dev-lxc

A tool for creating Chef Server clusters with a Chef Analytics server using LXC containers.

Using ruby-lxc it builds a standalone Chef Server or tier Chef Server cluster composed of a backend and multiple frontends with round-robin DNS resolution. It will also optionally build a Chef Analytics server and connect it with the Chef Server.

The dev-lxc tool is well suited as a tool for support related work, customized cluster builds for demo purposes, as well as general experimentation and exploration.

Features

  1. LXC 1.0 Containers - Resource efficient servers with fast start/stop times and standard init
  2. Btrfs - Efficient storage backend provides fast, lightweight container cloning
  3. Dnsmasq - DHCP networking and DNS resolution
  4. Base containers - Containers that are built to resemble a traditional server
  5. ruby-lxc - Ruby bindings for liblxc
  6. YAML - Simple, customizable definition of clusters; No more setting ENV variables
  7. Build process closely follows online installation documentation

Its containers, standard init, networking and build process are designed to be similar to what you would build if you follow the online installation documentation so the end result is a cluster that is relatively similar to a more traditionally built cluster.

The Btrfs backed clones provide a quick clean slate which is helpful especially for experimenting and troubleshooting. Or it can be used to build a customized cluster for demo purposes and be able to bring it up quickly and reliably.

If you aren't familiar with using containers please read this introduction.

LXC 1.0 Introduction

Requirements

  • dev-lxc-platform

    The dev-lxc tool is designed to be used in a platform built by dev-lxc-platform.

    Please follow the dev-lxc-platform usage instructions to create a suitable platform.

    The dev-lxc-platform will automatically install this dev-lxc tool.

  • Use root user

    Once you login to the Vagrant VM platform you should run sudo -i to login as the root user.

    Consider using byobu or tmux for a terminal multiplexer as dev-lxc-platform README describes.

  • Setup Mounts and Packages

    As described below dev-lxc uses a dev-lxc.yml config file for each cluster. Be sure that you configure the mounts and packages lists in dev-lxc.yml to match your particular environment.

Update dev-lxc gem

Run gem update dev-lxc inside the Vagrant VM platform to ensure you have the latest version.

Usage

Display Help

dev-lxc help

dev-lxc -h

dev-lxc --help

dev-lxc help <subcommand>

Shorter Commands are Faster (to type that is :)

The dev-lxc-platform's root user's ~/.bashrc file has aliased dl to dev-lxc for ease of use but for most instructions in this README I will use dev-lxc for clarity.

You only have to type enough of a dev-lxc subcommand to make it unique.

The following commands are equivalent:

dev-lxc init standalone > dev-lxc.yml
dl i standalone > dev-lxc.yml

dev-lxc start
dl start

# if no subcommand is given then `start` will be called by default
# and any arguments will be passed to the `start` subcommand
# so both of the following commands will start all servers
dev-lxc
dl

dev-lxc status
dl stat

dev-lxc destroy
dl d

Create and Manage a Cluster

The following instructions will build a tier cluster with an Analytics server for demonstration purposes. The size of this cluster uses about 3GB ram and takes awhile for the first build of the servers. Feel free to try the standalone config first.

Define cluster

The following command saves a predefined config to dev-lxc.yml.

Be sure you configure the mounts and packages entries appropriately.

dev-lxc init tier > dev-lxc.yml

Uncomment the Analytics server section in dev-lxc.yml if you want it to be built.

Start cluster

Starting the cluster the first time takes awhile since it has a lot to build.

The tool automatically creates snapshot clones at appropriate times so future creation of the cluster's servers is very quick.

dev-lxc start

A test org, user, knife.rb and keys are automatically created in the bootstrap backend server in /root/chef-repo/.chef for testing purposes.

The knife-opc plugin is installed in the embedded ruby environment of the Private Chef and Enterprise Chef server to facilitate the creation of the test org and user.

Cluster status

Run the following command to see the status of the cluster.

dev-lxc status

This is an example of the output.

Cluster is available at https://chef.lxc
Analytics is available at https://analytics.lxc
         tier-be.lxc     running         10.0.3.203
        tier-fe1.lxc     running         10.0.3.204
  tier-analytics.lxc     running         10.0.3.206

https://chef.lxc resolves to the frontend.

Create chef-repo

Create a local chef-repo with appropriate knife.rb and pem files.

dev-lxc chef-repo

Now you can easily use knife to access the cluster.

cd chef-repo
knife ssl fetch
knife client list

Cheap cluster rebuilds

Clones of the servers as they existed immediately after initial installation, configuration and test org and user creation are available so you can destroy the cluster and "rebuild" it within seconds effectively starting with a clean slate very easily.

dev-lxc destroy
dev-lxc start

Stop and start the cluster

dev-lxc stop
dev-lxc start

Backdoor access to each server's filesystem

The abspath subcommand can be used to prepend each server's rootfs path to a particular file.

