Mount a volume in docker-compose conditionally

Question

I have a docker-compose.yml configuration. In one of the containers there is a Tomcat server and it has some default .war file deployed in we

Answer 1

Instead of (not) mounting a volume commenting out that line, I would use https://docs.docker.com/compose/extends/#example-use-case to run a service extension that specifies a volume.

I do this to tackle two different problems:

• I don't specify a volume when the docker image is meant to run in production and has all the necessary files bundled in it.
• I specify a volume during development, to check live changes.

Answer 2

Since extend has been removed in version 3 there's a new way of overriding settings by providing multiple -f params where the next file extends the previous config

The docs are mixed between versions https://docs.docker.com/compose/extends/#multiple-compose-files

i.e. to run in development mode

docker-compose -f docker-compose.yml -f docker-compose.dev.yml

Where docker-compose.yml contains the full config and docker-compose.dev.yml only adds a volume

services:
  serviceA:
    volumes:
      -.:/usr/local/abc/service

Answer 3

Let's say that the .war filename is "app.war"... you could overwrite it using a env variable like this:

volumes:
 - ./application/webapps/${APPLICATION_ENV}.war:/usr/local/tomcat/webapps/app.war

Then when you need to run a different war file just change the APPPLICATION_ENV value to the one you need to run and restart the container.

I don't think docker-compose does have "conditional volumes", but that way you could change the app.war according with your environment.

Other way would be running a script after the docker-compose up/start to overwrite it, and do it only when needed, like:

docker-compose exec your-container-name cp /a/volume/path/app.war /usr/local/tomcat/webapps/app.war