I have an application war which reads an API implementation jar file to load some data in memory. What I am doing currently is that I COPY that jar inside my "application-war/lib" directory using docker file while generating my applications images.
The downside of this is that whenever the jar needs to be changed; I need to recreate my application war docker image.
Is there a way that I can externalize this jar file location, that I just need to restart of my running pod rather creating a new image each time.
I mean someway if I can give an additional CLASSPATH which my pods container can read while starting up.
Thanks
You are already doing it the right way. The docker image should always be created for each build so you have history as well. It won't be a good practice to change something inside a running pod and restart it somehow.
If you still want to do it that way, you could mount an external volume to your pod and configure your application server to read war file from that location. In this case you will still need access to that volume some other way which allows you to place the file there.
To provide a bit more context. Everything what was said by @Hazim is correct and I fully agree with him about you doing the current build the correct way as it's allows you to see image history and quickly switch if needed.
As for using external files inside your image.
You need to setup a PV - persistent volume, which will be utilized by PVC - persistent volume claim.
A really detailed description with exampled is available on Configure a Pod to Use a PersistentVolume for Storage.
It shows how to create a folder on your node place a file in it which later will be loaded into a pod. You won't be loading that file into a pod but using the path in your Dockerfile to load the .jar file.
If your .jar file is composed of key=value entries you could also use ConfigMap instead of PV. This is nicely explained on a Redis application which you can see here DOCKER / KUBERNETES - CONFIGURE A POD TO USE A CONFIGMAP.
I hope this provides all needed information.