The OpenCensus Agent for Java collects and sends latency data about your Java process to OpenCensus backends such as Zipkin, Stackdriver Trace, etc. for analysis and visualization.
The OpenCensus Agent for Java is in an early development stage. The following features are currently implemented:
TODO(stschmidt): Update README.md along with implementation.
We see tracing as a cross-cutting concern which the OpenCensus Agent for Java weaves into existing Java bytecode (the application and its libraries) at runtime, typically when first loading the concerned bytecode.
This approach allows us to instrument arbitrary code without having to touch the source code of the application or its dependencies. Furthermore, we don‘t require the application owner to upgrade any of the application’s third-party dependencies to specific versions. As long as the interface (e.g. java.sql.Driver#connect) stays as-is across the supported versions, the Java agent's bytecode weaver will be able to instrument the code.
The OpenCensus Agent for Java uses Byte Buddy, a widely used and well-maintained bytecode manipulation library, for instrumenting selected Java methods at class load-time. Which Java methods we want to intercept/instrument obviously depends on the library (MongoDB vs. Redis, etc.) and the application.
To enable the OpenCensus Agent for Java for your application, add the option -javaagent:path/to/opencensus-agent.jar to the invocation of the java executable as shown in the following example:
java -javaagent:path/to/opencensus-agent.jar ...