Deploy to the Docker platform

Docker provides tooling and a platform to manage the lifecycle of lightweight virtualization packages, known as containers. In this guide, we will cover the steps necessary to Dockerize a Kitura application. This includes how to build the Docker image and how to create the container instance from that image.

A full description of the Docker platform can be found on the Docker website, including installation instructions. This guide is based on the two Dockerfiles generated by the Kitura CLI's kitura init command.

Step 1: Build compile image

As the Swift compiler is large and not required for running compiled Kitura applications, the Docker images for application compilation and runtime are separated into a build image and a run image. The kitura init command supports this two step build process by generating two Dockerfiles for your Kitura project:

  • Dockerfile-tools: building this Dockerfile produces a Docker image containing everything needed to compile your Kitura application. Running the image will compile your Kitura application.
  • Dockerfile: building this Dockerfile produces a Docker image containing your compiled application. Running the image will run your application.

We first need to build the compile image:

docker build -t myapp-build -f Dockerfile-tools .

The above command builds a Docker image called "myapp-build" using the generated Dockerfile-tools file. We will use this image to compile our Kitura application.

Step 2: Compile application code

Using the image we've just built, we can compile the application code with the following command:

docker run -v $PWD:/swift-project -w /swift-project myapp-build /swift-utils/ build release

The Docker run command takes the '-v' option which maps the current working directory on the host to the '/swift-project' directory on the Docker container. The -w option sets working directory inside the container. We then tell Docker to create a container using the myapp-build tag name from the image we created earlier. Finally we invoke the utility script that is located in the container at /swift-utils/ to build in release mode. The file can be viewed here.

Step 3: Build the run image

Now that we have compiled our Kitura application we can now build the Docker runtime image, with the following command.

docker build -t myapp-run .

This command builds a Docker image which is tagged "myapp-run" using the generated Dockerfile file. The newly built Docker image contains your compiled Kitura application and the necessary Swift runtime libraries.

Step 4: Check the image is available

Docker provides a command to list your local images:

docker image ls

This command lists the Docker images available in your local repository, which will include your recently built image tagged "myapp-run".

Step 5: Start the Docker container

Now that we have an image that contains our Kitura application, we just need to run an instance of the image:

docker run -p 8080:8080 -it myapp-run

The above Docker run command uses the -p flag to publish port 8080 to the host interfaces. It then runs a container from the myapp-run image in interactive mode. You can see your container is running with the following command:

docker container ps -a

Since we exposed our ports, we should then be able to navigate to: localhost:8080 to view our server.