SNMP fails to handle enterpriseSpecific traps

I was watching https://logstash.jira.com/browse/LOGSTASH-1595#icft=LOGSTASH-1595 in hopes it would resolve the issue, however, it did not. I dug into this more and found that the SNMP trap input has problems if it doesn't know how to handle the trap.

In my case, I was trying to get mac address notifications - I did not copy any extra MIB files to be parsed. When the switch sends the trap logstash hard blocks and needs to be killed. Once killed the following error appears multiple times:

Failed to flush outgoing items {
:outgoing_count=>3,
:exception=>#<Encoding::UndefinedConversionError: ""\xE5"" from ASCII-8BIT to UTF-8>,
:backtrace=>[
"org/jruby/RubyString.java:7571:in `encode'",
"json/ext/GeneratorMethods.java:71:in `to_json'",
"file:/opt/logstash/logstash-1.4.0.dev-flatjar.jar!/logstash/event.rb:168:in `to_json'",
"file:/opt/logstash/logstash-1.4.0.dev-flatjar.jar!/logstash/outputs/elasticsearch.rb:322:in `flush'",
"org/jruby/RubyArray.java:1613:in `each'",
"file:/opt/logstash/logstash-1.4.0.dev-flatjar.jar!/logstash/outputs/elasticsearch.rb:310:in `flush'",
"file:/opt/logstash/logstash-1.4.0.dev-flatjar.jar!/stud/buffer.rb:219:in `buffer_flush'",
"org/jruby/RubyHash.java:1338:in `each'",
"file:/opt/logstash/logstash-1.4.0.dev-flatjar.jar!/stud/buffer.rb:216:in `buffer_flush'",
"file:/opt/logstash/logstash-1.4.0.dev-flatjar.jar!/stud/buffer.rb:193:in `buffer_flush'",
"file:/opt/logstash/logstash-1.4.0.dev-flatjar.jar!/stud/buffer.rb:112:in `buffer_initialize'",
"org/jruby/RubyKernel.java:1519:in `loop'",
"file:/opt/logstash/logstash-1.4.0.dev-flatjar.jar!/stud/buffer.rb:110:in `buffer_initialize'"],
:level=>:warn
}

In this case, the \xE5 appears to be related to the MAC address in the SNMP trap.

The trap being sent is the following information:

Operation: Deleted Vlan: 1 MAC Addr: 0009.0fe5.9967 Dot1dBasePort: 31

Attaching the pcap of some traps. Packet 4 triggers the error.

At the very least, logstash should handle the error without blocking, dropping the message with a non-critical error.