Replacing Docker Cloud

Introducing Redeploy, automatic Docker Hub deployments

Introduction

Last year I wrote a post about automating deployment of your application, all the way from git push to redeploying your application in your environment. It relied on the free version of Docker Cloud, which allowed the use of a single node for free. Of course, the idea was that you should eventually want to scale your deployment, and then you’d need to pay. As long as all you needed was a single node, Docker Cloud and its Bring Your Own Host was powerful, flexible and simple. Life was good.

Unfortunately, cluster management in Docker Cloud is being discontinued. I looked around for other solutions which fulfilled the same requirements. Namely, I wanted something simple, flexible and ideally free. It seems most places nowadays encourages you to simply deploy Kubernetes. Now, I really like the idea of using Kubernetes, but for my hobby projects it’s simply a bit overkill.

Having discarded any prebuilt solutions, I went back to Docker. Their migration guide mentions that the auto-redeploy feature can be emulated with the use of automated builds and a webhook. I found docker-hook, which allows the user to trigger scripts when a webhook is received. Now, this is a good start, and for most users, it’s probably good enough. However, to me there were at least three problems with this solution:

  1. Users have to manually write actions to perform.
  2. It has various bugs in its implementation.
  3. It doesn’t easily allow itself to be used in a container.

So, I went and wrote a better solution.

Introducing Redeploy

Redeploy is a small app that serves a single handler on a configurable endpoint. This endpoint handles Docker webhooks, extracting information and redeploying any configured containers according to their configuration. Its configuration file format is the docker-compose v3 format. Lets look at an example:

version: "3"
services:
    myservice:
        # This must match the repo you've configured
        # the webhook to be sent from.
        # Without a tag, latest is assumed
        image: mydockernamespace/myrepo
        ports:
            - "80:8080"
        restart: always

This configures webhooks from mydockernamespace/myrepo to deploy a docker container with the name myservice, port 80 proxied to 8080 and automatic restarts. It will automatically remove existing containers with the same name.

Conveniently, redeploy itself can be run in a container:

$ docker run --rm -d \
    -v $(pwd)/services.yaml:/services.yaml \
    # Mount the docker socket to allow container control.
    # Alternatively, define $DOCKER_HOST to use a remote docker host.
    -v /var/run/docker.sock:/var/run/docker.sock \
    --name redeploy \
    -p 8555:8555 \
    jfbrandhorst/redeploy --config /services.yaml --path yourconfigureddockerhubpath
Serving on http://0.0.0.0:8555/yourconfigureddockerhubpath

The parameter --path should match the path you’ve configured your Docker webhook for. This should be something unique in order to prevent unauthorized users from restarting your containers!

Conclusion

We’ve introduced redeploy, an app that makes it easy to redeploy your containers automatically straight from a push to your github repo.

If you enjoyed this blog post, have any questions or input, don’t hesitate to contact me on @johanbrandhorst or under jbrandhorst on the Gophers Slack. I’d love to hear your thoughts!

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