toozej/docker-intro repository overview

⁠docker-intro

Introduction to Docker, Docker Compose, and Docker Swarm for a class I'm teaching at Jive

⁠Create Docker image for use in following examples

Build a Docker image with Apache web server hosting the files from the public-html directory.

docker build -t docker-intro-image .

Note that the Docker Hub will automatically build this Docker image thanks to the built in integration between Docker Hub and Github

⁠Dockerfile with Docker run

Now run a container called "docker-intro-run" with the image you've just built

docker run --name docker-intro-run -d -p 80:80 docker-intro-image

Open up a web browser to "http://localhost⁠" (or the IP/hostname of the Docker host on port 80) and you should now see the sample webpage with a meme.

When you're ready for the next method, make sure to stop (and optionally clean up) your Docker container. Be sure to leave the Docker image "docker-intro-image" behind as you'll use it in the other methods.

docker stop docker-intro-run
# optionally
docker kill docker-intro-run

⁠Docker-Compose

Docker Compose uses specially formatted docker-compose.yaml files to store configuration information for a Docker Compose build. In this first example, our docker-compose.yaml is running the exact same image as our Dockerfile example, but is exposing web traffic on port 8080 and passing that through to a load balancer (provided by the ha proxy container) instead of just exposing directly on port 80.

To run the Docker Compose version of our image, do the following:

docker-compose -f docker-compose.yaml up -d

The purpose of setting up our Docker Compose example with a load balancer is so we can scale up our web application (in our example, the Apache container serving public-html files). To do this, use the scale functionality of Docker Compose:

docker-compose scale web=5

Again, check that our web page is up at http://localhost⁠. Also, ensure that your requests to the web page are being properly load balanced across the five containers by watching the logs and refreshing the web page:

docker-compose logs -f

When you're done, shut down your compose build. Note this will remove the "front-tier" network bridge which Docker Compose created as well.

docker-compose down
docker network rm docker-intro-swarm_front-tier

⁠Docker Swarm

The third method of deploying a Docker container is to use Docker Swarm mode. In this example we will be using a single host in order to make the example easier to understand, however in production you will want to use multiple hosts running Docker for a real Swarm. We will also be using the Docker Stack functionality to deploy to the Swarm. See more details at: https://docs.docker.com/engine/swarm/stack-deploy/⁠

Firstly, initialize a single-node Swarm and make sure it's Active:

docker swarm init
docker node ls

Make sure you can start up our web application with Docker Compose, view it in the web browser, then tear it down

docker-compose up -d
docker-compose down

Then deploy our web application to the Docker Swarm as a Service

docker deploy --compose-file docker-compose.yaml docker-intro-swarm
#docker service create --replicas 1 --name docker-intro-swarm docker-intro-image

Note: you may receive errors about "unable to pin image to digest, requested access to the resource is denied" this is a known issue in Docker CE 17.03 and has been fixed. See https://github.com/moby/moby/issues/29205⁠ for details. For now you can ignore the error, as you'll see that your container is running regardless.

Check the docker-intro-swarm service is running with a scale of 1:

docker service inspect --pretty docker-intro-swarm

Then, just as in the Docker Compose example, increase the scale to 5 (and if you're on CE 17.03 ignore any error messages)

docker service scale docker-intro-swarm=5