Class: EventHub::Processor

Inherits:
Object
  • Object
show all
Includes:
Helper
Defined in:
lib/eventhub/processor.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from Helper

#class_to_array, #duration, #format_string, #get_host, #get_ip_adresses, #now_stamp

Constructor Details

#initialize(name = nil) ⇒ Processor

Returns a new instance of Processor.



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# File 'lib/eventhub/processor.rb', line 12

def initialize(name=nil)
  @name = name || class_to_array(self.class)[1..-1].join(".")
  @folder = Dir.pwd

  # Variables used for heartbeat statistics
  @started = Time.now
  @messages_successful           = 0
  @messages_unsuccessful         = 0
  @messages_average_size         = 0
  @messages_average_process_time = 0
  @first_message                 = true

  @channel_receiver = nil
  @channel_sender    = nil
  @restart = true
end

Instance Attribute Details

#folder ⇒ Object

Returns the value of attribute folder.



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# File 'lib/eventhub/processor.rb', line 4

def folder
  @folder
end

#name ⇒ Object

Returns the value of attribute name.



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# File 'lib/eventhub/processor.rb', line 4

def name
  @name
end

Instance Method Details

#configuration ⇒ Object 



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# File 'lib/eventhub/processor.rb', line 29

def configuration
  EventHub::Configuration.instance.data
end

#connection_settings ⇒ Object 



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# File 'lib/eventhub/processor.rb', line 53

def connection_settings
  { user: server_user, password: server_password, host: server_host, vhost: server_vhost }
end

#handle_message(metadata, payload) ⇒ Object 



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# File 'lib/eventhub/processor.rb', line 179

def handle_message(metadata,payload)
  raise "Please implement method in derived class"
end

#heartbeat ⇒ Object 



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# File 'lib/eventhub/processor.rb', line 207

def heartbeat
  message = Message.new
  message.origin_module_id   = @name
  message.origin_type      = "processor"
  message.origin_site_id     = 'global'

  message.process_name     = 'event_hub.heartbeat'

  now = Time.now
  message.body = {
     version:               self.version,
     heartbeat: {             
     started:               now_stamp(@started),
     stamp_last_beat:       now_stamp(now), 
     uptime:                duration(now-@started),
     heartbeat_cycle_in_s:  self.heartbeat_cycle_in_s,
     served_queues:         [self.listener_queue],
     host:                  get_host,
     ip_adresses:           get_ip_adresses,
     messages: {
      total:                @messages_successful+@messages_unsuccessful,
      successful:           @messages_successful,
      unsuccessful:         @messages_unsuccessful,
      average_size:         @messages_average_size,
      average_process_time: @messages_average_process_time 
      }
    }
  }

  # send heartbeat message
  send_message(message)

  EventMachine.add_timer(self.heartbeat_cycle_in_s) { heartbeat }

end

#heartbeat_cycle_in_s ⇒ Object 



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# File 'lib/eventhub/processor.rb', line 69

def heartbeat_cycle_in_s
  configuration.get('processor.heartbeat_cycle_in_s') || 300
end

#listener_queue ⇒ Object 



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# File 'lib/eventhub/processor.rb', line 57

def listener_queue
  configuration.get('processor.listener_queue') || 'undefined_listener_queue'
end

#restart_in_s ⇒ Object 



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# File 'lib/eventhub/processor.rb', line 65

def restart_in_s
  configuration.get('processor.restart_in_s') || 15
end

#send_message(message, exchange_name = EH_X_INBOUND) ⇒ Object

send message



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# File 'lib/eventhub/processor.rb', line 244

def send_message(message,exchange_name=EH_X_INBOUND)

  if @channel_sender.nil? || !@channel_sender.open?
    @channel_sender = AMQP::Channel.new(@connection, prefetch: 1)

    # use publisher confirm
    @channel_sender.confirm_select
      
    # @channel.on_error { |ch, channel_close| EventHub.logger.error "Oops! a channel-level exception: #{channel_close.reply_text}" }
      # @channel.on_ack   { |basic_ack| EventHub.logger.info "Received basic_ack: multiple = #{basic_ack.multiple}, delivery_tag = #{basic_ack.delivery_tag}" }
  end

  exchange = @channel_sender.direct(exchange_name, :durable => true, :auto_delete => false) 
    exchange.publish(message.to_json, :persistent => true)
end

#server_host ⇒ Object 



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# File 'lib/eventhub/processor.rb', line 33

def server_host
  configuration.get('server.host') || 'localhost'
end

#server_management_port ⇒ Object 



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# File 'lib/eventhub/processor.rb', line 45

def server_management_port
  configuration.get('server.management_port') || 15672
end

#server_password ⇒ Object 



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# File 'lib/eventhub/processor.rb', line 41

def server_password
  configuration.get('server.password') || 'admin'
end

#server_user ⇒ Object 



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# File 'lib/eventhub/processor.rb', line 37

def server_user
  configuration.get('server.user') || 'admin'
end

#server_vhost ⇒ Object 



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# File 'lib/eventhub/processor.rb', line 49

def server_vhost
  configuration.get('server.vhost') || 'event_hub'
end

#sleep_break(seconds) ⇒ Object

breaks after n seconds or after interrupt



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# File 'lib/eventhub/processor.rb', line 260

def sleep_break( seconds ) # breaks after n seconds or after interrupt
    while (seconds > 0)
      sleep(1)
      seconds -= 1
      break unless @restart
    end
end

