JVM breakglass

Using a Clojure REPL to troubleshoot live Java/JVM processes

Author: Mathieu Gauthron

http://slides-euroclojure2014.matlux.net

Before I start, follow this link to get the slides of the presentation.(pause) (Ok, let's start) See this image? Who recognises this sign? (pause) Normally when you press on it it's because there is fire! (pause) Here imagine the same but when you JVM process is on fire. (pause) When it happens you might want to use this freely available tool to track down the issue that is causing it. (pause) I have developed and used this tool successfully on many projects before. Today I'm here to demonstrate how JVM-breakglass can be used to debug a pure Java Application with (what some Java developers might see as) a bit of magic. (pause) BTW, My name is MG. (p) I worn many hats. (p) Currently I have the sexiest job in the world: DEvOPs in an Investment bank. (total time 1 min)

Agenda

Traditional troubleshooting of a Java application
What is JVM-breakglass?
How does JVM-breakglass work?
How to integrate it in an application?
Live Debugging demo

Troubleshooting a Java application

Debugger
Log/print statements
JMX
Adhoc interactive mechanism

What is JVM-breakglass?

Open Source Maven Library
Integrated on any JVM process
Console onto a JVM process

What are the main JVM-breakglass features?

Interactive prompt
See inside private members
Call arbitrary methods
Creation of new object instances
Creation of new classes
Monitor object state
No need to use Clojure to develop the application

How does it work?

Time for a...

Enterprise Application Diagram

http://localhost:8080/SpringMVC/city

Let's take a step back

Interactive prompt
Full JVM introspection
Access private/public members, methods, fields...
Call arbitrary methods
Monitor object state
Creation of new object instances
Overwrite class definition on the fly
No Clojure inside the Java project

github: https://github.com/matlux/jvm-breakglass

blog: http://www.matlux.net

Twitter: @matluxian