JVMTI Native Agent

This Rust library implements a native agent for interacting with the JVM via the JVMTI. Currently this is used for enriching stack traces with local variables for each frame. This works by interacting with some corresponding Java code included in the rollbar-java SDK.

Using the agent

How to use the agent depends on how you invoke the JVM to start your application. In order to use a native agent you need to pass a command line argument to this invocation. The most basic usage would look like:

java -jar foo.jar -agentpath:path/to/librollbar_java_agent.dylib

However, if you are using a toolchain, such as Gradle, to manage your application then adding this command line argument might take a bit more effort to figure out where to add it. For Gradle the easiest way is to add the following to your build.gradle file:

applicationDefaultJvmArgs = ["-agentpath:path/to/"+System.mapLibraryName("rollbar_java_agent")]

Regardless of your JVM language of choice, at some level their is an invocation of the JVM and therefore there is a configuration option to pass arguments directly to the JVM.

Getting the agent library

We will attempt to distribute via the releases page pre-built versions of the agent library for various architectures. However, if you are running in an environment where one of these libraries does not work, then you can build your own as long as you can install the Rust toolchain.

Building Generically

• Install Rust: https://www.rust-lang.org/tools/install
• cargo build --release
• Get library from target/release/librollbar_java_agent.{so,dll,dylib}

Building on a Mac for Linux

In the particular case where you are using a Mac but want to build a shared library that works on Linux, you have to do a little bit of extra work. Luckily, Rust has a decent cross compilation story. The first step is adding the right target via rustup:

• rustup target add x86_64-unknown-linux-gnu

This is not enough because you need a cross compiling toolchain, in particular a linker, that does the right thing. You can get this via:

• brew tap SergioBenitez/osxct
• brew install x86_64-unknown-linux-gnu
  • You might have to run xcode-select --install first depending on your setup

Once that is setup, you can build for the specified target:

• cargo build --release --target x86_64-unknown-linux-gnu

You will find the resulting .so located at:

target/x86_64-unknown-linux-gnu/release/librollbar_java_agent.so

Debugging

If you want to see additional output from our agent, you can set the environment variable ROLLBAR_LOG to one of trace, debug, info, or warn. These will output different levels of information to standard out where your JVM process is running.