create a service for an existing container in swarm mode in azure

Question

Note: am new to docker/swarm.

I've created a WordPress/mysql containers in a docker swarm mode running on Azure as per https://docs.docker.com/compose/wordpress/.

The cluster was created as per https://docs.docker.com/docker-for-azure/

here is my dockerfile:

======================
version: '3.3'

services:
   db:
     image: mysql:5.7
     volumes:
       - db_data:/var/lib/mysql
     restart: always
     environment:
       MYSQL_ROOT_PASSWORD: somewordpress
       MYSQL_DATABASE: wordpress
       MYSQL_USER: wordpress
       MYSQL_PASSWORD: wordpress

   wordpress:
     depends_on:
       - db
     image: wordpress:latest
     ports:
       - "8000:80"
     restart: always
     environment:
       WORDPRESS_DB_HOST: db:3306
       WORDPRESS_DB_USER: wordpress
       WORDPRESS_DB_PASSWORD: wordpress
       WORDPRESS_DB_NAME: wordpress
volumes:
    db_data: {}
=======================

as per official documentation, I can publish ports using --published flag, however, I need to know how to include that in Dockerfile.

Running apps You can now start creating containers and services.

$ docker run hello-world

You can run websites too. Ports exposed with --publish are automatically exposed through the platform load balancer:

$ docker service create --name nginx --publish published=80,target=80 nginx

Once up, find the DefaultDNSTarget output in either the AWS or Azure portals to access the site.

Using docker ps, I can see that it is listening on 0.0.0.0:8000->80, however, without a service, it will not automatically create an azure load balance rule to the container.

swarm-manager000000:~/compose$ docker ps
CONTAINER ID        IMAGE                                           COMMAND                  CREATED             STATUS              PORTS                     NAMES
8c94587acd97        wordpress:latest                                "docker-entrypoint.s…"   10 minutes ago      Up 10 minutes       0.0.0.0:8000->80/tcp      compose_wordpress_1
aff61e0022a8        mysql:5.7                                       "docker-entrypoint.s…"   10 minutes ago      Up 10 minutes       3306/tcp, 33060/tcp       compose_db_1
5d2fdb3d75c4        docker4x/l4controller-azure:18.09.2-ce-azure1   "loadbalancer run --…"   2 hours ago         Up 2 hours                                    editions_controller
d5f0a8a91f66        docker4x/meta-azure:18.09.2-ce-azure1           "metaserver -iaas_pr…"   2 hours ago         Up 2 hours          10.0.0.4:9024->8080/tcp   meta-azure
93c6571b6ee6        docker4x/guide-azure:18.09.2-ce-azure1          "/entry.sh"              2 hours ago         Up 2 hours                                    editions_guide
b6cad5676b10        docker4x/logger-azure:18.09.2-ce-azure1         "python /server.py"      2 hours ago         Up 2 hours          0.0.0.0:514->514/udp      editions_logger
d2a74fe21751        docker4x/agent-azure:18.09.2-ce-azure1          "supervisord --confi…"   2 hours ago         Up 2 hours                                    agent
swarm-manager000000:~/compose$

If, for example, I tried to create a service that is mapped to a new image i.e: nginx. this will immediately create an inbound rule in the Azure load balancer.

$ docker service create --name nginx --publish published=80,target=80 nginx

Please advise of how to map the service to the existing WordPress container, or how to update the Dockerfile to create the service and use --published.

Thanks

score 0 · Answer 1 · answered May 13 '19 at 02:48

I have no experience that maps the docker service to an existing container. As I know, it just does the same in the swarm as docker run command. You can take a look at the description of them.

If you really like to map the service to a container, I suggest the AKS than Docker Swarm in Azure, it's more manageable to you for the service and container. It can map the service to the container no matter it's existing one or creates a new one.

For the issue to publish the port. You can achieve it by using the parameter --publish in the docker run command like this:

docker run -d -p 80:80 my_image

Or you can do it in the compose file like this:

ports:
       - "8000:80"

But you cannot publish the port in the Dockerfile, you just can tell the container which port the application listen to by using EXPOSE. Take a look at Expose vs publish: Docker port commands explained simply, then you will know it.

create a service for an existing container in swarm mode in azure

1 Answers1