Refactor: reduce locking while appending events

lib/logstash/outputs/kafka.rb

@@ -1,6 +1,7 @@
 require 'logstash/namespace'
 require 'logstash/outputs/base'
 require 'java'
+require 'concurrent/map'
 require 'logstash-integration-kafka_jars.rb'
 require 'logstash/plugin_mixins/kafka_support'
 
@@ -190,7 +191,7 @@ class LogStash::Outputs::Kafka < LogStash::Outputs::Base
 
   public
   def register
-    @thread_batch_map = Concurrent::Hash.new
+    @thread_batch_map = Concurrent::Map.new
 
     if !@retries.nil? 
       if @retries < 0
@@ -204,34 +205,33 @@ def register
     @producer = create_producer
     if value_serializer == 'org.apache.kafka.common.serialization.StringSerializer'
       @codec.on_event do |event, data|
-        write_to_kafka(event, data)
+        push_event_data(event, data)
       end
     elsif value_serializer == 'org.apache.kafka.common.serialization.ByteArraySerializer'
       @codec.on_event do |event, data|
-        write_to_kafka(event, data.to_java_bytes)
+        push_event_data(event, data.to_java_bytes)
       end
     else
       raise ConfigurationError, "'value_serializer' only supports org.apache.kafka.common.serialization.ByteArraySerializer and org.apache.kafka.common.serialization.StringSerializer" 
     end
   end
 
-  def prepare(record)
+  def append_record(record)
     # This output is threadsafe, so we need to keep a batch per thread.
-    @thread_batch_map[Thread.current].add(record)
+    @thread_batch_map[Thread.current] << record
   end
 
   def multi_receive(events)
-    t = Thread.current
-    if !@thread_batch_map.include?(t)
-      @thread_batch_map[t] = java.util.ArrayList.new(events.size)
-    end
+    key = Thread.current
+
+    batch = @thread_batch_map.get(key)
+    batch = @thread_batch_map.fetch_or_store(key, Array.new(events.size)) unless batch
 
     events.each do |event|
       break if event == LogStash::SHUTDOWN
       @codec.encode(event)
     end
 
-    batch = @thread_batch_map[t]
     if batch.any?
       retrying_send(batch)
       batch.clear
@@ -315,13 +315,13 @@ def handle_kafka_error(e, record)
     end
   end
 
-  def write_to_kafka(event, serialized_data)
+  def push_event_data(event, serialized_data)
     if @message_key.nil?
       record = ProducerRecord.new(event.sprintf(@topic_id), serialized_data)
     else
       record = ProducerRecord.new(event.sprintf(@topic_id), event.sprintf(@message_key), serialized_data)
     end
-    prepare(record)
+    append_record(record)
   rescue LogStash::ShutdownSignal
     logger.debug('producer received shutdown signal')
   rescue => e