tracker2.trackers >> [tracker3]
        tracker3.trackers >> []

        def generator = new ClientBuildEventGenerator(consumer, subscriptions, [mapper], fallback)

        when:
        generator.started(operation, startEvent)

        then:
        1 * tracker1.started(operation, startEvent)
        1 * tracker2.started(operation, startEvent)

									// the OTel collector exports to Zipkin
									traces, err := tracing.GetZipkinInstance().QueryTraces(300, "", tc.customAttribute)
									t.Logf("got traces %v from %s", traces, cluster)
									if err != nil {
										return fmt.Errorf("cannot get traces from zipkin: %v", err)
									}
									if !tracing.VerifyOtelEchoTraces(ctx, appNsInst.Name(), cluster.Name(), traces) {
										return errors.New("cannot find expected traces")

    val tracer = this.tracer
    return if (tracer == null) {
        writeAction()
    } else {
        val frameName = name()
        try {
            tracer.open(frameName)
            writeAction()
        } finally {
            tracer.close(frameName)
        }
    }

trace, but with the `.go` extension removed.

## Trace test programs

The trace test programs in the `testprog` directory generate traces to
stdout.
Otherwise they're just normal programs.

## Trace debug commands

The `cmd` directory contains helpful tools for debugging traces.

* `gotraceraw` parses traces without validation.
  It can produce a text version of the trace wire format, or convert

import java.util.Collections;
import java.util.List;

/**
 * Tracks some state for build operations of a given type.
 */
public interface BuildOperationTracker {
    /**
     * Returns the trackers that are used by this tracker. If this tracker is required, then its trackers should be notified of
     * build operation execution. If this tracker is not required, the trackers can be ignored.
     */

					// strings were generated by
					// runtime/trace.TestUserTaskRegion, which is the basis for
					// the user_task_region_* test cases. We only check for the
					// Go 1.21 traces because earlier traces used different
					// strings.
					switch ev.Kind() {
					case trace.EventRegionBegin, trace.EventRegionEnd:
						if _, ok := validRegions[ev.Region().Type]; !ok {

						}
						traces, err := tracing.GetZipkinInstance().QueryTraces(300,
							fmt.Sprintf("server.%s.svc.cluster.local:80/*", appNsInst.Name()), "")
						if err != nil {
							return fmt.Errorf("cannot get traces from zipkin: %v", err)
						}
						if !tracing.VerifyEchoTraces(t, appNsInst.Name(), cluster.Name(), traces) {
							return errors.New("cannot find expected traces")
						}
						return nil

traces: {
  key: "x@"
  value: {
    file_line_cols: {
      line: 1
      col:  1
    }
  }
}
traces: {
  key: "x_y_sum@"
  value: {
    file_line_cols: {
      line: 3
      col:  1
    }
    file_line_cols: {
      line: 4
      col:  1
    }
  }
}
traces: {
  key: "y@"
  value: {
    file_line_cols: {
      line: 2

    boolean isEnabled(BuildEventSubscriptions subscriptions);

    Class<DETAILS> getDetailsType();

    /**
     * Returns the trackers that are used by this mapper. If this mapper is enabled, then the trackers should be notified of
     * build operation execution. If this mapper is not enabled, the trackers can be ignored.
     */
    default List<? extends BuildOperationTracker> getTrackers() {
        return Collections.emptyList();
    }

	// can be used across trace enable/disable boundaries,
	// which complicates the problem.
	//
	// For example, consider the following scenario:
	//   - trace is enabled.
	//   - trace.WithRegion is called, so a new context ctx
	//     with a new region is created.
	//   - trace is disabled.
	//   - trace is enabled again.
	//   - trace APIs with the ctx is called. Is the ID in the task