Example: Docker

Source: https://porter.sh/src/examples/docker

The getporter/whalesay bundle demonstrates how to use Docker inside a bundle!

Sometimes you need a hammer, and that hammer happens to be a whale 🐳. We all use containers as part of our pipeline: building images, running a one-off command in a utility container, spinning up a test environment to verify your application, or even more creative tasks that you have already containerized. Well now you can reuse all that hard work and logic from within your bundles!

Let’s walk through using my favorite container, docker/whalesay, in a bundle.

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Author the bundle

Writing a bundle that uses Docker has a few steps:

• Require Docker
• Install Docker
• Use Docker

Here’s the full working example whalesay bundle for you to follow along with.

Require Docker

The user running the bundle, and Porter, needs to know that this bundle requires the local Docker daemon connected to the bundle. We have added a new section to porter.yaml for required extensions, and defined a new prototype extension that says that the bundle requires access to a Docker daemon:

required:
- docker

Optionally you can include that you also want the bundle to be run with --privileged which is intended for docker-in-docker scenarios:

required:
- docker:
    privileged: true

Install Docker

You can include the Docker CLI in your bundle by using the docker mixin.

mixins:
  - docker

You can then use the respective CLIs through the mixin:

install:
- docker:
    description: "Run my container"
    run:
      image: hello-world
      rm: true

Use Docker

In my porter.yaml, I can use the docker mixin to execute docker commands in my bundle:

After I have tested the bundle, I used porter publish to push it up to getporter/whalesay:v0.1.2.

Run that bundle

Now that the bundle is ready to use, the user running the bundle needs to give the bundle elevated permission with the Allow Docker Host Access setting. This is because giving a container access to the host’s Docker socket, or running a container with --privileged, has security implications for the underlying host, and should only be given to trusted containers, or in this case trusted bundles.

Let the whales speak!

$ porter install --reference getporter/whalesay:v0.1.2 --allow-docker-host-access
installing whalesay...
executing install action from whalesay (bundle instance: whalesay)
Install Hello World
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execution completed successfully!

I can set the flag --allow-docker-host-access with the PORTER_ALLOW_DOCKER_HOST_ACCESS environment variable so that I don’t have to specify it for every command.

export PORTER_ALLOW_DOCKER_HOST_ACCESS=true

Now let’s see what else we can do with whalesay:

$ porter invoke whalesay --action=say --param 'msg=try it yourself!'
invoking custom action say on whalesay...
executing say action from whalesay (bundle instance: whalesay)
Say Something
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execution completed successfully!