Jaeger Bindings for Java OpenTracing API

This is a client side library that implements Java OpenTracing API, with Zipkin-compatible data model.

Core Modules

Click through for more detailed docs on specific modules.

• jaeger-core: the core implementation of the OpenTracing API
• jaeger-context: in-process context propagation

Add-on Modules

• jaeger-dropwizard: a feature to initialize Jaeger from Dropwizard apps (including binding to stats/metrics)
• jaeger-apachehttpclient: instrumentation for apache http clients
• jaeger-jaxrs2: instrumentation for JAXRS2 filters
• jaeger-zipkin: compatibility layer for using Jaeger tracer as Zipkin-compatible implementation

Importing Dependencies

All artifacts are published to Maven Central. Snapshot artifacts are also published to Sonatype. Follow these instructions to add the snapshot repository to your build system.

Add the required dependencies to your project. Usually, this would only be the add-ons you require. Please use the latest version:

For e.g, to depend on the core jaeger library, you'd include the following

<dependency>
    <groupId>com.uber.jaeger</groupId>
    <artifactId>jaeger-core</artifactId>
    <version>$jaegerVersion</version>
</dependency>

###Thrift version conflicts Jaeger client uses org.apache.thrift:libthrift:0.9.2. If your project depends on a different version of libthrift, it is recommended that you use the shaded jaeger-thrift jar we publish which packages it's own libthrift.

To depend on the shaded jar, add the following to your maven build. Note that this is only supported for a jaeger version >= 0.15.0

<dependencyManagement>
  <dependencies>
    <dependency>
      <groupId>com.uber.jaeger</groupId>
      <artifactId>jaeger-thrift</artifactId>
      <classifier>thrift92</classifier>
      <version>$jaegerVersion</version>
    </dependency>
  </dependencies>
</dependencyManagement>

In-process Context Propagation

jaeger-context defines ThreadLocalTraceContext implementation of TraceContext that can be used for propagating the current tracing Span throughout the application without changing the application's code. However, if the application is starting new threads or is using thread pools, the thread-local context is not going to be carried over into the execution in the next thread. To maintain context propagation, a wrapper TracedExecutorService is provided that automatically transfers the context onto the new threads.

ExecutorService instrumentedExecutorService = TracingUtils.tracedExecutor(wrappedExecutorService);

Testing

When testing tracing instrumentation it is often useful to make sure that all spans are being captured, which is not the case in production configurations where heavy sampling is applied by default. The following configuration can be provided to affect which sampling is applied to the new traces:

sampler:
   type: const # can either be const, probabilistic, or ratelimiting
   param: 1  # can either be an integer, a double, or an integer

The valid values for type are:

• const: configures a sampler that always makes the same decision for new traces depending on the param: always no for param=0, always yes otherwise.
• probabilistic: configures a sampler that samples traces with probability equal to param (must be between 0.0 and 1.0)
• ratelimiting: configures a samlper that samples traces with a certain rate per second equal to param

Debug Traces (Forced Sampling)

Programmatically

The OpenTracing API defines a sampling.priority standard tag that can be used to affect the sampling of a span and its children:

import io.opentracing.tag.Tags;

Tags.SAMPLING_PRIORITY.set(span, (short) 1);

Via HTTP Headers

Jaeger Tracer also understands a special HTTP Header jaeger-debug-id, which can be set in the incoming request, e.g.

curl -H "jaeger-debug-id: some-correlation-id" http://myhost.com

When Jaeger sees this header in the request that otherwise has no tracing context, it ensures that the new trace started for this request will be sampled in the "debug" mode (meaning it should survive all downsampling that might happen in the collection pipeline), and the root span will have a tag as if this statement was executed:

span.setTag("jaeger-debug-id", "some-correlation-id")

This allows using Jaeger UI to find the trace by this tag.

Developing

1. git submodule init update
2. ./gradlew googleJavaFormat clean test

Code Style

This project uses google java style. It is recommended to set up a git precommit hook as follows.

cat>.git/hooks/pre-commit
#!/bin/sh
#
# Pre-commit hooks
# Format code using the google formatter
echo "pre-commit code format"
./gradlew googleJavaFormat
^D

chmod a+x .git/hooks/pre-commit

You can also setup the IntelliJ plugin to reformat code from within your IDE

Lombok

This project uses Lombok to reduce boilerplate. You can setup the IntelliJ plugin to add IDE support.

License

The MIT License.