garethr-docker

by garethr

Puppet module for managing docker

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Puppet module for installing, configuring and managing Docker from the official repository or alternatively from EPEL on RedHat based distributions.

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This module is currently tested on:

  • Debian 8.0
  • Debian 7.8
  • Ubuntu 12.04
  • Ubuntu 14.04
  • Centos 7.0
  • Centos 6.6

It may work on other distros and additional operating systems will be supported in the future. It's definitely been used with the following too:

  • Archlinux
  • Amazon Linux
  • Fedora
  • Gentoo

Examples

Usage

The module includes a single class:

include 'docker'

By default this sets up the docker hosted repository if necessary for your OS and installs the docker package and on Ubuntu, any required Kernel extensions.

If you don't want this module to mess about with your Kernel then you can disable this feature like so. It is only enabled (and supported) by default on Ubuntu:

class { 'docker':
  manage_kernel => false,
}

If you want to configure your package sources independently, inform this module to not auto-include upstream sources (This is already disabled on Archlinux as there is no further upstream):

class { 'docker':
  use_upstream_package_source => false,
}

Docker recently launched new official repositories which are now the default for the module from version 5. If you want to stick with the old repositories you can do so with the following:

class { 'docker':
  package_name => 'lxc-docker',
  package_source_location => 'https://get.docker.com/ubuntu',
  package_key_source => 'https://get.docker.com/gpg',
  package_key => '36A1D7869245C8950F966E92D8576A8BA88D21E',
  package_release => 'docker',
}

Docker also provide a commercially supported version of the Docker Engine, called Docker CS, available from a separate repository. This can be installed with the module using the following:

class { 'docker':
  docker_cs => true,
}

The module also now uses the upstream repositories by default for RHEL based distros, including Fedora. If you want to stick with the distro packages you should use the following:

class { 'docker':
  use_upstream_package_source => false,
  package_name => 'docker',
}

By default the docker daemon will bind to a unix socket at /var/run/docker.sock. This can be changed, as well as binding to a tcp socket if required.

class { 'docker':
  tcp_bind        => ['tcp://127.0.0.1:4243','tcp://10.0.0.1:4243'],
  socket_bind     => 'unix:///var/run/docker.sock',
  ip_forward      => true,
  iptables        => true,
  ip_masq         => true,
  bridge          => br0,
  fixed_cidr      => '10.20.1.0/24',
  default_gateway => '10.20.0.1',
}

For TLS setup you should upload related files (such as CA certificate, server certificate and key) and use their paths in manifest

class { 'docker':
  tcp_bind        => ['tcp://0.0.0.0:2376'],
  tls_enable      => true,
  tls_cacert      => '/etc/docker/tls/ca.pem',
  tls_cert        => '/etc/docker/tls/cert.pem',
  tls_key         => '/etc/docker/tls/key.pem',
}

Unless specified this installs the latest version of docker from the docker repository on first run. However if you want to specify a specific version you can do so, unless you are using Archlinux which only supports the latest release. Note that this relies on a package with that version existing in the reposiroty.

class { 'docker':
  version => '0.5.5',
}

And if you want to install a specific rpm package of docker you can do so:

class { 'docker' :
  manage_package              => true,
  use_upstream_package_source => false,
  package_name                => 'docker-engine'
  package_source              => 'https://get.docker.com/rpm/1.7.0/centos-6/RPMS/x86_64/docker-engine-1.7.0-1.el6.x86_64.rpm',
  prerequired_packages        => [ 'glibc.i686', 'glibc.x86_64', 'sqlite.i686', 'sqlite.x86_64', 'device-mapper', 'device-mapper-libs', 'device-mapper-event-libs', 'device-mapper-event' ]
}

And if you want to track the latest version you can do so:

class { 'docker':
  version => 'latest',
}

In some cases dns resolution won't work well in the container unless you give a dns server to the docker daemon like this:

class { 'docker':
  dns => '8.8.8.8',
}

To add users to the Docker group you can pass an array like this:

class { 'docker':
  docker_users => ['user1', 'user2'],
}

To add daemon labels you can pass an array like this:

class { 'docker':
  labels => ['storage=ssd','stage=production'],
}

The class contains lots of other options, please see the inline code documentation for the full options.

