Using Stack Services Externally

By default, to access services running in a stack from outside, you need to connect through the manager node. However, the echo stack we created in the previous post was configured with the constraints: [node.role != manager] option so it doesn't run on the manager, and since containers are distributed across multiple nodes, we can't use the same approach we used when creating the visualizer service.

Therefore, we'll configure a proxy server that routes traffic from outside the cluster to the inside. Let's use the haproxy image to set up external traffic to go to the nginx containers.

ingress.yaml

version: "3"

services:
  haproxy:
    image: dockercloud/haproxy
    networks:
      - test
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
    deploy:
      mode: global
      placement:
        constraints: [node.role == manager]
    ports:
      - 80:80
      - 1936:1936 # for stats page (basic auth. stats:stats)

networks:
  test:
    external: true

This proxy is a simple one that connects the page on port 8080 to external port 80. Transfer the file to the manager container.

$ docker cp ingress.yaml manager:/ingress.yaml

Deploy the service.

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

You can confirm the service is running with the command below (or you can check using visualizer).

$ docker exec -it manager \
docker service ls

Finally, if you access localhost:8000 in your browser locally, you'll see the message hello, flask!. The reason we access port 8000 even though we forwarded to port 80 in the proxy server is because we set the manager node's port to 8000:80 when we created the cluster containers.

References

Deploying Docker Containers Using Swarm_3 (Using Services from Outside the Swarm Cluster) docker docs