I just downloaded the new logstash version (5.2.1), and after starting it I noticed a warning message saying that log4j needs to be initialized properly.
I also noticed that plugins like kafka, beats, etc, were not emitting any output log...
I used this very simple command to reproduce the problem on a Windows machine:
$ bin\logstash -e "input{beats{port=>5044}} output{stdout{}}"
Could not find log4j2 configuration at path /Downloads/logstash-5.2.1/config/log4j2.properties. Using default config which logs to console
log4j:WARN No appenders could be found for logger (io.netty.util.internal.logging.InternalLoggerFactory).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
15:52:11.185 [[main]-pipeline-manager] INFO logstash.inputs.beats - Beats inputs: Starting input listener {:address=>"0.0.0.0:5044"}
15:52:11.285 [[main]-pipeline-manager] INFO logstash.pipeline - Starting pipeline {"id"=>"main", "pipeline.workers"=>4, "pipeline.batch.size"=>125, "pipeline.batch.delay"=>5, "pipeline.max_inflight"=>500}
15:52:11.292 [[main]-pipeline-manager] INFO logstash.pipeline - Pipeline main started
15:52:11.764 [Api Webserver] INFO logstash.agent - Successfully started Logstash API endpoint {:port=>9600}
In the above example, I tested this behavior with the Beats input plugin, but this is also happening on several other plugins like kafka.
Tested on logstash 5.1.2 and everything works well: no warnings and plugins write log data correctly.
EDIT: Just tested on logstash 5.2.0, and I have the same behavior observed in 5.2.1. Log4j warnings + no logging.
Am I missing something here? Or is this something that should not happen?