hacking.rst

description:	How to hack on Deis including setup instructions

Hacking on Deis

We try to make it simple to hack on Deis. However, there are necessarily several moving pieces and some setup required. We welcome any suggestions for automating or simplifying this process.

If you're just getting into the Deis codebase, look for GitHub issues with the label easy-fix. These are more straightforward or low-risk issues and are a great way to become more familiar with Deis.

Prerequisites

You can develop on any supported platform including your laptop, cloud providers or on bare metal. We strongly recommend a minimum 3-node cluster.

The development workflow requires a Docker Registry that is accessible to you (the developer) and to all of the hosts in your cluster.

You will also need a deisctl client to update images and restart components.

Fork the Repository

To get Deis running for development, first fork the Deis repository, then clone your fork of the repository:

$ git clone git@github.com:<username>/deis.git
$ cd deis
$ export DEIS_DIR=`pwd`  # to use in future commands

Install the Client

In a development environment you'll want to use the latest version of the client. Install its dependencies by using the Makefile and symlinking client/deis.py to deis on your local workstation.

$ cd $DEIS_DIR/client
$ make install
$ sudo ln -fs $DEIS_DIR/client/deis.py /usr/local/bin/deis
$ deis
Usage: deis <command> [<args>...]

Configure SSH Tunneling

To connect to the cluster using deisctl, you must add the private key to ssh-agent. For example, when using Vagrant:

$ ssh-add ~/.vagrant.d/insecure_private_key

Set DEISCTL_TUNNEL so the deisctl client on your workstation can connect to one of the hosts in your cluster:

$ export DEISCTL_TUNNEL=172.17.8.100

Test connectivity using deisctl list:

$ deisctl list

Configure a Docker Registry

The development workflow requires Docker Registry set at the DEV_REGISTRY environment variable. If you're developing locally you can use the dev-registry target to spin up a quick, disposable registry inside a Docker container.

$ make dev-registry

To configure the registry for local Deis development:
    export DEV_REGISTRY=192.168.59.103:5000

Note

For Docker 1.3.1 and later, docker push to this development registry may fail without SSL certificate support. Restart docker with an --insecure-registry flag.

For boot2docker 1.3.1 for example, add EXTRA_ARGS="--insecure-registry 192.168.59.103:5000" to /var/lib/boot2docker/profile and restart docker with sudo /etc/init.d/docker restart.

If you are developing elsewhere, you must set up a registry yourself. Make sure it meets the following requirements:

1. You can push Docker images from your workstation
2. Hosts in the cluster can pull images with the same URL

Note

If the development registry is insecure, you'll have to modify contrib/coreos/user-data.example and whitelist your development registry so the daemons can pull your custom components.

Development Workflow

Deis includes Makefile targets designed to simplify the development workflow. This workflow is typically:

1. Update source code and commit your changes using git
2. Use make -C <component> build to build a new Docker image
3. Use make -C <component> dev-release to push a snapshot release
4. Use make -C <component> restart to restart the component

This can be shortened to a one-liner using the deploy target:

$ make -C controller deploy

You can also use the same tasks on the root Makefile to operate on all components at once. For example, make deploy will build, dev-release, and restart all components on the cluster.

Important

In order to cut a dev-release, you must commit changes using git to increment the SHA used when tagging Docker images

Test Your Changes

Deis ships with a comprehensive suite of automated tests, most written in Go. See :ref:`testing` for instructions on running the tests.

Useful Commands

Once your controller is running, here are some helpful commands.

Tail Logs

$ deisctl journal controller

Rebuild Services from Source

$ make -C controller build push restart

Restart Services

$ make -C controller restart

Django Shell

$ deisctl ssh controller   # SSH into the controller
$ nse deis-controller      # inject yourself into the container
$ cd /app                  # change into the django project root
$ ./manage.py shell        # get a django shell

Have commands other Deis developers might find useful? Send us a PR!

Pull Requests

Please read :ref:`standards`. It contains a checklist of things you should do when proposing a change to Deis.