Images

The next step is probably to install a docker image; for this we have a defined type which can be used like so:

docker::image { 'base': }

This is equivalent to running

docker pull base
. This is downloading a large binary so on first run can take a while. For that reason this define turns off the default 5 minute timeout for exec. Takes an optional parameter for installing image tags that is the equivalent to running
docker pull -t="precise" ubuntu
:
docker::image { 'ubuntu':
  image_tag => 'precise'
}

Note: images will only install if an image of that name does not already exist.

A images can also be added/build from a dockerfile with the

docker_file
property, this equivalent to running
docker build -t ubuntu - < /tmp/Dockerfile
docker::image { 'ubuntu':
  docker_file => '/tmp/Dockerfile'
}

Images can also be added/build from a directory containing a dockerfile with the

docker_dir
property, this is equivalent to running
docker build -t ubuntu /tmp/ubuntu_image
docker::image { 'ubuntu':
  docker_dir => '/tmp/ubuntu_image'
}

You can trigger a rebuild of the image by subscribing to external events like Dockerfile changes:

docker::image { 'ubuntu':
  docker_file => '/tmp/Dockerfile'
  subscribe => File['/tmp/Dockerfile'],
}

file { '/tmp/Dockerfile': ensure => file, source => 'puppet:///modules/someModule/Dockerfile', }

You can also remove images you no longer need with:

docker::image { 'base':
  ensure => 'absent'
}

docker::image { 'ubuntu': ensure => 'absent', image_tag => 'precise' }

If using hiera, there's a

docker::images
class you can configure, for example:
---
  classes:
    - docker::images

docker::images::images: ubuntu: image_tag: 'precise'

Containers

Now you have an image you can launch containers:

docker::run { 'helloworld':
  image   => 'base',
  command => '/bin/sh -c "while true; do echo hello world; sleep 1; done"',
}

This is equivalent to running the following:

docker run -d base /bin/sh -c "while true; do echo hello world; sleep 1; done"

This will launch a Docker container managed by the local init system.

Run also takes a number of optional parameters:

docker::run { 'helloworld':
  image           => 'base',
  command         => '/bin/sh -c "while true; do echo hello world; sleep 1; done"',
  ports           => ['4444', '4555'],
  expose          => ['4666', '4777'],
  links           => ['mysql:db'],
  net             => 'my-user-def-net',
  volumes         => ['/var/lib/couchdb', '/var/log'],
  volumes_from    => '6446ea52fbc9',
  memory_limit    => '10m', # (format: '', where unit = b, k, m or g)
  cpuset          => ['0', '3'],
  username        => 'example',
  hostname        => 'example.com',
  env             => ['FOO=BAR', 'FOO2=BAR2'],
  env_file        => ['/etc/foo', '/etc/bar'],
  dns             => ['8.8.8.8', '8.8.4.4'],
  restart_service => true,
  privileged      => false,
  pull_on_start   => false,
  before_stop     => 'echo "So Long, and Thanks for All the Fish"',
  before_start    => 'echo "Run this on the host before starting the Docker container"',
  after           => [ 'container_b', 'mysql' ],
  depends         => [ 'container_a', 'postgres' ],
  extra_parameters => [ '--restart=always' ],
}

Ports, expose, env, env_file, dns and volumes can be set with either a single string or as above with an array of values.

Specifying

pull_on_start
will pull the image before each time it is started.

Specifying

before_stop
will execute a command before stopping the container.

The

after
option allows expressing containers that must be started before. This affects the generation of the init.d/systemd script.

