Shell Scripts to start and Stop Spring Boot Applications.

In this post, We will learn about start and stop shell scripts to run Spring Boot applications.

Spring boot applications are easier to build and run. However, there is one small problem. Most of the developers still struggle when it comes to running, stopping, and starting the application in production servers. The traditional applications were deployed on a web container like tomcat which came with a startup.sh and shutdown.sh script. However, this is not available out of the box with spring boot. This article helps you create a simple start and stop script for your spring boot web application.

Start Script (startup.sh)

The startup script for Spring Boot is straightforward. Let's take our hello-world application.

#!/bin/bash
nohup java -jar /path/to/app/hello-world.jar > /path/to/log.txt 2>&1 &
echo $! > /path/to/app/pid.file

To break it down,

• java -jar /path/to/app/hello-world.jar initializes the application.
• > /path/to/log.txt redirects any anything written to STDOUT into the file /path/to/log.txt.
• 2>&1 redirects all errors printed on STDERR to STDOUT. This way all the logs will go to STDOUT which is already redirected to /path/to/log.txt
• & at the end makes the application run in the background.
• echo $! will print the PID of the last command
• The PID is then written to a file using > /path/to/app/pid.file
• nohup lets the java process run in the background even after the user is logged out.

nohup may leave a nohup.out file in working directory when the STDOUT and STDERR is not redirected properly. If that's not what you want, You may want to use disown command to kick-start the script. A sample use case would be disown startup.sh &. But I dislike the way of calling a script with another command.

Stop Script (shutdown.sh)

Comparing to what we have written in the start script, the stop script is pretty simple.

#!/bin/bash
kill $(cat /path/to/app/pid.file)

The shutdown script makes use of the PID file created by the startup script. This allows us to locate and kill the exact process we spawned earlier. The script is pretty simple, and I believe this doesn't need any explanation.

stop and start (restart.sh)

I know that I'm overkilling the topic here. But for the sake of completeness, Here is your restart.sh.

#!/bin/bash
. /path/to/shutdown.sh
. /path/to/startup.sh

stop and start over SSH

You can stop and start your application straight from your local machines if you have a bash client using the following command. I personally use this method most of the time to restart my applications hosted on my servers.

sshpass -p password ssh userid@yourserver '/path/to/restart.sh'

Figure this one out yourself.

There are few points to note though.

• Do not mix the name of the application jar files and paths. Always use canonical paths so its less confusing.
• Do not mix the name of the PID files.
• Your unix login may need necessary permissions to run few of the commands.
• There may be parameters, active profiles and JVM arguments specific to your application. Make sure you configure them in the script.

Conclusion

To conclude, We learned how to write startup.sh, shutdown.sh, and restart.sh to manage the spring boot application process. If you feel like it, you can learn more about converting the application into a WAR file so that you can manage the application via the application server itself.