For example, you can use the following command to edit the backend and frontend servers' chef-server.rb file without logging into the containers.

emacs $(dev-lxc abspath 'be|fe' /etc/opscode/chef-server.rb)

Run arbitrary commands in each server

After modifying the chef-server.rb you could use the run_command subcommand to tell the backend and frontend servers to run chef-server-ctl reconfigure.

dev-lxc run_command 'be|fe' 'chef-server-ctl reconfigure'

Destroy cluster

Use the following command to destroy the cluster's servers and also destroy their unique and shared base containers if you want to build them from scratch.

dev-lxc destroy -u -s

Use commands against a specific server

You can also run most of these commands against a set of servers by specifying a pattern that matches a set of server names.

dev-lxc <subcommand> [pattern]

For example, to only start the backend and frontend servers named tier-be.lxc and tier-fe1.lxc you can run the following command.

dev-lxc start 'be|fe'

Using the dev-lxc library

dev-lxc cli interface can be used as a library.

require 'dev-lxc/cli'

ARGV = [ 'start' ]         # start all servers
DevLXC::CLI::DevLXC.start

ARGV = [ 'status' ]        # show status of all servers
DevLXC::CLI::DevLXC.start

ARGV = [ 'run_command', 'uptime' ]   # run `uptime` in all servers
DevLXC::CLI::DevLXC.start

ARGV = [ 'destroy' ]       # destroy all servers
DevLXC::CLI::DevLXC.start

dev-lxc itself can also be used as a library

require 'yaml'
require 'dev-lxc'

config = YAML.load(IO.read('dev-lxc.yml'))
server = DevLXC::ChefServer.new("tier-fe1.lxc", config)

server.start               # start tier-fe1.lxc
server.status              # show status of tier-fe1.lxc
server.run_command("chef-server-ctl reconfigure")  # run command in tier-fe1.lxc
server.stop                # stop tier-fe1.lxc

Cluster Config Files

dev-lxc uses a YAML configuration file named dev-lxc.yml to define a cluster.

The following command generates sample config files for various cluster topologies.

dev-lxc init

dev-lxc init tier > dev-lxc.yml creates a dev-lxc.yml file with the following content:

platform_container: p-ubuntu-1404
topology: tier
api_fqdn: chef.lxc
#analytics_fqdn: analytics.lxc
mounts:
  - /dev-shared dev-shared
packages:
  server: /dev-shared/chef-packages/cs/chef-server-core_12.0.5-1_amd64.deb
#  manage: /dev-shared/chef-packages/manage/opscode-manage_1.11.2-1_amd64.deb
#  reporting: /dev-shared/chef-packages/reporting/opscode-reporting_1.2.3-1_amd64.deb
#  push-jobs-server: /dev-shared/chef-packages/push-jobs-server/opscode-push-jobs-server_1.1.6-1_amd64.deb
#  analytics: /dev-shared/chef-packages/analytics/opscode-analytics_1.1.1-1_amd64.deb
servers:
  tier-be.lxc:
    role: backend
    ipaddress: 10.0.3.203
    bootstrap: true
  tier-fe1.lxc:
    role: frontend
    ipaddress: 10.0.3.204
#  tier-fe2.lxc:
#    role: frontend
#    ipaddress: 10.0.3.205
#  tier-analytics.lxc:
#    role: analytics
#    ipaddress: 10.0.3.206

This config defines a tier cluster consisting of a single backend and a single frontend.

A second frontend is commented out to conserve resources. If you uncomment the second frontend then both frontends will be created and dnsmasq will resolve the api_fqdn chef.lxc to both frontends using a round-robin policy.

The config file is very customizable. You can add or remove mounts, packages or servers, change ip addresses, change server names, change the base_platform and more.

The mounts list describes what directories get mounted from the Vagrant VM platform into each container. You need to make sure that you configure the mount entries to be appropriate for your environment.

The same is true for the packages list. The paths that are provided in the default configs are just examples. You need to make sure that you have each package you want to use downloaded to appropriate directories that will be available to the container when it is started.

I recommend downloading the packages to a directory on your workstation. Then configure the dev-lxc-platform's .kitchen.yml to mount that directory in the Vagrant VM platform. Then configure the cluster's mount entries in dev-lxc.yml to mount the Vagrant VM platform's directory into each container.

Make sure the mounts and packages represent actual paths that are available in your environment.

Managing Multiple Clusters

By default, dev-lxc looks for a dev-lxc.yml file in the present working directory. You can also specify a particular config file as an option for most dev-lxc commands.

