Scale the service

Right now, your service is running on a single container. That’s great for now.

You can check how many containers are running using the docker-cloud container ps command.

$ docker-cloud container ps
NAME                   UUID      STATUS     IMAGE                                          RUN COMMAND          EXIT CODE  DEPLOYED     PORTS
web-1                  6c89f20e  ▶ Running  my-username/python-quickstart:latest           python app.py                   1 hour ago   web-1.my-username.cont.dockerapp.io:49162->80/tcp

A single container works just fine for now, but it could be a problem if that container becomes unresponsive. To avoid this, you can scale to more than one container. You do this with the service scale command:

$ docker-cloud service scale web 2

In this example, you can see we’re scaling the service called web to 2 containers.

Run service ps again, and you should now see your service scaling:

$ docker-cloud service ps
NAME                 UUID      STATUS     IMAGE                                          DEPLOYED
web                  68a6fb2c  ⚙ Scaling  my-username/python-quickstart:latest           1 hour ago

If you run container ps you should see multiple containers:

$ docker-cloud container ps
NAME                   UUID      STATUS      IMAGE                                          RUN COMMAND          EXIT CODE  DEPLOYED     PORTS
web-1                  6c89f20e  ▶ Running   my-username/python-quickstart:latest           python app.py                   1 hour ago   web-1.my-username.cont.dockerapp.io:49162->80/tcp
web-2                  ab045c42  ⚙ Starting  my-username/python-quickstart:latest                                                        80/tcp

Containers aren’t assigned a PORT until they are running, so you have to wait until the Service status goes from Scaling to Running to see what port is assigned to them.

$ docker-cloud container ps
NAME                   UUID      STATUS     IMAGE                                          RUN COMMAND          EXIT CODE  DEPLOYED      PORTS
web-1                  6c89f20e  ▶ Running  my-username/python-quickstart:latest           python app.py                   1 hour ago    web-1.my-username.cont.dockerapp.io:49162->80/tcp
web-2                  ab045c42  ▶ Running  my-username/python-quickstart:latest           python app.py                   1 minute ago  web-2.my-username.cont.dockerapp.io:49156->80/tcp

Use either of the URLs from the container ps command to visit one of your service’s containers, either using your browser or curl.

In the example output above, the URL web-1.my-username.cont.dockerapp.io:49162 reaches the web app on the first container, and web-2.my-username.cont.dockerapp.io:49156 reaches the web app on the second container.

If you use curl to visit the pages, you should see something like this:

$ curl web-1.$DOCKER_ID_USER.cont.dockerapp.io:49166
Hello Python Users!</br>Hostname: web-1</br>Counter: Redis Cache not found, counter disabled.%
$ curl web-2.$DOCKER_ID_USER.cont.dockerapp.io:49156
Hello Python Users!</br>Hostname: web-2</br>Counter: Redis Cache not found, counter disabled.%

Congratulations! You now have two containers running in your web service.

What’s Next?

View service logs