Class: Phobos::Listener

Inherits:
Object
  • Object
show all
Includes:
Instrumentation
Defined in:
lib/phobos/listener.rb

Constant Summary collapse

KAFKA_CONSUMER_OPTS = 
%i(session_timeout offset_commit_interval offset_commit_threshold heartbeat_interval).freeze
DEFAULT_MAX_BYTES_PER_PARTITION =

512 KB

524288

Constants included from Instrumentation

Instrumentation::NAMESPACE

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from Instrumentation

#instrument, #measure, subscribe, unsubscribe

Constructor Details

#initialize(handler:, group_id:, topic:, min_bytes: nil, max_wait_time: nil, force_encoding: nil, start_from_beginning: true, backoff: nil, max_bytes_per_partition: DEFAULT_MAX_BYTES_PER_PARTITION) ⇒ Listener

Returns a new instance of Listener.



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# File 'lib/phobos/listener.rb', line 11

def initialize(handler:, group_id:, topic:, min_bytes: nil,
               max_wait_time: nil, force_encoding: nil,
               start_from_beginning: true, backoff: nil,
               max_bytes_per_partition: DEFAULT_MAX_BYTES_PER_PARTITION)
  @id = SecureRandom.hex[0...6]
  @handler_class = handler
  @group_id = group_id
  @topic = topic
  @backoff = backoff
  @subscribe_opts = {
    start_from_beginning: start_from_beginning,
    max_bytes_per_partition: max_bytes_per_partition
  }
  @encoding = Encoding.const_get(force_encoding.to_sym) if force_encoding
  @consumer_opts = compact(min_bytes: min_bytes, max_wait_time: max_wait_time)
  @kafka_client = Phobos.create_kafka_client
  @producer_enabled = @handler_class.ancestors.include?(Phobos::Producer)
end

Instance Attribute Details

#encoding ⇒ Object (readonly)

Returns the value of attribute encoding.



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# File 'lib/phobos/listener.rb', line 9

def encoding
  @encoding
end

#group_id ⇒ Object (readonly)

Returns the value of attribute group_id.



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# File 'lib/phobos/listener.rb', line 8

def group_id
  @group_id
end

#handler_class ⇒ Object (readonly)

Returns the value of attribute handler_class.



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# File 'lib/phobos/listener.rb', line 9

def handler_class
  @handler_class
end

#id ⇒ Object (readonly)

Returns the value of attribute id.



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# File 'lib/phobos/listener.rb', line 8

def id
  @id
end

#topic ⇒ Object (readonly)

Returns the value of attribute topic.



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# File 'lib/phobos/listener.rb', line 8

def topic
  @topic
end

Instance Method Details

#create_exponential_backoff ⇒ Object 



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# File 'lib/phobos/listener.rb', line 107

def create_exponential_backoff
  Phobos.create_exponential_backoff(@backoff)
end

#should_stop? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/phobos/listener.rb', line 111

def should_stop?
  @signal_to_stop == true
end

#start ⇒ Object 



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# File 'lib/phobos/listener.rb', line 30

def start
  @signal_to_stop = false
  instrument('listener.start', listener_metadata) do
    @consumer = create_kafka_consumer
    @consumer.subscribe(topic, @subscribe_opts)

    # This is done here because the producer client is bound to the current thread and
    # since "start" blocks a thread might be used to call it
    @handler_class.producer.configure_kafka_client(@kafka_client) if @producer_enabled

    instrument('listener.start_handler', listener_metadata) { @handler_class.start(@kafka_client) }
    Phobos.logger.info { Hash(message: 'Listener started').merge(listener_metadata) }
  end

  begin
    @consumer.each_batch(@consumer_opts) do |batch|
      batch_metadata = {
        batch_size: batch.messages.count,
        partition: batch.partition,
        offset_lag: batch.offset_lag,
        # the offset of the most recent message in the partition
        highwater_mark_offset: batch.highwater_mark_offset
      }.merge(listener_metadata)

      instrument('listener.process_batch', batch_metadata) do |batch_metadata|
        time_elapsed = measure do
          Phobos::Actions::ProcessBatch.new(
            listener: self,
            batch: batch,
            listener_metadata: listener_metadata
          ).execute
        end
        batch_metadata.merge!(time_elapsed: time_elapsed)
        Phobos.logger.info { Hash(message: 'Committed offset').merge(batch_metadata) }
      end

      return if should_stop?
    end

  # Abort is an exception to prevent the consumer from committing the offset.
  # Since "listener" had a message being retried while "stop" was called
  # it's wise to not commit the batch offset to avoid data loss. This will
  # cause some messages to be reprocessed
  #
  rescue Kafka::ProcessingError, Phobos::AbortError
    instrument('listener.retry_aborted', listener_metadata) do
      Phobos.logger.info({ message: 'Retry loop aborted, listener is shutting down' }.merge(listener_metadata))
    end
  end

ensure
  instrument('listener.stop', listener_metadata) do
    instrument('listener.stop_handler', listener_metadata) { @handler_class.stop }

    @consumer&.stop

    if @producer_enabled
      @handler_class.producer.async_producer_shutdown
      @handler_class.producer.configure_kafka_client(nil)
    end

    @kafka_client.close
    if should_stop?
      Phobos.logger.info { Hash(message: 'Listener stopped').merge(listener_metadata) }
    end
  end
end

#stop ⇒ Object 



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# File 'lib/phobos/listener.rb', line 98

def stop
  return if should_stop?
  instrument('listener.stopping', listener_metadata) do
    Phobos.logger.info { Hash(message: 'Listener stopping').merge(listener_metadata) }
    @consumer&.stop
    @signal_to_stop = true
  end
end