You can now use multiple .dockerignore files in Docker.

Firstly you need to enable BuildKit mode; this is done either by setting:

export DOCKER_BUILDKIT=1

or by adding this configuration:

{ "features": { "buildkit": true } }

to the Docker daemon configuration in ~/.docker/daemon.json and restarting the daemon. This will be enabled by default in future.

You also need to prefix the name of your .dockerignore file with the Dockerfile name.

So if your Dockerfile is called OneApp.Dockerfile the ignore file needs to be called OneApp.Dockerfile.dockerignore.

All taken from this comment: https://github.com/moby/moby/issues/12886#issuecomment-480575928

For reference, I was able to get this working the way I wanted by using docker buildx bake along with an hcl configuration just like the blog post describes near the end. I'm still not sure whether this is possible via command line args with --build-context because of the way .dockerignore files are loaded. In any case, I'm happy with the solution we settled on.

Docker 19.03 shipped a solution for this.

The Docker client tries to load <dockerfile-name>.dockerignore first and then falls back to .dockerignore if it can't be found. So docker build -f Dockerfile.foo . first tries to load Dockerfile.foo.dockerignore.

Setting the DOCKER_BUILDKIT=1 environment variable is currently required to use this feature. This flag can be used with docker compose since 1.25.0-rc3 by also specifying COMPOSE_DOCKER_CLI_BUILD=1.

See also comment0, comment1, comment2

from Mugen comment, please note

the custom dockerignore should be in the same directory as the Dockerfile and not in root context directory like the original .dockerignore

i.e. when calling

export DOCKER_BUILDKIT=1
docker build -f /path/to/custom.Dockerfile

your .dockerignore file should be at

/path/to/custom.Dockerfile.dockerignore

That depends on what your docker build command looks like. If you perform a docker build -f app/Dockerfile . from the parent directory where the .dockerignore file is then it would include the .dockerignore but if you are in either app or server and run docker build ., it wouldn't be included as .dockerignore isn't in the build context.

In a simple way no.

The .dockerignore file is used to filter what will be used in the build before even reading the Dockerfile.

The docker daemon does not see your build folder, when the build starts, all the files in the context build folder are compressed (or just packed) and send to the daemon and only then it will read your Dockerfile to build the container with the files it received.

More content about .dockerignore: https://docs.docker.com/engine/reference/builder/#/dockerignore-file

When you build an image, you send the Docker daemon a build context; in your Compose setup this is the directory named in the build: { context: } setting. The .dockerignore file must be in that exact directory and nowhere else. Its actual effect is to cause files to be excluded from the build context, which can result in a faster build sequence.

The build context's other important effect is that all Dockerfile COPY directives are considered relative to that directory; you cannot COPY from parent or sibling directories. So if files are shared between projects, you must set the context directory to some ancestor directory of all of the files that will be included, and COPY directives will be relative to that directory (even if the Dockerfiles are in per-project directories). See also How to include files outside of Docker's build context?

If your projects are completely separate: maybe there's a front-end and a back-end project, or in your case a producer and a consumer that share a message format but not any actual code. Then in this case:

• Put a Dockerfile, named exactly Dockerfile, in each project subdirectory
• Put a .dockerignore file in each project subdirectory (it cannot be in the parent directory)
• COPY directives are relative to the project subdirectory

  COPY requirements.txt ./
  

• In the Compose file, you can use the shorthand build: directory syntax, since you have the standard (default) dockerfile: name

  version: '3.8'
  services:
     producer:
       build: ./python_producer
       environment:
         - RABBITMQ_HOST=rabbitmq
     consumer:
       build: ./python_consumer
       environment:
         - RABBITMQ_HOST=rabbitmq
     rabbitmq:
       image: rabbitmq:3
       hostname: rabbitmq # RabbitMQ is very unusual in needing to set this
  

If your projects share code or other files: in your example maybe you define Python data structures for the message format in shared code. This in this case:

• Put a Dockerfile, named exactly Dockerfile, in each project subdirectory
• Put a single .dockerignore file in the project root
• COPY directives are relative to the project root directory

  COPY python_producer/requirements.txt ./
  

• In the Compose file you need to specify context: . and dockerfile: pointing at a per-component Dockerfile

  version: '3.8'
  services:
     producer:
       build:
         context: .
         dockerfile: python_producer/Dockerfile
       environment:
         - RABBITMQ_HOST=rabbitmq
     consumer:
       build:
         context: .
         dockerfile: python_consumer/Dockerfile
       environment:
         - RABBITMQ_HOST=rabbitmq
     rabbitmq:
       image: rabbitmq:3
       hostname: rabbitmq # RabbitMQ is very unusual in needing to set this