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.
The context of the caller of Executor#execute is automatically propagated to the submitted Runnable.
The context of the caller of Thread#start is automatically propagated to the new thread.
As a proof-of-concept, the agent wraps the execution of URL#getContent in a new trace span.
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.
Download the latest version of the OpenCensus Agent for Java .jar file from Maven Central. Store it somewhere on disk.
To enable the OpenCensus Agent for Java for your application, add the option -javaagent:path/to/opencensus-contrib-agent-X.Y.Z.jar to the invocation of the java executable as shown in the following example. Replace X.Y.Z with the actual version number.
java -javaagent:path/to/opencensus-contrib-agent-X.Y.Z.jar ...
The OpenCensus Agent for Java uses Typesafe's configuration library for all user-configurable settings. Please refer to reference.conf for the available configuration knobs and their defaults.
You can override the default configuration in different ways. For example, to disable the automatic context propagation for Executors, add a system property as follows:
java -javaagent:path/to/opencensus-contrib-agent-X.Y.Z.jar \ -Dopencensus.contrib.agent.context-propagation.executor.enabled=false \ ...