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I am quite new to docker and I need some help about distributing my application.

Consider this:

  • I have a pool of physical machines, each of them running the latest version of docker.

  • My "Application A" has several containers. To be clear in this definition, an application would be a database running in a container, 4 messaging containers and a master container. All 6 containers need to communicate between each other. The database, the messaging and etc containers would be the "services".

  • I can also have "Application B", "Application C" and "Application N...", that are slightly different in size and configuration from "Application A". Applications do not communicate between each other and are completely independent.

Requirements:

  • All applications "A,B,C..N" must use the same pool of physical machines.
  • Each service of each application must run in a different physical machine, if needed.
  • You may want to restrict how each service is allocated to each physical machine
  • I need to create applications "on the fly"

My first thought would be to use a docker-compose to define an application and several dockerfiles to define the services inside it. But if I do that, each application would be running in the same docker engine and therefore, the same physical machine.

I have read that you could deploy a docker compose into a docker swarm. In this case, docker swarm would act as a docker engine. However, I could not find any examples on how to do that and I am not sure of the limitations.

My second thought would be to use swarm mode. I would create a swarm, and run services on it. However, I would lose the the concept of "application". There would be a bunch of services thrown into the swarm and I could not manage how each of them communicate with each other.

So, given this problem:

  • Is there any assumption or statement I got wrong?
  • What is the recommended docker tools usage in the scenario?
guilhermecgs
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1 Answers1

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It is possible to use Docker Compose with Docker Swarm Mode (Docker 1.12), but it is currently not completely compatible with it. Have a look at Docker Stacks and Bundles.

In the next version of Docker (1.13) there will also be the new release of Docker Compose v3, which will be compatible with Docker without Docker Compose. This will make it possible to deploy your Docker Compose file like this: docker deploy --compose-file docker-compose.yml AppA

This is currently experimental but works quite fine with Docker 1-13-rc5. (Docker Releases)

A more detailed explanation of this can be found in this article.

For your requirements to have them all run on different hosts, this is possible with defining constraints in the docker service create (or in the Docker Compose v3) (See Docker Service Create - Constraints). But why do you need to have them run on different hosts?

It is possible to limit the CPU and memory usage that each service is able to use with --limit-cpu and --limit-memory.

If you want to play with Docker Swarm Mode you can create a swarm with Docker Machine on your local host. (Attention do not use the old Docker Swarm)

Philip
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