config.ru

require 'faye'
require 'logger'

Faye::WebSocket.load_adapter('thin')
faye = Faye::RackAdapter.new(:mount => '/faye', :timeout => 25)

#Define hash to store metrics each time a monitoring event occurs in the server
event_metrics = {
  :connections            => {count: 0, latest_timestamp: nil},
  :active_subscriptions   => {count: 0, latest_timestamp: nil},
  :inactive_subscriptions => {count: 0, latest_timestamp: nil},
  :published_messages     => {count: 0, latest_timestamp: nil},
  :disconnections         => {count: 0, latest_timestamp: nil}
}

c_metrics = {
  :connections            => 0,
  :active_subscriptions   => 0,
  :inactive_subscriptions => 0,
  :published_messages     => 0,
  :disconnections         => 0
}

#Define hash to store metrics each time a monitoring event occurs on a channel in the server
channel_metrics = Hash.new { |k,v| k[v] = c_metrics.dup }

faye.bind(:handshake) do |client_id|
  event_timestamp = Time.now
  event_metrics[:connections][:count] += 1
  event_metrics[:connections][:latest_timestamp] = event_timestamp
  latest_metrics = {:event_metrics => event_metrics, :channel_metrics => channel_metrics}
  faye.get_client.publish('/metrics',latest_metrics)
end

faye.bind(:subscribe) do |client_id, channel|
  event_timestamp = Time.now
  event_metrics[:active_subscriptions][:count] += 1
  event_metrics[:active_subscriptions][:latest_timestamp] = event_timestamp

  unless channel.eql?('/metrics')
    channel_metrics[channel][:active_subscriptions] += 1
    channel_metrics[channel][:latest_timestamp] = event_timestamp
  end  
  latest_metrics = {:event_metrics => event_metrics, :channel_metrics => channel_metrics}
  faye.get_client.publish('/metrics',latest_metrics)
end

faye.bind(:unsubscribe) do |client_id, channel|
  event_timestamp = Time.now
  event_metrics[:inactive_subscriptions][:count] += 1
  event_metrics[:inactive_subscriptions][:latest_timestamp] = event_timestamp

  event_metrics[:active_subscriptions][:count] -= 1
  event_metrics[:active_subscriptions][:latest_timestamp] = event_timestamp

  unless channel.eql?('/metrics')
    channel_metrics[channel][:active_subscriptions] -= 1
    channel_metrics[channel][:latest_timestamp] = event_timestamp
  end  
  latest_metrics = {:event_metrics => event_metrics, :channel_metrics => channel_metrics}
  faye.get_client.publish('/metrics',latest_metrics)
end

faye.bind(:publish) do |client_id, channel, data|
  event_timestamp = Time.now
  event_metrics[:published_messages][:count] += 1
  event_metrics[:published_messages][:latest_timestamp] = event_timestamp

  unless channel.eql?('/metrics')
    channel_metrics[channel][:published_messages] += 1
    channel_metrics[channel][:latest_timestamp] = event_timestamp
    latest_metrics = {:event_metrics => event_metrics, :channel_metrics => channel_metrics}
    faye.get_client.publish('/metrics',latest_metrics)
  else
    # Do nothing; no need to publish unchanged latest_metrics to /metrics channel
  end  
end

faye.bind(:disconnect) do |client_id|
  event_timestamp = Time.now
  event_metrics[:disconnections][:count] += 1
  event_metrics[:disconnections][:latest_timestamp] = event_timestamp
  latest_metrics = {:event_metrics => event_metrics, :channel_metrics => channel_metrics}
  faye.get_client.publish('/metrics',latest_metrics)    
end

run faye