Sharing data between docker containers without making data persistent

Question

Let's say I have a docker-compose file with two containers:

version: "3"
services:
  app:
    image: someimage:fpm-alpine
    volumes:
      - myvolume:/var/www/html

  web:
    image: nginx:alpine
    volumes:
      - myvolume:/var/www/html

volumes:
  myvolume:

The app container contains the application code in the /var/www/html directory which gets updated with each version of the image, so I don't want this directory to be persistent.

Yet I need to share the data with the nginx container. If I use a volume or a host bind the data is persistent and doesn't get updated with a new version. Maybe there is a way to automatically delete a volume whenever I pull a new image? Or a way to share an anonymous volume?

Answer 1

i think its better for you to use anonymous volume

volumes:
  - ./:/var/www/html

Answer 2

You would have to be willing to drop back to docker-compose version 2 and use data containers with the volumes_from directive.

Which is equivalent to --volumes-from on a docker run command.

Answer 3

This should work fine. The problem isn't with docker. You can use volumes to communicate in this way. If you run docker-compose up in a directory with the following compose file:

version: "3"
services:
  one:
    image: ubuntu
    command: sleep 100000
    volumes:
      - vol:/vol
  two:
    image: ubuntu
    command: sleep 100000
    volumes:
      - vol:/vol
volumes:
  vol:

Then, in a 2nd terminal docker exec -it so_one_1 bash (you might have to do a docker ps to find the exact name of the container, it can change). You'll find yourself in a bash container. Change to the /vol directory cd /vol and then echo "wobble" > wibble.txt", then exit` the shell (ctrl-d).

In the same terminal you can then type docker exec -it so_two_1 bash (again, check the names). Just like last time you can cd /vol and type ls -gAlFh you'll see the wibble.txt file we created in the other container. You can even cat wibble.txt to see the contents. It'll be there.

So if the problem isn't docker, what can it be? I think the problem is that nginx isn't seeing the changes on the filesystem. For that, I believe that setting expires -1; inside a location block in the config will actually disable caching completely and may solve the problem (dev only).