Tuesday, October 27, 2015

Automated WAR file redeployment in tomcat using a BASH script with the Linux 'at' command

Wouldn't it be nice to schedule a redeployment of your updated web-app during off-peak hours AUTOMATICALLY?

I tried searching for some existing scripts or blogs on how others might have done this, but surprisingly nothing came up. So I'm sharing how I did this from scratch and I'm hoping others will find this useful.

The Bash script

The bash script is responsible for shutting down tomcat, undeploying your webapp, deploying your new web-app and starting up tomcat. The script takes in two arguments.

  • The name of the web-app without the '.war' extension
  • The location of the new version of the web-app
# deploy.sh
# Script to shutdown tomcat and redeploy webapp

#Check the number of arguments
if [ "$#" -ne 2 ]
        echo "Missing arguments: webapp name and WAR file location"
        exit 1

if [ -z "$1" ]
        echo "First argument cannot be empty"
        exit 1

if [ -z "$2" ]
        echo "Second argument cannot be empty"
        exit 1

echo "Tomcat home: $tomcatHome"

# Get the process ID of tomcat
pid=$(ps h -C java -o "%p:%a" | grep catalina | cut -d: -f1)
if [ "$pid" > 0 ]
        echo "Shutting down tomcat PID $pid"

        # Shutdown tomcat
        kill -9 $pid

        # Wait until tomcat is shutdown
        while kill -0 $pid > /dev/null; do sleep 1; done


# remove the old webapp
echo "Removing webapp $1"
mv $tomcatHome/webapps/$1.war $tomcatHome
rm -rf $tomcatHome/webapps/$1

# Copy the new WAR file to the webapps folder
cp $2 $tomcatHome/webapps/$1.war

# Change the permissions
chown tomcat:tomcat $tomcatHome/webapps/$1.war

# Start up tomcat
/etc/init.d/tomcat start

# Finished
echo "redeployed successfully"

An example of how to run the script:
./deploy.sh TaskRequest /home/philip/TaskRequest.war

If you plan on reusing my script, one of the things you'll most likely want to change is the 'tomcatHome' variable and the way I move copies of the old WAR file out of the web-apps folder.

Make sure that you have permissions to execute the bash script:

chmod a+x deploy.sh


 Now that we have our script to execute the redeployment and restart of tomcat, we'll need to schedule a one-time job using linux's 'at' command. As an example, if you want to schedule your redeployment to occur at 9pm tonight, you could use the following command:

at 21:00

This will start a command prompt, where you can now specify what commands or scripts to be executed:

at> /root/deploy.sh TaskRequest /home/philip/TaskRequest.war
CRTL-D will end the prompt

And that's pretty much it. If you want to view the list scheduled jobs you can use the 'atq' command:

[root@apntest1 webapps]# atq
2       2015-10-28 09:30 a root

To view the contents of the scheduled job use 'at -c id ', for example:

[root@apntest1 webapps]# at -c 2
# atrun uid=0 gid=0
# mail   philip 0
umask 22
HOSTNAME=apntest1; export HOSTNAME
SHELL=/bin/bash; export SHELL
OLDPWD=/usr/local/apache-tomcat-7.0.55; export OLDPWD
USER=root; export USER
LS_COLORS=no=00:fi=00:di=00\;34:ln=00\;36:pi=40\;33:so=00\;35:bd=40\;33\;01:cd=40\;33\;01:or=01\;05\;37\;41:mi=01\;05\;37\;41:ex=00\;32:\*.cmd=00\;32:\*.exe=00\;32:\*.com=00\;32:\*.btm=00\;32:\*.bat=00\;32:\*.sh=00\;32:\*.csh=00\;32:\*.tar=00\;31:\*.tgz=00\;31:\*.arj=00\;31:\*.taz=00\;31:\*.lzh=00\;31:\*.zip=00\;31:\*.z=00\;31:\*.Z=00\;31:\*.gz=00\;31:\*.bz2=00\;31:\*.bz=00\;31:\*.tz=00\;31:\*.rpm=00\;31:\*.cpio=00\;31:\*.jpg=00\;35:\*.gif=00\;35:\*.bmp=00\;35:\*.xbm=00\;35:\*.xpm=00\;35:\*.png=00\;35:\*.tif=00\;35:; export LS_COLORS
SUDO_USER=philip; export SUDO_USER
SUDO_UID=501; export SUDO_UID
PATH=/usr/kerberos/sbin:/usr/kerberos/bin:/usr/local/bin:/bin:/usr/bin:/home/philip/bin; export PATH
MAIL=/var/spool/mail/philip; export MAIL
PWD=/usr/local/apache-tomcat-7.0.55/webapps; export PWD
LANG=en_AU; export LANG
SSH_ASKPASS=/usr/libexec/openssh/gnome-ssh-askpass; export SSH_ASKPASS
SHLVL=1; export SHLVL
HOME=/root; export HOME
LOGNAME=root; export LOGNAME
CVS_RSH=ssh; export CVS_RSH
LESSOPEN=\|/usr/bin/lesspipe.sh\ %s; export LESSOPEN
SUDO_GID=501; export SUDO_GID
cd /usr/local/apache\-tomcat\-7\.0\.55/webapps || {
         echo 'Execution directory inaccessible' >&2
         exit 1
${SHELL:-/bin/sh} << `(dd if=/dev/urandom count=200 bs=1 2>/dev/null|LC_ALL=C tr -d -c '[:alnum:]')`

