sensu plugin to get stats from docker containers

docker_processes.rb

#!/usr/bin/env ruby

require 'rubygems' if RUBY_VERSION < '1.9.0'
require 'sensu-plugin/metric/cli'
require 'socket'
require 'pathname'
require 'sys/proctable'

class DockerContainerMetrics < Sensu::Plugin::Metric::CLI::Graphite

  option :scheme,
         :description => 'Metric naming scheme, text to prepend to metric',
         :short => '-s SCHEME',
         :long => '--scheme SCHEME',
         :default => "docker.#{Socket.gethostname}"

  option :cgroup_path,
         :description => 'path to cgroup mountpoint',
         :short => '-c PATH',
         :long => '--cgroup PATH',
         :default => '/sys/fs/cgroup'

  option :docker_host,
         description: 'docker host',
         short: '-H DOCKER_HOST',
         long: '--docker-host DOCKER_HOST',
         default: 'tcp://127.0.1.1:4243'

  def run
    container_metrics
    ok
  end

  def container_metrics
    cgroup = Pathname(config[:cgroup_path]).join('cpu/docker')

    ps = Sys::ProcTable.ps.group_by(&:pid)
    timestamp = Time.now.to_i

    fields = [:rss, :vsize, :nswap, :pctcpu, :pctmem]

    ENV['DOCKER_HOST'] = config[:docker_host]
    containers = `docker ps --quiet --no-trunc`.split("\n")

    containers.each do |container|
      pids = cgroup.join(container).join('cgroup.procs').read.split("\n").map(&:to_i)

      processes = ps.values_at(*pids).flatten.group_by(&:comm)
      processes.each do |comm, processes|
        prefix = "#{config[:scheme]}.#{container}.#{comm}"
        fields.each do |field|
          output "#{prefix}.#{field}", processes.map(&field).reduce(:+), timestamp
        end
        # this check requires a lot of permissions, even root maybe?
        output "#{prefix}.fd", processes.map { |p| p.fd.keys.count }.reduce(:+), timestamp
      end
    end
  end
end