<NME> kafka.rb
<BEF> require 'logstash/namespace'
require 'logstash/outputs/base'
require 'jruby-kafka'

# Write events to a Kafka topic. This uses the Kafka Producer API to write messages to a topic on
  config_name 'kafka'
  milestone 1

  default :codec, 'plain'

  config :broker_list, :validate => :string, :default => 'localhost:9092'
  config :topic_id, :validate => :string, :default => 'test'
#     output {
#       kafka {
#         codec => plain {
#            format => "%{message}"
#         }
#       }
#     }
# For more information see http://kafka.apache.org/documentation.html#theproducer
#
# Kafka producer configuration: http://kafka.apache.org/documentation.html#producerconfigs
class LogStash::Outputs::Kafka < LogStash::Outputs::Base
  config_name 'kafka'
  milestone 1

  default :codec, 'json'
  # This is for bootstrapping and the producer will only use it for getting metadata (topics,
  # partitions and replicas). The socket connections for sending the actual data will be
  # established based on the broker information returned in the metadata. The format is
  # host1:port1,host2:port2, and the list can be a subset of brokers or a VIP pointing to a
  # subset of brokers.
  config :broker_list, :validate => :string, :default => 'localhost:9092'
  # The topic to produce the messages to
  config :topic_id, :validate => :string, :required => true
  # This parameter allows you to specify the compression codec for all data generated by this
  # producer. Valid values are "none", "gzip" and "snappy".
  config :compression_codec, :validate => %w( none gzip snappy ), :default => 'none'
  # This parameter allows you to set whether compression should be turned on for particular
  # topics. If the compression codec is anything other than NoCompressionCodec,
  # enable compression only for specified topics if any. If the list of compressed topics is
  # empty, then enable the specified compression codec for all topics. If the compression codec
  # is NoCompressionCodec, compression is disabled for all topics
  config :compressed_topics, :validate => :string, :default => ''
  # This value controls when a produce request is considered completed. Specifically,
  # how many other brokers must have committed the data to their log and acknowledged this to the
  # leader. For more info, see -- http://kafka.apache.org/documentation.html#producerconfigs
  config :request_required_acks, :validate => [-1,0,1], :default => 0
  # The serializer class for messages. The default encoder takes a byte[] and returns the same byte[]
  config :serializer_class, :validate => :string, :default => 'kafka.serializer.StringEncoder'
  # The partitioner class for partitioning messages amongst partitions in the topic. The default
  # partitioner is based on the hash of the key. If the key is null,
  # the message is sent to a random partition in the broker.
  # NOTE: topic_metadata_refresh_interval_ms controls how long the producer will distribute to a
  # partition in the topic. This defaults to 10 mins, so the producer will continue to write to a
  # single partition for 10 mins before it switches
  config :partitioner_class, :validate => :string, :default => 'kafka.producer.DefaultPartitioner'
  # The amount of time the broker will wait trying to meet the request.required.acks requirement
  # before sending back an error to the client.
  config :request_timeout_ms, :validate => :number, :default => 10000
  # This parameter specifies whether the messages are sent asynchronously in a background thread.
  # Valid values are (1) async for asynchronous send and (2) sync for synchronous send. By
  # setting the producer to async we allow batching together of requests (which is great for
  # throughput) but open the possibility of a failure of the client machine dropping unsent data.
  config :producer_type, :validate => %w( sync async ), :default => 'sync'
  # The serializer class for keys (defaults to the same as for messages if nothing is given)
  config :key_serializer_class, :validate => :string, :default => 'kafka.serializer.StringEncoder'
  # This property will cause the producer to automatically retry a failed send request. This
  # property specifies the number of retries when such failures occur. Note that setting a
  # non-zero value here can lead to duplicates in the case of network errors that cause a message
  # to be sent but the acknowledgement to be lost.
  config :message_send_max_retries, :validate => :number, :default => 3
  # Before each retry, the producer refreshes the metadata of relevant topics to see if a new
  # leader has been elected. Since leader election takes a bit of time,
  # this property specifies the amount of time that the producer waits before refreshing the
  # metadata.
  config :retry_backoff_ms, :validate => :number, :default => 100
  # The producer generally refreshes the topic metadata from brokers when there is a failure
  # (partition missing, leader not available...). It will also poll regularly (default: every
  # 10min so 600000ms). If you set this to a negative value, metadata will only get refreshed on
  # failure. If you set this to zero, the metadata will get refreshed after each message sent
  # (not recommended). Important note: the refresh happen only AFTER the message is sent,
  # so if the producer never sends a message the metadata is never refreshed
  config :topic_metadata_refresh_interval_ms, :validate => :number, :default => 600 * 1000
  # Maximum time to buffer data when using async mode. For example a setting of 100 will try to
  # batch together 100ms of messages to send at once. This will improve throughput but adds
  # message delivery latency due to the buffering.
  config :queue_buffering_max_ms, :validate => :number, :default => 5000
  # The maximum number of unsent messages that can be queued up the producer when using async
  # mode before either the producer must be blocked or data must be dropped.
  config :queue_buffering_max_messages, :validate => :number, :default => 10000
  # The amount of time to block before dropping messages when running in async mode and the
  # buffer has reached queue.buffering.max.messages. If set to 0 events will be enqueued
  # immediately or dropped if the queue is full (the producer send call will never block). If set
  # to -1 the producer will block indefinitely and never willingly drop a send.
  config :queue_enqueue_timeout_ms, :validate => :number, :default => -1
  # The number of messages to send in one batch when using async mode. The producer will wait
  # until either this number of messages are ready to send or queue.buffer.max.ms is reached.
  config :batch_num_messages, :validate => :number, :default => 200
  # Socket write buffer size
  config :send_buffer_bytes, :validate => :number, :default => 100 * 1024
  # The client id is a user-specified string sent in each request to help trace calls. It should
  # logically identify the application making the request.
  config :client_id, :validate => :string, :default => ""

