Skip to content

Latest commit

 

History

History
92 lines (68 loc) · 3.44 KB

03-initialize-real-tracer.md

File metadata and controls

92 lines (68 loc) · 3.44 KB
Raw

Let's create an instance of a real tracer, such as Jaeger (https://github.com/uber/jaeger-client-java). Our pom.xml already imports Jaeger:

<dependency>
    <groupId>io.jaegertracing</groupId>
    <artifactId>jaeger-client</artifactId>
    <version>0.32.0</version>
</dependency>

We need to add some imports:

import io.jaegertracing.Configuration;
import io.jaegertracing.Configuration.ReporterConfiguration;
import io.jaegertracing.Configuration.SamplerConfiguration;
import io.jaegertracing.internal.JaegerTracer;

And we define a helper function that will create a tracer.

public static JaegerTracer initTracer(String service) {
    SamplerConfiguration samplerConfig = new SamplerConfiguration().fromEnv().withType("const").withParam(1);
    ReporterConfiguration reporterConfig = new ReporterConfiguration().fromEnv().withLogSpans(true);
    Configuration config = new Configuration(service).withSampler(samplerConfig).withReporter(reporterConfig);
    return config.getTracer();
}

To use this instance, let's change the main function:

Tracer tracer = initTracer("hello-world");
new Hello(tracer).sayHello(helloTo);

Note that we are passing a string hello-world to the init method. It is used to mark all spans emitted by the tracer as originating from a hello-world service.

This is how our Hello class looks like now:

package lesson01.exercise;

import io.opentracing.Span;
import io.opentracing.Tracer;
import io.opentracing.util.GlobalTracer;

import io.jaegertracing.Configuration;
import io.jaegertracing.Configuration.ReporterConfiguration;
import io.jaegertracing.Configuration.SamplerConfiguration;
import io.jaegertracing.internal.JaegerTracer;

public class Hello {

    private final Tracer tracer;

    private Hello(Tracer tracer) {
        this.tracer = tracer;
    }

    private void sayHello(String helloTo) {
        Span span = tracer.buildSpan("say-hello").start();

        String helloStr = String.format("Hello, %s!", helloTo);
        System.out.println(helloStr);

        span.finish();
    }

    public static void main(String[] args) {
        if (args.length != 1) {
            throw new IllegalArgumentException("Expecting one argument");
        }
        String helloTo = args[0];
        Tracer tracer = initTracer("hello-world");
        new Hello(tracer).sayHello(helloTo);
    }

    public static JaegerTracer initTracer(String service) {
        SamplerConfiguration samplerConfig = new SamplerConfiguration().fromEnv().withType("const").withParam(1);
        ReporterConfiguration reporterConfig = new ReporterConfiguration().fromEnv().withLogSpans(true);
        Configuration config = new Configuration(service).withSampler(samplerConfig).withReporter(reporterConfig);
        return config.getTracer();
    }

}

NOTE: as this scenario runs on Docker, we need to specify the Agent's hostname to the Jaeger client. We can do that by setting this: export JAEGER_ENDPOINT=http://host01:14268/api/traces{{execute}}.

Running the program now, we see a span logged. Try it out: ./run.sh lesson01.exercise.Hello Bryan{{execute}}.

Check also the Jaeger UI for the newly created trace!