Module: OMQ::QoS::PullExt

Defined in:
lib/omq/qos/routing_ext.rb

Overview

Prepended onto Routing::Pull. At QoS >= 1 every received message is ACK'd back to the sender. At QoS >= 2 the ACK is paired with a dedup-set check: seen digests are ACK'd again but not redelivered to the application.

ACK after successful enqueue into recv_queue. A receiver that has read a frame off the wire but not yet stored it (because the app-facing recv_queue is at recv_hwm) has NOT yet taken responsibility for it — if we ACK'd on wire-receipt and then crashed before the app dequeued, the sender would have cleared pending on a message that was effectively lost. ACK-after-enqueue keeps the at-least-once contract honest and lets recv_hwm bound truly-in-flight (= read-but-not-stored) messages at zero.

The transform returns nil so the pump's own post-transform enqueue is skipped — we already enqueued inside the transform.

Instance Method Summary collapse

Instance Method Details

#connection_added(conn) ⇒ Object 



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# File 'lib/omq/qos/routing_ext.rb', line 362

def connection_added(conn)
  qos = @engine.options.qos
  return super if qos.nil?
  return super if QoS.reliable_transport?(conn)

  algo       = QoS.algo_for(conn)
  recv_queue = @recv_queue
  engine     = @engine

  case qos.level
  when 1
    engine.start_recv_pump(conn, recv_queue) do |msg|
      recv_queue.enqueue(msg)
      conn.send_command(QoS.ack_command(msg, algorithm: algo))
      nil
    end

  when 2
    dedup = qos.dedup_set_for(conn)
    QoS.install_qos2_receiver_handler(conn, dedup)

    engine.start_recv_pump(conn, recv_queue) do |msg|
      digest = QoS.digest(msg, algorithm: algo)
      ack    = Protocol::ZMTP::Codec::Command.ack(digest, algorithm: algo)

      if dedup.seen?(digest)
        conn.send_command(ack)
      else
        dedup.add(digest)
        recv_queue.enqueue(msg)
        conn.send_command(ack)
      end
      nil
    end

  when 3
    dedup = qos.dedup_set_for(conn)
    QoS.install_qos2_receiver_handler(conn, dedup)

    engine.start_recv_pump(conn, recv_queue) do |msg|
      digest = QoS.digest(msg, algorithm: algo)
      if dedup.seen?(digest)
        conn.send_command(Protocol::ZMTP::Codec::Command.comp(digest, algorithm: algo))
      else
        recv_queue.enqueue(QoS::Envelope.new(parts: msg, conn: conn, digest: digest, algo: algo))
      end
      nil
    end
  end
end