perf: reuse inner packforward payload unpacker

Author: yaauie

CHANGELOG.md

@@ -1,3 +1,6 @@
+## 3.4.2
+  - Fix: reduce overhead of unpacking packforward-payloads by reusing a single instance
+
 ## 3.4.1
   - Fix: handle multiple PackForward-encoded messages in a single payload [#28](https://github.com/logstash-plugins/logstash-codec-fluent/pull/28)
 

lib/logstash/codecs/fluent.rb

@@ -54,6 +54,7 @@ def register
     end
     @packer = @factory.packer
     @decoder = @factory.unpacker
+    @packforward_decoder = nil
   end
 
   def decode(data, &block)
@@ -117,7 +118,7 @@ def decode_event(data, &block)
         raise(LogStash::Error, "PackedForward with compression is not supported")
       end
 
-      entries_decoder = @factory.unpacker
+      entries_decoder = (@packforward_decoder ||= @factory.unpacker).tap(&:reset)
       entries_decoder.feed_each(entries) do |entry|
         yield generate_event(entry[1], entry[0], tag)
       end

logstash-codec-fluent.gemspec

@@ -1,7 +1,7 @@
 Gem::Specification.new do |s|
 
   s.name            = 'logstash-codec-fluent'
-  s.version         = '3.4.1'
+  s.version         = '3.4.2'
   s.licenses        = ['Apache License (2.0)']
   s.summary         = "Reads the `fluentd` `msgpack` schema"
   s.description     = "This gem is a Logstash plugin required to be installed on top of the Logstash core pipeline using $LS_HOME/bin/logstash-plugin install gemname. This gem is not a stand-alone program"