Duplicate Metric Error when Tracing Enabled on Both WebServer and gRPC Server

[jburgess]

Environment Details

• Helidon Version: 2.5.5
• Helidon SE
• JDK version: 17
• OS: Any

---

Problem Description

I am experiencing an issue when attempting to add Tracing to both the WebServer and gRPC Server in my Helidon application, which is configured with MetricsSupport. When I try to configure tracing for both servers, I receive the following error. It is worth noting that this error does not occur if I only configure Tracing for one server with .tracer(tracer).

Exception in thread "main" java.lang.RuntimeException: No reflection exceptions should be thrown unless there is a fundamental error in your code set up.
	at io.jaegertracing.internal.metrics.Metrics.createMetrics(Metrics.java:76)
	at io.jaegertracing.internal.metrics.Metrics.<init>(Metrics.java:32)
	at io.jaegertracing.internal.metrics.Metrics.<init>(Metrics.java:28)
	at io.jaegertracing.Configuration.getTracerBuilder(Configuration.java:229)
	at io.helidon.tracing.jaeger.JaegerTracerBuilder.build(JaegerTracerBuilder.java:456)
	at io.helidon.tracing.jaeger.JaegerTracerBuilder.build(JaegerTracerBuilder.java:153)
	at io.helidon.common.Builder.get(Builder.java:41)
	at io.helidon.grpc.server.GrpcServerConfiguration$Builder.tracer(GrpcServerConfiguration.java:240)
	at com.example.tracing.Main.startServer(Main.java:71)
	at com.example.tracing.Main.main(Main.java:21)
Caused by: java.lang.IllegalArgumentException: Attempt to reregister the existing metric MetricID{name='jaeger_tracer_reporter_queue_length', tags=[]}
	at io.helidon.metrics.api.AbstractRegistry.enforceMetricUniqueness(AbstractRegistry.java:713)
	at io.helidon.metrics.api.AbstractRegistry.enforceMetricUniqueness(AbstractRegistry.java:708)
	at io.helidon.metrics.api.AbstractRegistry.registerUniqueMetric(AbstractRegistry.java:668)
	at io.helidon.metrics.api.AbstractRegistry.register(AbstractRegistry.java:118)
	at io.helidon.metrics.jaeger.HelidonJaegerMetricsFactory$3.<init>(HelidonJaegerMetricsFactory.java:88)
	at io.helidon.metrics.jaeger.HelidonJaegerMetricsFactory.createGauge(HelidonJaegerMetricsFactory.java:82)
	at io.jaegertracing.internal.metrics.Metrics.createMetrics(Metrics.java:66)
	... 9 more

Steps to reproduce

This error can be reproduced with the following Java code:

    LogConfig.configureRuntime();

    var config = Config.create();

    var metrics = MetricsSupport.create();

    var tracer = TracerBuilder.create(config.get("tracing"));

    var simpleGreetService = new SimpleGreetService(config);
    var builder = Routing.builder()
        .register("/simple-greet", simpleGreetService);

    var health = HealthSupport.builder().addLiveness(HealthChecks.healthChecks()).build();
    var adminRouting = Routing.builder()
        .register(health)
        .register(metrics)
        .register(WebTracingConfig.create(config.get("tracing")))
        .build();

    // Web Server
    var server = WebServer.builder(builder)
        .tracer(tracer)
        .addNamedRouting("admin", adminRouting)
        .config(config.get("server"))
        .build();

    var webserver = server.start();
    webserver.thenAccept(ws -> ws.whenShutdown().thenRun(() -> System.out.println("WEB server is DOWN. Good bye!")))
        .exceptionallyAccept(t -> t.printStackTrace(System.err));

    // gRPC Server
    var tracingConfig = GrpcTracingConfig.builder()
        .withStreaming()
        .withVerbosity()
        .withTracedAttributes(ServerRequestAttribute.CALL_ATTRIBUTES,
            ServerRequestAttribute.HEADERS, ServerRequestAttribute.METHOD_NAME)
        .build();

    var grpcServerConfig =
        GrpcServerConfiguration.builder(config.get("grpc"))
            .tracer(tracer)
            .tracingConfig(tracingConfig)
            .build();

    var grpcRouting = GrpcRouting.builder()
        .register(new EchoService())
        .build();

    var grpcServer =
        GrpcServer.create(grpcServerConfig, grpcRouting);

    grpcServer.start().thenAccept(s -> s.whenShutdown().thenRun(() ->
        System.out.println("gRPC server is DOWN. Good bye!"))).exceptionally(t -> {
      System.out.println("Startup failed: " + t.getMessage());
      return null;
    });