-ubuntu-two-factor-authentication

https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-postfix-as-a-send-only-smtp-server-on-ubuntu-14-04

To monitor Tomcat status you can use below script and set up cron job which runs every minute/hour/day according to your needs.

#!/bin/bash

TOMCAT_HOME=/opt/tomcat
PUBLIC_IP=`wget http://ipecho.net/plain -O - -q ; echo`
EMAIL_BODY="Hi Admin,\n\n$PUBLIC_IP Tomcat is down at $(date -d "+330 minutes" +"%Y-%m-%d %T") IST, Please take necessary action.\n\n\nDo not reply to this email as it is auto generated by Ubuntu system\n"

tomcat_pid() {
  echo `ps aux | grep org.apache.catalina.startup.Bootstrap | grep -v grep | awk '{ print $2 }'`
}

start() {
  pid=$(tomcat_pid)
  if [ -n "$pid" ] 
  then
    echo "Tomcat is already running (pid: $pid)"
  else
    # Start tomcat
    echo "Starting tomcat"
    /bin/sh $TOMCAT_HOME/bin/startup.sh
  fi


  return 0
}

pid=$(tomcat_pid)

 if [ -n "$pid" ]
  then
    echo "Tomcat is running with pid: $pid"
    #stop
  else
    echo "Tomcat is not running"
    # send an email alert then start
    echo -e $EMAIL_BODY | mail -s "$PUBLIC_IP Tomcat is down" user@email.com
    echo "Mail sent"
    #remove cache and release memory occupied by heavy processes
    start
  fi
exit 0