The

depends
option allows expressing container dependencies. The depended container will be started before this container(s), and this container will be stopped before the depended container(s). This affects the generation of the init.d/systemd script. You can use
depend_services
to specify dependency for generic services (non-docker) that should be started before this container.

extra_parameters
: An array of additional command line arguments to pass to the
docker run
command. Useful for adding additional new or experimental options that the module does not yet support.

The service file created for systemd based systems enables automatic restarting of the service on failure by default.

To use an image tag just append the tag name to the image name separated by a semicolon:

docker::run { 'helloworld':
  image   => 'ubuntu:precise',
  command => '/bin/sh -c "while true; do echo hello world; sleep 1; done"',
}

By default the generated init scripts will remove the container (but not any associated volumes) when the service is stopped or started. This behaviour can be modified using the following, with defaults shown:

docker::run { 'helloworld':
  remove_container_on_start => true,
  remove_volume_on_start    => false,
  remove_container_on_stop  => true,
  remove_volume_on_stop     => false,
}

If using hiera, there's a

docker::run_instance
class you can configure, for example:
---
  classes:
    - docker::run_instance

docker::run_instance::instance: helloworld: image: 'ubuntu:precise' command: '/bin/sh -c "while true; do echo hello world; sleep 1; done"'

Networks

As of Docker 1.9.x, Docker has official support for networks. The module now exposes a type,

docker_network
, used to manage those. This works like:
docker_network { 'my-net':
  ensure   => present,
  driver   => 'overlay',
  subnet   => '192.168.1.0/24',
  gateway  => '192.168.1.1',
  ip_range => '192.168.1.4/32',
}

Only the name is required, along with an ensure value. If you don't pass a driver Docker network will use the default bridge. Note that some networks require the Docker daemon to be configured to use them, for instance for the overlay network you'll need a cluster store configured. You can do that on the

docker
class like so:
extra_parameters => '--cluster-store=://172.17.8.101: --cluster-advertise=:2376'

If using hiera, there's a

docker::networks
class you can configure, for example:
---
  classes:
    - docker::networks

docker::networks::networks: local-docker: ensure: 'present' subnet: '192.168.1.0/24' gateway: '192.168.1.1'

The network defined can then be used on a

docker::run
resource with the
net
parameter.

Compose

Docker Compose allows for describing a set of containers in a simple YAML format, and then running a command to build and run those containers. The

docker_compose
type included in the module allows for using Puppet to run Compose. This means you can have Puppet remediate any issues and make sure reality matches the model in your Compose file.

Before using the docker_compose type make sure the docker-compose utility is installed:

class {'docker::compose': 
  ensure => present,
}

Here's an example. Given the following Compose file:

compose_test:
  image: ubuntu:14.04
  command: /bin/sh -c "while true; do echo hello world; sleep 1; done"

That could be added to the machine you're running Puppet using a

file
resource or any other means.

Then define a

docker_compose
resource pointing at the Compose file like so:
docker_compose { '/tmp/docker-compose.yml':
  ensure  => present,
}

Now when Puppet runs it will automatically run Compose is required, for example because the relevant Compose services aren't running.

You can also pass additional options (for example to enable experimental features) as well as provide scaling rules. The following example requests 2 containers be running for example. Puppet will now run Compose if the number of containers for a given service don't match the provided scale values.

docker_compose { '/tmp/docker-compose.yml':
  ensure  => present,
  scale   => {
    'compose_test' => 2,
  },
  options => '--x-networking'
}

It is also possible to give options to the

docker-compose up
command such as
--remove-orphans
using the
up_args
option.

Swarm mode

Docker Engine 1.12 includes swarm mode for natively managing a cluster of Docker Engines called a swarm. You can now cluster your Docker engines with the one of the following Puppet resources. For a swarm manager:

docker::swarm {'cluster_manager':
  init           => true,
  advertise_addr => '192.168.1.1',
  listen_addr    => '192.168.1.1',  
} 

In the above example we have configured a swarm manager with

init => true
then set the
advertise_addr
and
listen_addr
. Both the
advertise_addr
and
listen_addr
are set for the cluster communications between nodes. Please note the
advertise_addr
and
listen_addr
must be set for a multihomed server. For more advance flags to configure raft snapshots etc please read the readme at the top of the
docker::swarm
class.

