CODEWITHSUNDEEP
dockerdocker-compose
Mijamo
Mijamo

Reputation: 3516

Docker compose - access data from container A in container B

Here is my problem:

I have a container A (Node.js) and a container B (nginx). In the Dockerfile of container A, I build several files from the sources, as they are needed to run the server into a folder named build. I want to access this folder from container B to serve the static files.

The purpose is to have a simple workflow were you could just git clone the repo with the sources and run docker-compose up --build and everything is running. In this scenario, the host does not have the software needed to build the file, so the build must happen INSIDE the docker container.

My first attempt that almost work was the following:

version: "2"
services:
    nginx:
        volumes_from:
            - node

    node:
        volumes:
        - /code/build

When I first built docker compose build & up everything seemed to work fine, the container is created from the container A with the build files inside it and the container B can access them as expected.

However, the issue happens when the sources are updated. When it happens, the new build files do not replace the old one inside the container because the existing container seems to have the priority. So after the first time I always have old files for both container A and B.

I investigated a way to force the volume to be recreated from scratch everytime I run docker-compose build but did not find anything. The only thing I found would be to use docker-compose stop && docker-compose rm but it seems to be a bit hacky to do that everytime and in addition it leads to a quite long downtime compared to just replace existing container with new version with docker-compose up.

Is there any proper solution to acomplish what I am trying to achieve?

Upvotes: 2

Views: 813

Answers (1)

BMitch
BMitch

Reputation: 263846

I'd redo the workflow, use a named volume that's mounted in multiple containers, and one of those containers is an updater that has the application build environment. Then on launch, the updater pulls the latest from git and updates the shared volume as part of its CMD or ENTRYPOINT.

Your compose file would look similar to:

version: "2"
volumes:
    build:
       driver: local

services:
    nginx:
        volumes:
        - build:/code/build

    updater:
        volumes:
        - build:/code/build

Then on any changes, you can run a docker-compose run updater and it will push the latest changes to your volume where nginx can use it without ever stopping your other containers. Since it's a batch job that exits, even a docker-compose up would launch the updater again.

Upvotes: 1

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