[docker-daemon] Add recipe and tests

[kurochan]

Add a recipe to create an agent configuration file in order to monitor docker with "docker_daemon" check.
Because "docker" check is deprecated.
The attributes available following:

datadog: {
  docker: {
    init_config: {
      docker_root: '/',
      socket_timeout: 10,
      tls: false,
      tls_client_cert: '/path/to/client-cert.pem',
      tls_client_key: '/path/to/client-key.pem',
      tls_cacert: '/path/to/ca.pem',
      tls_verify: true
    },
    instances: [
      {
        url: 'unix://var/run/docker.sock',
        tags: [
          'toto',
          'tata'
        ],
        include: [
          'docker_image:ubuntu',
          'docker_image:debian'
        ],
        exclude: [
          '.*'
        ],
        performance_tags: [
          'container_name',
          'image_name',
          'image_tag',
          'docker_image'
        ],
        container_tags: [
          'image_name',
          'image_tag',
          'docker_image'
        ],
        collect_labels_as_tags: [
          'com.docker.compose.service',
          'com.docker.compose.project'
        ],
        ecs_tags: true,
        collect_events: true,
        collect_container_size: false,
        collect_image_size: false,
        collect_images_stats: false
      }
    ]
  }
}

[miketheman]

@kurochan Thanks! Could you possibly try to replace this section with a similar one to the instances one? This retains flexibility in the Chef template if/when the Agent config changes.

Something like:

<%= JSON.parse(({ 'init_config' => @ init_config }).to_json).to_yaml %>

[miketheman]

Nice stuff, thanks!

I added a note in the template that should be addressed.

Also, you may want to add a spec test for faster feedback - this is something I have started to do with recent changes. See https://github.com/DataDog/chef-datadog/blob/master/spec/integrations/redis_spec.rb for an example.

Running rspec spec/integrations/redis_spec.rb is much faster than running a complete kitchen test.

[kurochan]

@miketheman Thank you for reviewing.
I fixed spec and template. Is this OK?

[miketheman]

@kurochan This looks good, thank you!