OpenStack Newton and LXD

Background

This post is about deploying a minimal OpenStack newton cluster atop LXD on a single machine. Most of what is mentioned here is based on OpenStack on LXD.

Introduction

The rationale behind using LXD is simplicity and feasibility: it doesn’t require more than one x86_64 server with 8 CPU cores, 64GB of RAM and a SSD drive large enough to perform an all-in-one deployment of OpenStack Newton.

According to Canonical, “LXD is a pure-container hypervisor that runs unmodified Linux guest operating systems with VM-style operations at incredible speed and density.”. Instead of using pure virtual machines to run the different OpenStack components, LXD is used which allows for higher “machine” (container) density. In practice, an LXD container behaves pretty much like a virtual or baremetal machine.

For all purposes, I will be using Ubuntu 16.04.02 for this experiment on a 128GB machine with 12 CPU cores and 4x240GB SSD drives configured using software RAID0. For increased performance and efficiency ZFS is also used (dedicated partition separate from the base OS) as a backing store for LXD.

Preparation

$ sudo add-apt-repository ppa:juju/devel
$ sudo add-apt-repository ppa:ubuntu-lxc/lxd-stable
$ sudo apt update
$ sudo apt install \
    juju lxd zfsutils-linux squid-deb-proxy \
    python-novaclient python-keystoneclient \
    python-glanceclient python-neutronclient \
    python-openstackclient curl
$ git clone https://github.com/falfaro/openstack-on-lxd.git

It is important to run all the following commands inside the openstack-on-lxd directory where the Git repository has been cloned locally.

LXD set up
$ sudo lxd init

The relevant part here is the network configuration. IPv6 is not properly supported by Juju so make sure to not enable. For IPv4 use the 10.0.8.0/24 subnet and assign the 10.0.8.1 IPv4 address for LXD itself. The DHCP range could be something like 10.0.8.2 to 10.0.8.200.

NOTE: Having LXD listen on the network is also an option for remotely managing LXD, but beware of security issues when exposing it over a public network. Using ZFS (or btrfs) should also increase performance and efficiency (e.g. copy-on-write shall save disk space by prevent duplicate bits from all the containers running the same base image).

Using an MTU of 9000 for container interfaces will likely increase performance:

$ lxc profile device set default eth0 mtu 9000

Next step is to spawn an LXC container for testing purposes:

$ lxc launch ubuntu-daily:xenial openstack
$ lxc exec openstack bash
# exit

An specific LXC profile named juju-default will be used when deploying OpenStack. In particular this profile allows for nesting LXD (required by nova-compute), allows running privileged containers, and preloads certain kernel modules required inside OpenStack containers.

$ lxc profile create juju-default 2>/dev/null || \
  echo "juju-default profile already exists"
$ cat lxd-profile.yaml | lxc profile edit juju-default
Bootstrap Juju controller
$ juju bootstrap --config config.yaml localhost lxd
Deploy OpenStack
$ juju deploy bundle-newton-novalxd.yaml
$ watch juju status
Testing

After Juju has finished deploying OpenStack, make sure there is a file named novarc in the current directory. This file is required to be sourced in order to use the OpenStack CLI:

$ source novarc
$ openstack catalog list
$ nova service-list
$ neutron agent-list
$ cinder service-list

Create Nova flavors:

$ openstack flavor create --public \
    --ram   512 --disk  1 --ephemeral  0 --vcpus 1 m1.tiny
$ openstack flavor create --public \
    --ram  1024 --disk 20 --ephemeral 40 --vcpus 1 m1.small
$ openstack flavor create --public \
    --ram  2048 --disk 40 --ephemeral 40 --vcpus 2 m1.medium
$ openstack flavor create --public \
    --ram  8192 --disk 40 --ephemeral 40 --vcpus 4 m1.large
$ openstack flavor create --public \
    --ram 16384 --disk 80 --ephemeral 40 --vcpus 8 m1.xlarge

Add the typical SSH key:

$ openstack keypair create --public-key ~/.ssh/id_rsa.pub mykey

Create a Neutron external network and a virtual network for testing:

$ ./neutron-ext-net \
    -g 10.0.8.1 -c 10.0.8.0/24 \
    -f 10.0.8.201:10.0.8.254 ext_net
$ ./neutron-tenant-net \
    -t admin -r provider-router \
    -N 10.0.8.1 internal 192.168.20.0/24

CAVEAT: Nova/LXD does not support use of QCOW2 images in Glance. Instead one has to use RAW images. For example:

$ curl http://cloud-images.ubuntu.com/xenial/current/xenial-server-cloudimg-amd64-root.tar.gz | \
  glance image-create --name xenial --disk-format raw --container-format bare

Then:

$ openstack server create \
    --image xenial --flavor m1.tiny --key-name mykey --wait \
    --nic net-id=$(neutron net-list | grep internal | awk '{ print $2 }') \
    openstack-on-lxd-ftw

NOTE: For reasons I yet do not understand, one can’t use a flavor other than m1.tiny. Reason is that this flavor is the only one that does not request any ephemeral disk. As soon as ephemeral disk is requested, the LXD subsystem inside the nova-compute container will complain with the following error:

$ juju ssh nova-compute/0
$ sudo tail -f /var/log/nova/nova-compute.log
...
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/nova/compute/manager.py", line 2078, in _build_resources
    yield resources
  File "/usr/lib/python2.7/dist-packages/nova/compute/manager.py", line 1920, in _build_and_run_instance
    block_device_info=block_device_info)
  File "/usr/lib/python2.7/dist-packages/nova/virt/lxd/driver.py", line 317, in spawn
    self._add_ephemeral(block_device_info, lxd_config, instance)
  File "/usr/lib/python2.7/dist-packages/nova/virt/lxd/driver.py", line 1069, in _add_ephemeral
    raise exception.NovaException(reason)
NovaException: Unsupport LXD storage detected. Supported storage drivers are zfs and btrfs.

If Cinder is available, create a test Cinder volume:

$ cinder create --name testvolume 10
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