DockStack – Docker on DevStack on Docker

This project installs DevStack inside a Docker container and integrates Zun, the current OpenStack container project.

Why

A DevStack setup should

1. Not alter the host system
2. Restart clean and fast
3. Allow snapshots
4. Be lightweight
5. Run guest applications fast

The most straight forward option bare metal lacks support for snapshots. It also alters the system heavily, rendering it unusable for other tasks. So it is only suitable for dedicated developer machines. Additionally, the well-known reset workflow of unstack/stack is unreliable, making this solution slow and annoying.

So, get a virtual machine and all of the above problems would be gone! Except for performance of course. Instead of VirtualBox, we could use libvirt with nested-KVM and speed things up. If you already know libvirsh, that may work fine.

Running inside LXD containers might also be an option. They support multiple processes and feel more like a classic VM. Actually, they focus on IaaS [1]. However, an LXD-DevStack setup challenges just as much as on Docker [2], [9].

Also note OpenStack Kolla, which builds individual Docker containers for every project [10].

Not invented here

Running Docker on DevStack actually has been done before [3]. We add the following:

1. Ubuntu 16.04 LTS base image
2. systemd [7]
3. OpenStack Ocata and Pike
4. libvirt/QEMU instance support
5. Zun instead of the deprecated Nova Docker
6. container-adjusted DevStack configuration
7. Network configuration

Containers in OpenStack

Zun [5], OpenStack API for launching and managing containers backed by different technologies including Docker

Nova Docker (deprecated) [4], allows accessing containers via Nova's API, while Zun is not bounded by Nova's API

Nova LXD, pushed by Canonical to promote LXD, OpenStack itself may be installed within LXD with Juju

Magnum (Orchestration), a self-service solution to provision and manage a Kubernetes (or other COEs) cluster

And some more. Get an overview [13].

Quickstart

The Makefile includes a complete Docker lifecycle. Image build and DevStack installation are simply started with

$ git clone https://github.com/janmattfeld/DockStack.git
$ cd DockStack
$ make

This is your host IP address: 172.17.0.2
Horizon is now available at http://172.17.0.2/dashboard
Keystone is serving at http://172.17.0.2/identity/
The default users are: admin and demo
The password: secret

Services are running under systemd unit files.

DevStack Version: pike
OS Version: Ubuntu 16.04 xenial

The first run can take up to 50 minutes, downloading all Ubuntu and Python packages. Subsequent container starts are much faster because of the Docker cache.

Usage

• Enter the main DevStack container directly with make bash.
• Start a Cirros container via Zun with make test.
• Check your installation via Horizon at the displayed address.

Network

Internet access for OpenStack instances

• Edit the public-subnet and enable DHCP with a custom DNS server i. e. 8.8.8.8.

Reaching an OpenStack instance from your host through Docker

1. Add custom rules to the default security group

Ping: Ingress, IPv4, ICMP, Any, 0.0.0.0/0

2. On your host: Route to instances through docker instead of the (here unusable) Open vSwitch/Neutron interface br-ex

$ ip route
172.24.4.0/24 dev br-ex proto kernel scope link src 172.24.4.1

$ sudo ip route del 172.24.4.0/24

$ sudo ip route add 172.24.4.0/24 via 172.17.0.2

$ ip route
172.24.4.0/24 via 172.17.0.2 dev docker0

Zun Troubleshooting

Pulling a new Docker image might fail with 'module' object has no attribute 'get_config_header' because of an old docker-py version [11] [12].

# Remove any Docker SDK artifacts
pip uninstall docker docker-py
rm -rf /usr/local/lib/python2.7/site-packages/docker/auth/
# Get the current version, now just called `docker`
pip install docker
# Make Zun aware of the new Docker library
sudo systemctl restart devstack@zun*

Configuration

Feel free to adjust the file local.conf for your needs [8].

Snapshots

Although a container restart is faster than a complete build, it still takes a few minutes. So for experimenting use

• docker commit to save your running DevStack into the image
• Docker checkpoints [6] (experimental)
• the classic workflow of /devstack/unstack.sh and /devstack/stack.sh

If you really messed it up, make clean followed by make run will set up a fresh DevStack.

Requirements

• Recent Linux (tested on Ubuntu 16.04 LTS and 17.04)
• 4 GB of RAM available for the container
• Docker (tested on 17.06.0-ce)