Class: Datadog::Statsd::Sender

Inherits:
Object
  • Object
show all
Defined in:
lib/datadog/statsd/sender.rb

Overview

Sender is using a companion thread to flush and pack messages in a ‘MessageBuffer`. The communication with this thread is done using a `Queue`. If the thread is dead, it is starting a new one to avoid having a blocked Sender with no companion thread to communicate with (most of the time, having a dead companion thread means that a fork just happened and that we are running in the child process).

Constant Summary collapse

CLOSEABLE_QUEUES = 
Queue.instance_methods.include?(:close)

Instance Method Summary collapse

Constructor Details

#initialize(message_buffer, telemetry: nil, queue_size: UDP_DEFAULT_BUFFER_SIZE, logger: nil, flush_interval: nil, queue_class: Queue, thread_class: Thread) ⇒ Sender

Returns a new instance of Sender.



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# File 'lib/datadog/statsd/sender.rb', line 15

def initialize(message_buffer, telemetry: nil, queue_size: UDP_DEFAULT_BUFFER_SIZE, logger: nil, flush_interval: nil, queue_class: Queue, thread_class: Thread)
  @message_buffer = message_buffer
  @telemetry = telemetry
  @queue_size = queue_size
  @logger = logger
  @mx = Mutex.new
  @queue_class = queue_class
  @thread_class = thread_class
  @done = false
  @flush_timer = if flush_interval
    Datadog::Statsd::Timer.new(flush_interval) { flush(sync: true) }
  else
    nil
  end
end

Instance Method Details

#add(message) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/datadog/statsd/sender.rb', line 64

def add(message)
  raise ArgumentError, 'Start sender first' unless message_queue

  # if the thread does not exist, we assume we are running in a forked process,
  # empty the message queue and message buffers (these messages belong to
  # the parent process) and spawn a new companion thread.
  if sender_thread.nil? || !sender_thread.alive?
    @mx.synchronize {
      # an attempt was previously made to start the sender thread but failed.
      # skipping re-start
      return if @done
      # a call from another thread has already re-created
      # the companion thread before this one acquired the lock
      break if sender_thread.alive?
      @logger.debug { "Statsd: companion thread is dead, re-creating one" } if @logger

      message_queue.close if CLOSEABLE_QUEUES
      @message_queue = nil
      message_buffer.reset
      start
      @flush_timer.start if @flush_timer && @flush_timer.stop?
    }
  end

  if message_queue.length <= @queue_size
    message_queue << message
  else
    if @telemetry
      bytesize = message.respond_to?(:bytesize) ? message.bytesize : 0
      @telemetry.dropped_queue(packets: 1, bytes: bytesize)
    end
  end
end

#flush(sync: false) ⇒ Object 



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# File 'lib/datadog/statsd/sender.rb', line 31

def flush(sync: false)
  # keep a copy around in case another thread is calling #stop while this method is running
  current_message_queue = message_queue

  # don't try to flush if there is no message_queue instantiated or
  # no companion thread running
  if !current_message_queue
    @logger.debug { "Statsd: can't flush: no message queue ready" } if @logger
    return
  end
  if !sender_thread.alive?
    @logger.debug { "Statsd: can't flush: no sender_thread alive" } if @logger
    return
  end

  current_message_queue.push(:flush)
  rendez_vous if sync
end

#rendez_vous ⇒ Object 



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# File 'lib/datadog/statsd/sender.rb', line 50

def rendez_vous
  # could happen if #start hasn't be called
  return unless message_queue

  # Initialize and get the thread's sync queue
  queue = (@thread_class.current[:statsd_sync_queue] ||= @queue_class.new)
  # tell sender-thread to notify us in the current
  # thread's queue
  message_queue.push(queue)
  # wait for the sender thread to send a message
  # once the flush is done
  queue.pop
end

#start ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/datadog/statsd/sender.rb', line 98

def start
  raise ArgumentError, 'Sender already started' if message_queue

  # initialize a new message queue for the background thread
  @message_queue = @queue_class.new
  begin
    # start background thread
    @sender_thread = @thread_class.new(&method(:send_loop))
    @sender_thread.name = "Statsd Sender" unless Gem::Version.new(RUBY_VERSION) < Gem::Version.new('2.3')
  rescue ThreadError => e
    @logger.debug { "Statsd: Failed to start sender thread: #{e.message}" } if @logger
    @mx.synchronize { @done = true }
  end

  @flush_timer.start if @flush_timer
end

#stop(join_worker: true) ⇒ Object

when calling stop, make sure that no other threads is trying to close the sender nor trying to continue to ‘#add` more message into the sender.



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# File 'lib/datadog/statsd/sender.rb', line 119

def stop(join_worker: true)
  @flush_timer.stop if @flush_timer

  message_queue = @message_queue
  message_queue.close if message_queue

  sender_thread = @sender_thread
  sender_thread.join if sender_thread && join_worker
end