  public
  def register
    LogStash::Logger.setup_log4j(@logger)
    options = {
      :broker_list => @broker_list,
      :compression_codec => @compression_codec,
      :compressed_topics => @compressed_topics,
      :request_required_acks => @request_required_acks,
      :serializer_class => @serializer_class,
      :partitioner_class => @partitioner_class,
      :request_timeout_ms => @request_timeout_ms,
      :producer_type => @producer_type,
      :key_serializer_class => @key_serializer_class,
      :message_send_max_retries => @message_send_max_retries,
      :retry_backoff_ms => @retry_backoff_ms,
      :topic_metadata_refresh_interval_ms => @topic_metadata_refresh_interval_ms,
      :queue_buffering_max_ms => @queue_buffering_max_ms,
      :queue_buffering_max_messages => @queue_buffering_max_messages,
      :queue_enqueue_timeout_ms => @queue_enqueue_timeout_ms,
      :batch_num_messages => @batch_num_messages,
      :send_buffer_bytes => @send_buffer_bytes,
      :client_id => @client_id
    }
    @producer = Kafka::Producer.new(options)
    @producer.connect

    @logger.info('Registering kafka producer', :topic_id => @topic_id, :broker_list => @broker_list)

    @codec.on_event do |event|
      begin
        @producer.send_msg(@topic_id,nil,event)
      rescue LogStash::ShutdownSignal
        @logger.info('Kafka producer got shutdown signal')
      rescue => e
        @logger.warn('kafka producer threw exception, restarting',
                     :exception => e)
      end
    end
  end # def register

  def receive(event)
    return unless output?(event)
    if event == LogStash::SHUTDOWN
      finished
      return
    end
    @codec.encode(event)
  end
    
  def teardown
    @producer.close
  end

end #class LogStash::Outputs::Kafka

<MSG> Set the default codec to JSON

Sending structured messages is oh so nice! The JSON codec
sends a JSON representation of the Logstash event on output
and parses it on input. This allows you to more easily
send data between Logstash agents using Kafka as well as
easier integration with tools sending and receiving events
from Logstash over Kafka!

<DFF> @@ -6,7 +6,7 @@ class LogStash::Outputs::Kafka < LogStash::Outputs::Base
   config_name 'kafka'
   milestone 1
 
-  default :codec, 'plain'
+  default :codec, 'json'
 
   config :broker_list, :validate => :string, :default => 'localhost:9092'
   config :topic_id, :validate => :string, :default => 'test'

Set the default codec to JSON