Compose Stack in Swarm

Compose in Swarm

Previously, we used the service command, which is similar to the run command, to deploy containers in swarm and adjust scaling. This time, let's learn about stack, which is similar to the compose command. A stack is a unit that groups one or more services together and defines the entire application configuration. Simply think of it as compose that works in swarm (with scaling features included). Another characteristic is that, like compose, services are included in the same network.

First, let's create a network.

$ docker exec -it manager \
docker network create --driver=overlay --attachable test

We created a network named test. Now let's create the stack-compose file. docker-stack.yaml

version: "3"
services:
  flask-echo:
    image: minpeter/flask-echo
    deploy:
      replicas: 3
      placement:
        constraints: [node.role != manager]
    ports:
      - "5000:5000"
    networks:
      - test
  nginx-echo:
    image: minpeter/nginx-echo
    deploy:
      replicas: 3
      placement:
        constraints: [node.role != manager]
    depends_on:
      - flask-echo
    ports:
      - "8080:80"
    networks:
      - test

networks:
  test:
    external: true

Now we need to send the file to the manager container, let's use the docker cp command.

$ docker cp docker-stack.yaml manager:/docker-stack.yaml

Now it's time to deploy the stack.

$ docker exec -it manager \
docker stack deploy -c /docker-stack.yaml echo

Now a simple page that outputs hello, flask! is up on port 8080. Let's check the deployed services.

$ docker exec -it manager \
docker stack services echo

To see how the stack deployed the containers, use the following command.

$ docker exec -it manager \
docker stack ps echo

References

Deploying Docker Containers Using Swarm_2