/root/deploy.sh TaskRequest /home/philip/TaskRequest.war

Confirmation email

 Let's take it one step further. If we want to receive email notifications of the automated deployment, we can pipe the output of the script into the mail command as follows:

at 21:00
at> /root/deploy.sh TaskRequest /home/philip/TaskRequest.war | mail -s "Webapp deployment" jo.blo@gmail.com

One liner

If you want to execute the command all in one line without a command prompt, here's an example

echo "/root/deploy.sh TaskRequest /home/philip/TaskRequest.war | mail -s \"Task request redeployed\" jo.blow@gmail.com" | at 19:45

Configuring RHEL to send emails

To install use the following
yum install postfix

If the mail command doesn't work then try installing mailx as well:

# mail
bash: mail: command not found
# yum install mailx

If you're not receiving emails, it's probably because you haven't configured it yet. If you're like me using Red Hat Linux, then here are some basic instructions on how I set it up. Edit the file /etc/postfix/main.cf and set the parameter called relayhost to your smtp server:


Then restart postfix: /etc/init.d/postfix restart
Try testing by sending a test email:

echo "please work" | mail -s "Test email" email@gmail.com

If you didn't receive an email you can debug it by adding the -v flag for verbose output as follows

echo "please work" | mail -v -s "Test email" email@gmail.com
Mail Delivery Status Report will be mailed to root. 

You will get the following response: Mail Delivery Status Report will be mailed to root, here's how to view the message sent to root by using the 'mail' command:

[root@apn-lsrv01 ~]# mail
Heirloom Mail version 12.4 7/29/08.  Type ? for help.
"/var/spool/mail/root": 13 messages 2 new 11 unread
   10 Mail Delivery System  Thu Oct 29 08:09  68/2348  "Mail Delivery Status Report"
   11 Mail Delivery System  Thu Oct 29 08:13  66/2276  "Mail Delivery Status Report"
>N 12 Mail Delivery System  Thu Oct 29 08:28  65/2239  "Mail Delivery Status Report"
 N 13 Mail Delivery System  Thu Oct 29 08:28  65/2239  "Mail Delivery Status Report"

A command prompt will appear asking you which message to open. Enter the ID of the message in this case '13' to see what went wrong with your email.

& 13
Message 13:
From MAILER-DAEMON  Thu Oct 29 08:09:19 2015
Return-Path: <>
X-Original-To: root@blah
Delivered-To: root@blah
Date: Thu, 29 Oct 2015 08:09:19 +1100 (AEDT)
From: MAILER-DAEMON@blah (Mail Delivery System)
Subject: Mail Delivery Status Report
To: root@blah
Auto-Submitted: auto-replied
Content-Type: multipart/report; report-type=delivery-status;
Status: R

Part 1:
Content-Description: Notification
Content-Type: text/plain; charset=us-ascii

This is the mail system at host blah.

Enclosed is the mail delivery report that you requested.

                   The mail system

<someones@email>: delivery temporarily suspended: Host or domain name not
    found. Name service error for name=bad.smtp.server type=AAAA: Host not

In this message I realized, that the relayhost I configured earlier was incorrect. Once I obtained the correct IP address, sending emails started to work.

Use CTRL-D to end the prompt.

Happy to get some feedback on how you might have improved your bash script! Cheers!


Getting the tomcat process PID
How to use the 'at' command
Send emails from linux

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