Limit useable host resources in Docker compose without swarm

Question

I simply want to limit the resources of some Docker containers in a docker-compose file. The reason is simple: There are multiple apps/services running on the host. So I want to avoid, that a single container can use eg all memory, which harms the other containers.

From the docs I learned, that this can be done using resources . But this is beyond deploy . So I have to write my docker-compose file like the following example:

  php:
    image: php:7-fpm
    restart: always
    volumes:
      - ./www:/www
    deploy:
      resources:
        limits:
          memory: 512M

This gave me the warning:

WARNING: Some services (php) use the 'deploy' key, which will be ignored. Compose does not support deploy configuration - use docker stack deploy to deploy to a swarm.

And that seems to be true: docker stats confirms, the container is able to use all the ram from the host.

The documentation says:

Specify configuration related to the deployment and running of services. This only takes effect when deploying to a swarm with docker stack deploy, and is ignored by docker-compose up and docker-compose run.

But I don't need clustering. It seems that there is no other way to limit resources using a docker composer file. Why is it not possible to specify some kind of memory tag like the start-parameter in docker run does?

Example: docker run --memory=1g $imageName

This works perfectly for a single container. But I can't use this (at least without violating a clean separation of concerns), since I need to use two different containers.

Edit: Temp workaround

I found out, that I'm able to use mem_limit directly after downgrading from version 3 to version 2 (placing version: '2' on top). But we're currently on version 3.1, so this is not a long-time solution. And the docs say, that deploy.resources is the new replacement for v2 tags like mem_limit .

Someday, version 2 is deprecated. So resource management isn't possible any more with the latest versions, at least without having a swarm? Seems a worsening for me, can't belive this...

Answer 1

Since many Docker Compose users have complained about this incompatibility of compose v3 vs v2, the team has developed compatibility mode .

You can retain the same deploy structure that you provided and it will not be ignored, simply by adding the --compatibility flag to the docker-compose command (docker-compose --compatibility up), as explained here . I tested this with version 3.5 and verified with docker stats and can confirm that it works.

Answer 2

You can run the docker daemon in swarm mode on a single host. It will add extra un-needed features like the etcd service discovery but that's all behind the scene.

The Docker documentation has a "note" about it here https://docs.docker.com/engine/swarm/swarm-tutorial/#three-networked-host-machines