Docker: how to ship and share data between containers

Question

I currently have a new server setup where I have Docker running. I use Gitlab CI to create and push new images. I just fail to determine how to deploy/setup my project files and docker images.

To understand my situation, imagine having a PHP project with the following folder structure

• system
• src
• public
• users
• uploads

This is a made-up structure but does reflect the situation where everything except the uploads folder contains PHP scripts.

I could now either go with a separate nginx and php image to run this project, or with a single image containing both these services.

However, this is where my question marks appear. What approach should I take? Because:

1. Creating both a nginx and php image would duplicate my project files over both images, making 2x100mb images. Sidenote: uploads will be mounted from the host system.
2. Creating 1 single image with both services should eliminate the above but comes with other problems, e.g. logging and service management.
3. Creating a data container would also resolve the 2 image sizes and eliminate the problems from point 2, but this is considered bad practices.
4. According to the documentation I am supposed to use data volumes on host to share data between the containers. This would eliminate the data container, but I would than have to have my build process also deploy the project files to the shared data volume, which I think I'd rather not have as this somewhat defeats the purpose of having containers.
5. I also don't see how the previous point (point 4 to be precise) should work/be setup. Would I have a build step in Gitlab that creates a volume and copies all the project files to the volume to mount it at a later time to the php and nginx containers?

Also, I just run docker on my server, as I have no need for solutions like Kubernetes or Rancher.

Answer 1

To manage an application composed by N service I suggesting you to take a look of docker-compose, easy to install, it just manage the docker app for you with some feature like dependency.

To share the data between container volumes is the best solution, if one of the container need to just read the data you can mount the volume as Read Only the volume are host accessible and persistent (until you delete them) so you do not have to create it during the build process. I use it in a django project with nginx as front end, static file are served by nginx from a docker volume where django container wrote them. you can create before start the container the volume by run docker volume create volume_name popolate with your project files and start the containers, manually with docker run or with docker-compose

References: https://docs.docker.com/compose/