For a swarm worker:

puppet
docker::swarm {'cluster_worker':
join           => true,
advertise_addr => '192.168.1.2',
listen_addr    => '192.168.1.2,
manager_ip     => '192.168.1.1',
token          => 'SWMTKN-1-2lw8bnr57qsu74d6iq2q1wr2wq2i334g7425dfr3zucimvh4bl-2vwn6gysbdj605l37c61iixie'
} 

In this example we have joined a node to the cluster using

join => true
. For a worker node or second manager you need to pass a current managers ip address
manager_ip => '192.168.1.1'
The other important configuration is the token you pass to the manager. The token will define the nodes role in the cluster, as there will be a token to create another manager and a different token for the worker nodes.

To remove a node from a cluster use the following:

puppet
docker::swarm {'cluster_worker':
ensure => absent
}

Docker services

Docker services allow to create distributed applications across multiple swarm nodes. A service is a set of containers that are replicated across your swarm. To configure a service with Puppet code please see the following examples

To create a service

puppet
docker::services {'redis':
    create => true,   
    service_name => 'redis',
    image => 'redis:latest',
    publish => '6379:639',
    replicas => '5', 
    extra_params => ['--update-delay 1m', '--restart-window 30s']
  }
In this example we are creating a service called
redis
, as it is a new service we have set
create => true
. The
service_name
resource is the name which Docker knows the service as. The
image
resource is the image you want to base the service off,
publish
is the ports that want exposed to the outside world for the service to be consumed,
replicas
sets the amount of tasks (containers) that you want running in the service,
extra_params
allows you to configure any of the other flags that Docker gives you when you create a service for more info see
docker service create --help

To update the service ```puppet docker::services {'redisupdate': create => false, update => true, servicename => 'redis', replicas => '3', }

In this example we have taken the service that we created earlier

redis
set the
create => false
and this time added
update => true
. We then decleared the service name
redis
we have then updated the servce to have only 3 replicas, not 5. The
extra_params
resource is also available in the update class.

To scale a service

puppet
docker::services {'redis_scale':
  create => false,
  scale => true,
  service_name => 'redis',
  replicas => '10', 
}
In this example we have used the command
docker service scale
with Puppet code. We have taken our service
redis
set the
create => false
and
scale => true
When using scale you have to declare your
service_name
then the number of replicas that you want. In this example we are going to scale to
10

To remove a service

puppet
docker::services {'redis':
  ensure => 'absent',
  service_name => 'redis',
}
To remove a a service from your swarm just set
ensure => absent
and the service_name of your service.

Private registries

By default images will be pushed and pulled from index.docker.io unless you've specified a server. If you have your own private registry without authentication, you can fully qualify your image name. If your private registry requires authentication you may configure a registry:

docker::registry { 'example.docker.io:5000':
  username => 'user',
  password => 'secret',
  email    => '[email protected]',
}

You can logout of a registry if it is no longer required.

docker::registry { 'example.docker.io:5000':
  ensure => 'absent',
}

If using hiera, there's a docker::registry_auth class you can configure, for example:

docker::registry_auth::registries:
  'example.docker.io:5000':
    username: 'user1'
    password: 'secret'
    email: '[email protected]'

Exec

Docker also supports running arbitrary commands within the context of a running container. And now so does the Puppet module.

docker::exec { 'cron_allow_root':
  detach       => true,
  container    => 'mycontainer',
  command      => '/bin/echo root >> /usr/lib/cron/cron.allow',
  tty          => true,
  unless       => 'grep root /usr/lib/cron/cron.allow 2>/dev/null',
}

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