Fallback to plain text does not work when the message can not be unpacked

Start with lib/logstash/codecs/msgpack.rb around the rescue path at line 36 and compare it with the UDP input backtrace in the report. Reproduce the malformed msgpack input shown in the logs and verify that fallback produces a plain-text event tagged with _msgpackparsefailure while Logstash continues reading subsequent messages.

Technical context

OS : linux (in the docker container for logstash)
Gem Version : 3.0.2

Config file

input {
  udp {
    port => 1518 
    type => udp
    codec => "msgpack"
  }
}


filter {
    geoip {
        source => "ip"
    }
}


output {
  elasticsearch {
  	hosts => ["es1", "es2"]
        index => "logstash-activities-%{+YYYY.MM.dd}"
        document_id => "%{id}"

	}
  stdout {
		codec => "json"
	}
}

The problem

sometimes, my client send wrong messages to my logstash server probably due to UDP.
The message can not be unpacked correctly by msgpack and the failover to plain text does not work and crash logstash reader.
Logstash stop reading messages from this point but does not crash completely.

Logs

WARN  logstash.codecs.msgpack - Trouble parsing msgpack input, falling back to plain text {:input=>"\x00", :exception=>#}
09:10:47.013 ["\x00", :exception=>#}
09:10:47.013 [#, "backtrace"=>["/usr/share/logstash/vendor/bundle/jruby/1.9/gems/logstash-codec-msgpack-3.0.2-java/lib/logstash/codecs/msgpack.rb:36:in `decode'", "/usr/share/logstash/vendor/bundle/jruby/1.9/gems/logstash-codec-msgpack-3.0.2-java/lib/logstash/codecs/msgpack.rb:29:in `decode'", "/usr/share/logstash/vendor/bundle/jruby/1.9/gems/logstash-input-udp-3.1.0/lib/logstash/inputs/udp.rb:118:in `inputworker'", "/usr/share/logstash/vendor/bundle/jruby/1.9/gems/logstash-input-udp-3.1.0/lib/logstash/inputs/udp.rb:89:in `udp_listener'"]}
09:10:47.014 [#, "backtrace"=>["/usr/share/logstash/vendor/bundle/jruby/1.9/gems/logstash-codec-msgpack-3.0.2-java/lib/logstash/codecs/msgpack.rb:36:in `decode'", "/usr/share/logstash/vendor/bundle/jruby/1.9/gems/logstash-codec-msgpack-3.0.2-java/lib/logstash/codecs/msgpack.rb:29:in `decode'", "/usr/share/logstash/vendor/bundle/jruby/1.9/gems/logstash-input-udp-3.1.0/lib/logstash/inputs/udp.rb:118:in `inputworker'", "/usr/share/logstash/vendor/bundle/jruby/1.9/gems/logstash-input-udp-3.1.0/lib/logstash/inputs/udp.rb:89:in `udp_listener'"]}

From this point, logstash stops

The way to solve it

In the rescue part of the plain text failover, event is not set. It should be initialized if not present this way :

    rescue => e
      # Treat as plain text and try to do the best we can with it?
      @logger.warn("Trouble parsing msgpack input, falling back to plain text",
                   :input => data, :exception => e)
      event ||= LogStash::Event.new()
      event.set("message", data)
      
      tags = event.get("tags").nil? ? [] : event.get("tags") 
      tags << "_msgpackparsefailure"
      event.set("tags", tags)
    end

I can handle it if you wish.