Run Multiple Jar files sequentially (not simultaneously) on “docker run imagename” command

Question

I have two jar files(a.jar and b.jar). b.jar have dependency on a.jar. b.jar can run only after a.jar is up and running. I want to run them via single docker run command. My docker file is like this

# base image is java:8 (ubuntu)
FROM java:8

# add files to image 
ADD a.jar .
ADD b.jar .
ADD start.sh .

# start on run
CMD ["bash", "start.sh"]

start.sh is like this ,

/usr/lib/jvm/java-8-openjdk-amd64/bin/java -jar docker-spring-boot.jar &
/usr/lib/jvm/java-8-openjdk-amd64/bin/java -jar docker-spring-boot-secondary.jar

When i am running docker image both jars are running simultaneously.

When my start.sh is like this,

/usr/lib/jvm/java-8-openjdk-amd64/bin/java -jar docker-spring-boot.jar;
/usr/lib/jvm/java-8-openjdk-amd64/bin/java -jar docker-spring-boot-secondary.jar;

Then only a.jar is running.

I took a help of this How to have two JARs start automatically on "docker run container"

Any help will be appreciated. thanks.

Answer 1

You need to write a script that checks if "a.jar is up and running" and insert it before the second jar call in the following way:

java -jar a.jar &
wait_till_a_jar_is_up_and_running && 
java -jar b.jar

Note: it is important that second time you use && but not & .

None of us knows what "a.jar is up and running" as we don't know what a.jar does. You'll need to implement it yourself (most likely wait-for-it.sh will help you ).

For testing purposes you can try using sleep command:

java -jar a.jar & sleep 10 && java -jar b.jar

Where sleep 10 just waits 10 seconds before running the second jar.