#start(detached = false) ⇒ Object 



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# File 'lib/eventhub/processor.rb', line 73

def start(detached=false)
  daemonize if detached

  EventHub.logger.info("Processor [#{@name}] base folder [#{@folder}]")

  while @restart

    begin 
      AMQP.start(self.connection_settings) do |connection, open_ok|

        @connection = connection
        
        # deal with tcp connection issues
        @connection.on_tcp_connection_loss do |conn, settings|
          EventHub.logger.warn("Processor lost tcp connection. Trying to restart in #{self.restart_in_s} seconds...")
          stop_processor(true)
        end

        # create channel
        @channel_receiver = AMQP::Channel.new(@connection, prefetch: 1)

        # connect to queue
        @queue = @channel_receiver.queue(self.listener_queue, durable: true, auto_delete: false)

        # subscribe to queue
        @queue.subscribe(:ack => true) do |metadata, payload|     
         begin
           start_stamp = Time.now
           messages_to_send = []

           # try to convert to Evenhub message
           message = Message.from_json(payload)
           EventHub.logger.info("-> #{message.to_s}")

           if message.status_code == STATUS_INVALID
             messages_to_send << message
             EventHub.logger.info("-> #{message.to_s} => Put to queue [#{EH_X_INBOUND}].")
           else
              # pass received message to handler or dervied handler
              messages_to_send = Array(handle_message(message))
            end

           # forward invalid or returned messages to dispatcher
            messages_to_send.each do |message|
              send_message(message)
            end
            @channel_receiver.acknowledge(metadata.delivery_tag)

            # collect statistics for the heartbeat
            @messages_successful += 1
            if @first_message
              @messages_average_process_time = Time.now - start_stamp
              @messages_average_size = payload.size
              @first_message = false
            else
              @messages_average_process_time = (@messages_average_process_time + (Time.now - start_stamp))/2.0
              @messages_average_size = (@messages_average_size + payload.size) / 2.0
            end
            
         rescue => e
           @channel_receiver.reject(metadata.delivery_tag,false)
           @messages_unsuccessful += 1
           EventHub.logger.error("Unexpected exception in handle_message method: #{e}. Message dead lettered.")
            EventHub.logger.save_detailed_error(e)
         end
        end

        EventHub.logger.info("Processor [#{@name}] is listening to vhost [#{self.server_vhost}], queue [#{self.listener_queue}]")

        # Singnal Listening
        Signal.trap("TERM") {stop_processor}
        Signal.trap("INT")  {stop_processor}

        # post_start is a custom post start routing to be overwritten
        post_start

        # Various timers
        EventMachine.add_timer(@watchdog_cycle_in_s) { watchdog }

        heartbeat
      end
    rescue => e
      Signal.trap("TERM") { stop_processor }
      Signal.trap("INT")  { stop_processor }

      id = EventHub.logger.save_detailed_error(e)
      EventHub.logger.error("Unexpected exception: #{e}, see => #{id}. Trying to restart in #{self.restart_in_s} seconds...")
      
      sleep_break self.restart_in_s
    end

  end # while

  # post_start is a custom post start routing to be overwritten
  post_stop

  EventHub.logger.info("Processor [#{@name}] has been stopped")
ensure
  # remove pid file
  begin
    File.delete("#{@folder}/pids/#{@name}.pid") 
  rescue
    # ignore exceptions here
  end
end

#version ⇒ Object 



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# File 'lib/eventhub/processor.rb', line 8

def version
  "1.0.0"
end

#watchdog ⇒ Object 



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# File 'lib/eventhub/processor.rb', line 183

def watchdog
  begin
    response = RestClient.get "http://#{self.server_user}:#{self.server_password}@#{self.server_host}:#{self.server_management_port}/api/queues/#{self.server_vhost}/#{self.listener_queue}/bindings", { :content_type => :json}
      data = JSON.parse(response.body)
  
      if response.code != 200
        EventHub.logger.warn("Watchdog: Server did not answered properly. Trying to restart in #{self.restart_in_s} seconds...")
        EventMachine.add_timer(self.restart_in_s) { stop_processor(true) }
      elsif data.size == 0
        EventHub.logger.warn("Watchdog: Something is wrong with the vhost, queue, and/or bindings. Trying to restart in #{self.restart_in_s} seconds...")
        EventMachine.add_timer(self.restart_in_s) { stop_processor(true) }
        # does it make sence ? Needs maybe more checks in future
      else
        # Watchdog is happy :-)
      # add timer for next check
      EventMachine.add_timer(self.watchdog_cycle_in_s) { watchdog }
    end 
      
  rescue => e
    EventHub.logger.error("Watchdog: Unexpected exception: #{e}. Trying to restart in #{self.restart_in_s} seconds...")
    stop_processor
  end
end

#watchdog_cycle_in_s ⇒ Object 



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# File 'lib/eventhub/processor.rb', line 61

def watchdog_cycle_in_s
  configuration.get('processor.watchdog_cycle_is_s') || 15
end