rust-jvmti

An extensible, safe native JVM agent implemented in pure Rust.

A word of warning

This project is far from being complete or usable to say the least and contains a healthy dose of proof-of-concept code that is guaranteed to either work or not.

Abstract

Rust JVMTI (yeah, it deserves a better name) is intended to become a slim JVM application performance management (APM) tool leveraging both safe access to native JVM functionality via Rust and byte code instrumentation using Java code.

Already implemented (probably poorly)

• Ability to connect to a JVM as a native agent library
• Read and parse loaded class files
• Generate byte code from loaded or created class files
• Gathering and displaying statistics about method class, class loading and synchronization times
• Read basic command line configuration
• Basic JVM emulator for implementing unit tests without the need for an actual JVM

Planned features

Short(ish) term plans

• Clean the initial code design up a bit
• Make data collection and JVM callbacks work in parallel so that it doesn't block Java calls
• Higher level API for accessing JVMTI/JNI functionality
• JVM byte code instrumentation/transformation
• Dynamic tracing/profiling
• Execution path tracing
• Proper logging using the slog crate instead of dumping everything to stdout

Medium term ideas

• Some ugly but usable GUI to display the gathered statistics (I'm so bad at designing GUIs)
• Separate store for collected data
• DSL to generate custom JVM byte code in an efficient and type-safe manner
• Java source parsing and AST support

Long term ideas (wishes, cough)

• Ability to trace other JVM languages (Scala, Clojure, Frege, Kotlin, etc)
• Ability to process creepy stuff like AspectJ and other BCI stuff
• Naive Java-to-native compilation (similarly to scala-native)

(to be continued...)

Usage

Just don't yet. Although the code is supposed to be safe and correct, it's highly experimental and immature in general. Loading this agent may corrupt your soul as well as your JVM but at least in a type-safe way.

If you really insist on trying this library then build it with the usual cargo build --release and fire up a Java VM with a command something like

java -agentpath:./target/release/libjvmti.so MyClass

The only supported configuration directive is agentid at the moment. This allows identifying and a specific instance more easily. Every other configuration will be passed to custom_args.