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Core

This module provides core tracing functionality for custom instrumentation.

Maven coordinates

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

Usage

Production

Tracer can be created via com.uber.jaeger.Tracer.Builder or com.uber.jaeger.Configuration. For production it is recommended to use both classes with default values.

Tracer.Builder example:

Tracer tracer = new Tracer.Builder("myServiceName")
  .build()

Configuration holds only primitive values and it is designed to be used with configuration files or when configuration is provided in environmental variables.

Configuration config = new Configuration("myServiceName")
  .withReporter(...); // optional if you want to get metrics about tracer behavior

Tracer tracer = config.getTracer();

The config objects lazily builds and configures Jaeger Tracer. Multiple calls to getTracer() return the same instance.

Configuration via Environment

It is also possible to obtain a com.uber.jaeger.Configuration object configured using properties specified as environment variables or system properties. A value specified as a system property will override a value specified as an environment variable for the same property name.

Configuration config = Configuration.fromEnv();

The property names are:

Property Required Description
JAEGER_SERVICE_NAME yes The service name
JAEGER_AGENT_HOST no The hostname for communicating with agent via UDP
JAEGER_AGENT_PORT no The port for communicating with agent via UDP
JAEGER_ENDPOINT no The traces endpoint, in case the client should connect directly to the Collector, like http://jaeger-collector:14268/api/traces
JAEGER_AUTH_TOKEN no Authentication Token to send as "Bearer" to the endpoint
JAEGER_USER no Username to send as part of "Basic" authentication to the endpoint
JAEGER_PASSWORD no Password to send as part of "Basic" authentication to the endpoint
JAEGER_PROPAGATION no Comma separated list of formats to use for propagating the trace context. Defaults to the standard Jaeger format. Valid values are jaeger and b3
JAEGER_REPORTER_LOG_SPANS no Whether the reporter should also log the spans
JAEGER_REPORTER_MAX_QUEUE_SIZE no The reporter's maximum queue size
JAEGER_REPORTER_FLUSH_INTERVAL no The reporter's flush interval (ms)
JAEGER_SAMPLER_TYPE no The sampler type
JAEGER_SAMPLER_PARAM no The sampler parameter (number)
JAEGER_SAMPLER_MANAGER_HOST_PORT no The host name and port when using the remote controlled sampler
JAEGER_TAGS no A comma separated list of name = value tracer level tags, which get added to all reported spans. The value can also refer to an environment variable using the format ${envVarName:default}, where the :default is optional, and identifies a value to be used if the environment variable cannot be found

Setting JAEGER_AGENT_HOST/JAEGER_AGENT_PORT will make the client send traces to the agent via UdpSender. If the JAEGER_ENDPOINT environment variable is also set, the traces are sent to the endpoint, effectively making the JAEGER_AGENT_* vars ineffective.

When the JAEGER_ENDPOINT is set, the HttpSender is used when submitting traces to a remote endpoint, usually served by a Jaeger Collector. If the endpoint is secured, a HTTP Basic Authentication can be performed by setting the related environment vars. Similarly, if the endpoint expects an authentication token, like a JWT, set the JAEGER_AUTH_TOKEN environment variable. If the Basic Authentication environment variables and the Auth Token environment variable are set, Basic Authentication is used.

Obtaining Tracer via TracerResolver

Jaeger's Java Client also provides an implementation of the TracerResolver, allowing a Tracer to be obtained in a vendor neutral manner. This TracerResolver implementation uses the configuration via environment approach described above.

More information about using the TracerResolver can be found here.

Reporting internal metrics via Micrometer

The Jaeger Java Client collects internal metrics and is able to report them via Micrometer. To accomplish that, include the artifact com.uber.jaeger:jaeger-micrometer as a dependency to your project and use MicrometerMetricsFactory like this:

MicrometerMetricsFactory metricsReporter = new MicrometerMetricsFactory();
Configuration configuration = new Configuration("myServiceName");
Tracer tracer = configuration
    .getTracerBuilder()
    .withMetrics(new com.uber.jaeger.metrics.Metrics(metricsReporter))
    .build();

Development

The last two parameters to new Configuration() allow control over configuration of the Sampler and Reporter. However, especially in unit tests, it's useful to have tracer that is not connected to tracing backend, but collects spans in memory:

Reporter reporter = new InMemoryReporter();
Sampler sampler = new ConstSampler(true);
Tracer tracer = new Tracer.Builder(serviceName)
    .withReporter(reporter)
    .withSampler(sampler)
    .build();

See also: opentracing-java