A proxy for a simple TCP protocol that records certain message-level metrics. Uses Java's non-blocking I/O building blocks in the java.nio package.

Prerequisites: the Leiningen build tool, and Java >= 7.

$> lein uberjar
$> java -Dlisten=8002 -Dforward=localhost:8001 -jar target/foo-proxy-0.1.0-SNAPSHOT-standalone.jar

Metrics can be requested by sending SIGUSR2 to the JVM process:

$> kill -s USR2 $(jps | grep foo-proxy | awk '{ print $1 }')

The JVM process will dump metrics to stdout.

SIGUSR1 was not used because it is reserved by the JVM and cannot be used in applications.

There is one flaw in the metrics processing: for sliding window metrics, requests are kept in a deque, which is never cleaned up. This will sooner or later lead to out-of-memory errors.

The deque should be cleaned up periodically, deleting events that are no longer needed.

As a stop-gap measure for testing over a longer period of time, the heap size can simply be increased:

java -Xmx=1024m ... 

Copyright © 2016 Johannes Staffans

Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.