PortUnreachableException is logged as ERROR null via Log4j2

[gjakovljevic]

Having configured application to use GELF UDP transport and pointing it to a GrayLog server that is currently down produces "null" message after every attempt to send message to log server.

Messages are logged through log4j2 StatusLogger on ERROR level / there is no stack trace associated so I cannot pinpoint location in logger code that produces such message.

logstash-gelf version is 1.11.1 downloaded from Maven central repository.

Configuration is as follows:

Add graylog appender

appender.graylog2.type=Gelf
appender.graylog2.name=graylog2
appender.graylog2.host=udp:somehost.somedomain.com
appender.graylog2.port=12201
appender.graylog2.version=1.1
appender.graylog2.facility=logstash-gelf
appender.graylog2.extractStackTrace=true
appender.graylog2.filterStackTrace=true
appender.graylog2.maximumMessageSize=10485760

add graylog appender to root logger

rootLogger.appenderRef.graylog2.ref = graylog2

Steps to reproduce:

1. prepare log4j2 configuration as above / use valid hostname but use port that nothing is bound to or use real port but shutdown GrayLog instance
2. start application that should send logs to GrayLog
3. observe "ERROR null" messages in console

[mp911de]

Let me see whether I can reproduce the issue.

[mp911de]

You' see null because a PortUnreachableException is raised with no message. I will do two things here:

1. Report PortUnreachableException with a meaningful message
2. Make sure that null messages report at least the exception name