Docker-heroku project annotations

Introduction

The goals of the project are:

- Given an app name and release version

- Grab the slug blob

- Unpack

- Map the unpacked slug to a /app inside a container

- Run the container with the commands of a specified process type

Summary

• Project entirely in Go

• Using slug API V3

• Only external dependencies are docker and go-dockerclient

  • (I'm using my own fork because of some fixes needed to work with latest Docker version)

• Go dockerclient lib has some issues, use internal Docker

  • i.e: docker.Config and docker.HostConfig which are tricky to figure.

Installation

go get -v github.com/rsampaio/docker-heroku/...

Usage

docker-heroku -username [email protected] -token a1b2c3d4e5f6 -app heroku-app-name -release 3 -process web

Problems and what I've learned

• Slugs and Releases API where a little tricky to figure how to use version 3

  • "Accept: application/vnc.heroku+json; version=3"

• Go archive/tar and compress/gzip library

• Using the go-dockerclient to mount volumes is kind of a hack due to the internal structs of docker

  volumes := make(map[string]struct{})

  volumes["/app"] = struct{}{}

  err = dClient.StartContainer(container.ID, &docker.HostConfig{Binds: []string{cwd + "/app:/app"}})

• Still prefered go-dockerclient because it can communicate with the default unix socket at /var/run/docker.sock

  • Tried to avoid any docker configuration tweak like listening on tcp port instead of unix domain

• Used a runtime image based on my own project (github.com/rsampaio/dockstep)

  • Basically a dockerfile that install the build deps and clone all buildpacks
  • Could be generated by cedar.sh stack-image

Possible improvements

• Maybe a pre-made image on the docker index on heroku namespace would be nice

  • This image could be built by cedar.sh (or a variation like cedar_docker.sh)

• A progress bar or progress indication while downloading the slug

  • The slug size is already listed on the API

• Use the upcoming ONBUILD feature of docker

  • This feature will run ONBUILD commands when you build a new image based on the image built with ONBUILD commands

• Tag the container for each process type ex: web, worker, etc

• Inject app dir on the container since mapping is only possible for 1 container at a time