Cannot see the trace data in zipkin - instrumentation

Question

I'm new to zipkin and brave api for distribute tracing. I've setup a zipkin server on my localhost listening on port 9411. I've executed below function but there is no trace data show in my zipkin server. Could someone point out what I'm missing?
public static void main(String[] args) {
Sender sender = OkHttpSender.create("http://localhost:9411/api/v1/spans");
Reporter reporter = AsyncReporter.builder(sender).build();
// Now, create a tracer with the service name you want to see in Zipkin.
Tracer tracer = Tracer.newBuilder()
.localServiceName("my-service")
.reporter(reporter)
.build();
Span twoPhase = tracer.newTrace().name("twoPhase").start();
try {
Span prepare = tracer.newChild(twoPhase.context()).name("prepare").start();
try {
System.out.print("prepare");
} finally {
prepare.finish();
}
Span commit = tracer.newChild(twoPhase.context()).name("commit").start();
try {
System.out.print("commit");
} finally {
commit.finish();
}
} finally {
twoPhase.finish();
}
}

Answer 1

It seems to be a timing issue.
If we add some delay, for instance, between children spans execution like
Thread.sleep(1);
In between
Span prepare = tracer.newChild(twoPhase.context()).name("prepare").start();
try {
System.out.print("prepare");
} finally {
prepare.finish();
}
Thread.sleep(1); // <<<
Span commit = tracer.newChild(twoPhase.context()).name("commit").start();
try {
System.out.print("commit");
} finally {
commit.finish();
}
Then we get to see spans:
I've faced something like this before when Zipkin dropped spans I was (mistakenly) assigning wrong timestamps to.
For reference and ease of reproduction: I've setup a project for reproducing this issue / "fix".