The following is an example of managing multiple clusters while still avoiding specifying each cluster's config file.

mkdir -p ~/clusters/{clusterA,clusterB}
dev-lxc init tier > ~/clusters/clusterA/dev-lxc.yml
dev-lxc init standalone > ~/clusters/clusterB/dev-lxc.yml
cd ~/clusters/clusterA && dev-lxc start  # starts clusterA
cd ~/clusters/clusterB && dev-lxc start  # starts clusterB

Maintain Uniqueness Across Multiple Clusters

The default cluster configs are already designed to be unique from each other but as you build more clusters you have to maintain uniqueness across the YAML config files for the following items.

  • Server names and api_fqdn

    Server names should really be unique across all clusters.

    Even when cluster A is shutdown, if cluster B uses the same server names when it is created it will use the already existing servers from cluster A.

    api_fqdn uniqueness only matters when clusters with the same api_fqdn are running.

    If cluster B is started with the same api_fqdn as an already running cluster A, then cluster B will overwrite cluster A's DNS resolution of api_fqdn.

    It is easy to provide uniqueness. For example, you can use the following command to replace .lxc with -1234.lxc in a cluster's config.

    sed -i 's/\.lxc/-1234.lxc/' dev-lxc.yml

  • IP Addresses

    IP addresses uniqueness only matters when clusters with the same IP's are running.

    If cluster B is started with the same IP's as an already running cluster A, then cluster B will overwrite cluster A's DHCP reservation of the IP's but dnsmasq will still refuse to assign the IP's to cluster B because they already in use by cluster A. dnsmasq then assigns random IP's from the DHCP pool to cluster B leaving it in an unexpected state.

    The dev-lxc-platform creates the IP range 10.0.3.150 - 254 for DHCP reserved IP's.

    Use unique IP's from that range when configuring clusters.

Base Containers

One of the key things this tool uses is the concept of "base" containers.

dev-lxc creates base containers with a "p-", "s-" or "u-" prefix on the name to distinguish it as a "platform", "shared" or "unique" base container.

Base containers are then snapshot cloned using the btrfs filesystem to very quickly provide a lightweight duplicate of the base container. This clone is either used to build another base container or a container that will actually be run.

During a cluster build process the base containers that get created fall into three categories.

  1. Platform

    The platform base container is the first to get created and is identified by the "p-" prefix on the container name.

    DevLXC#create_base_platform controls the creation of a platform base container.

    This container provides the chosen OS platform and version (e.g. p-ubuntu-1404). A typical LXC container has minimal packages installed so dev-lxc makes sure that the same packages used in Chef's bento boxes are installed to provide a more typical server environment. A few additional packages are also installed.

    Once this platform base container is created there is rarely a need to delete it.

  2. Shared

    The shared base container is the second to get created and is identified by the "s-" prefix on the container name.

    DevLXC::ChefServer#create_base_server controls the creation of a shared base container.

    Chef packages that are common to all servers in a Chef cluster, such as chef-server-core, opscode-reporting and opscode-push-jobs-server are installed using dpkg or rpm.

    Note the manage package will not be installed at this point since it is not common to all servers (i.e. it does not get installed on backend servers).

    The name of this base container is built from the names and versions of the Chef packages that get installed which makes this base container easy to be reused by another cluster that is configured to use the same Chef packages.

    Since no configuration actually happens yet there is rarely a need to delete this container.

  3. Unique

    The unique base container is the last to get created and is identified by the "u-" prefix on the container name.

    DevLXC::ChefServer#create controls the creation of a unique base container.

    Each unique Chef server (e.g. standalone, backend or frontend) is created.

* The specified hostname is assigned.
* dnsmasq is configured to reserve the specified IP address for the container's MAC address.
* A DNS entry is created in dnsmasq if appropriate.
* All installed Chef packages are configured.
* Test users and orgs are created.
* The opscode-manage package is installed and configured if specified.

After each server is fully configured a snapshot clone of it is made resulting in the server's
unique base container. These unique base containers make it very easy to quickly recreate
a Chef cluster from a clean starting point.

Destroying Base Containers

When using dev-lxc destroy to destroy servers you have the option to also destroy any or all of the three types of base containers associated with the servers.

The following command will list the options available.

dev-lxc help destroy

Of course, you can also just use the standard LXC commands to destroy any container.

lxc-destroy -n [NAME]

Manually Create a Platform Base Container

Platform base containers can be used for purposes other than building clusters. For example, they can be used as Chef nodes for testing purposes.

You can see a menu of platform base containers this tool can create by using the following command.

dev-lxc create

The initial creation of platform base containers can take awhile so let's go ahead and start creating an Ubuntu 12.04 base container now.

dev-lxc create p-ubuntu-1404

Contributing

  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request