This document discusses memory and thread issues that can occur with JRuby applications and how Eclipse Memory Analyzer can help address them. It provides an overview of Ruby and JRuby, common problems like memory leaks and thread issues, and how the Memory Analyzer tool works. It then describes a JRuby extension plugin for Memory Analyzer that can produce readable Ruby stack traces from heap dumps to help debug issues. Further enhancements are discussed along with a call for feedback.

1. The Right Pill for JRuby
Memory and Thread Issues:
Eclipse Memory Analyzer
Vladimir Pavlov
Dimitar Giormov Memory Analyzer
SAP Labs Bulgaria

2. AGENDA
 Ruby and JRuby
 The Headaches
 Eclipse Memory Analyzer
 The Pill
 Further Enhancements
 Q&A
© SAP 2010 / Page 2

3. DISCLAIMER
 We are not experts in Ruby/JRuby
 Although we have (some) experience with those
 However, we have quite a lot of experience and track in Java and Eclipse
 Or at least we think so ;-)
© SAP 2010 / Page 3

4. RUBY AND JRUBY
 Ruby is…
 Dynamic scripting language
 Object-oriented
 Focus on simplicity and productivity
 Elegant syntax, natural to read and easy to write
 JRuby is…
 100% Java implementation of the Ruby programming language
 Interpreter running atop the JVM
 Generating Java bytecode (JIT compilation mode)
 Tight integration with Java
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5. THE HEADACHES
 Memory leaks
 Hard to debug and find the root cause
 Eventually lead to OOM errors
 Brings your system down
 Often not reproducible
 Thread issues
 Deadlocks
 Exhausted threads
 Waiting for an external resource – e.g. DB connection
 Application does not respond
 Whole system hangs
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6. THE HEADACHES – AGGRAVATED
Adding JRuby into the picture…
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7. ECLIPSE MEMORY ANALYZER
 Eclipse Memory Analyzer (MAT) is…
 Java heap analyzer Memory Analyzer
 Helps find memory leaks and reduce memory consumption
 Query heap dumps via OQL
 Multi-Gigabyte Java Heap Dumps Are Nothing to Fear Now
 Soooo much faster than other tools, e.g. jhat
 Very little memory “overhead” for processing heap dumps (again – cf. jhat)
 Provides a report with automatically extracted leak suspects
 Supports Sun, SAP, HP, IBM JDKs 1.4.2 and above
 Could also process thread dumps and correlate data to provide additional details
 Highly extensible
 Open source
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8. THE PILL
 JRuby extension plugin for Eclipse Memory Analyzer
 Plugs into the heap dump processing by means of extension points
<extension point="org.eclipse.mat.api.requestResolver">
<resolver
impl="org.eclipse.mat.extension.jruby.RubyStacktraceDumper">
</resolver>
<resolver
impl="org.eclipse.mat.extension.jruby.JRubyScriptResolver">
</resolver>
</extension>
 Looks for specific JRuby implementation objects in the heap
@Subject("org.jruby.internal.runtime.RubyRunnable")
@Subject("org.jruby.runtime.ThreadContext")
 Produces readable Ruby stack traces
 Memory Analyzer 1.1 snapshot/preview download
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9. FURTHER ENHANCEMENTS
 Producing hybrid Ruby/Java stack traces
 Thread dumps analysis
 Specific use case information, e.g. session data
 Automation
 …
 Feedback…
 Ideas…
 Contributions…
… always welcome! 
https://dev.eclipse.org/mailman/listinfo/mat-dev
http://www.eclipse.org/projects/project_summary.php?projectid=tools.mat
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10. © SAP 2010 / Page 10

11. THANK YOU!
Memory Analyzer
in: vpavlov
t: @giormov