test(o11y): add showcase test for golden signals metrics

Added `ITOtelGoldenMetrics` alongside `ITOtelTracing` to ensure that Golden Signals are correctly collected with accurate dimensional attributes (e.g., service name, status code, error type, port, addressing) across both the gRPC and HTTP/JSON runtime transports.

Author: blakeli0

sdk-platform-java/java-showcase/gapic-showcase/src/test/java/com/google/showcase/v1beta1/it/ITOtelGoldenMetrics.java

@@ -0,0 +1,377 @@
+/*
+ * Copyright 2026 Google LLC
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google LLC nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package com.google.showcase.v1beta1.it;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.junit.Assert.assertThrows;
+
+import com.google.api.client.http.HttpTransport;
+import com.google.api.gax.core.NoCredentialsProvider;
+import com.google.api.gax.rpc.StatusCode;
+import com.google.api.gax.rpc.TransportChannelProvider;
+import com.google.api.gax.rpc.UnavailableException;
+import com.google.api.gax.tracing.GoldenSignalsMetricsTracerFactory;
+import com.google.api.gax.tracing.ObservabilityAttributes;
+import com.google.common.collect.ImmutableList;
+import com.google.rpc.Status;
+import com.google.showcase.v1beta1.EchoClient;
+import com.google.showcase.v1beta1.EchoRequest;
+import com.google.showcase.v1beta1.EchoSettings;
+import com.google.showcase.v1beta1.it.util.TestClientInitializer;
+import com.google.showcase.v1beta1.stub.EchoStubSettings;
+import io.grpc.CallOptions;
+import io.grpc.Channel;
+import io.grpc.ClientCall;
+import io.grpc.ClientInterceptor;
+import io.grpc.MethodDescriptor;
+import io.grpc.Metadata;
+import io.opentelemetry.api.common.AttributeKey;
+import io.opentelemetry.sdk.OpenTelemetrySdk;
+import io.opentelemetry.sdk.metrics.SdkMeterProvider;
+import io.opentelemetry.sdk.metrics.data.MetricData;
+import io.opentelemetry.sdk.testing.exporter.InMemoryMetricReader;
+import java.io.ByteArrayInputStream;
+import java.io.InputStream;
+import java.util.Collection;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+class ITOtelGoldenMetrics {
+  private static final String SHOWCASE_SERVER_ADDRESS = "localhost";
+  private static final long SHOWCASE_SERVER_PORT = 7469;
+  private static final String SHOWCASE_ARTIFACT = "com.google.cloud:gapic-showcase";
+
+  private InMemoryMetricReader metricReader;
+  private OpenTelemetrySdk openTelemetrySdk;
+
+  @BeforeEach
+  void setup() {
+    metricReader = InMemoryMetricReader.create();
+
+    SdkMeterProvider meterProvider =
+        SdkMeterProvider.builder().registerMetricReader(metricReader).build();
+
+    openTelemetrySdk = OpenTelemetrySdk.builder().setMeterProvider(meterProvider).build();
+  }
+
+  @AfterEach
+  void tearDown() {
+    if (openTelemetrySdk != null) {
+      openTelemetrySdk.close();
+    }
+  }
+
+  @Test
+  void testMetrics_successfulEcho_grpc() throws Exception {
+    GoldenSignalsMetricsTracerFactory tracerFactory =
+        new GoldenSignalsMetricsTracerFactory(openTelemetrySdk);
+
+    try (EchoClient client =
+        TestClientInitializer.createGrpcEchoClientOpentelemetry(tracerFactory)) {
+
+      client.echo(EchoRequest.newBuilder().setContent("metrics-test").build());
+
+      Collection<MetricData> metrics = metricReader.collectAllMetrics();
+      assertThat(metrics).isNotEmpty();
+
+      MetricData durationMetric =
+          metrics.stream()
+              .filter(m -> m.getName().equals("gcp.client.request.duration"))
+              .findFirst()
+              .orElseThrow(() -> new AssertionError("Duration metric not found"));
+
+      assertThat(durationMetric.getInstrumentationScopeInfo().getName())
+          .isEqualTo(SHOWCASE_ARTIFACT);
+      assertThat(durationMetric.getInstrumentationScopeInfo().getVersion())
+          .isEqualTo(com.google.api.gax.core.GaxProperties.getLibraryVersion(EchoClient.class));
+
+      io.opentelemetry.api.common.Attributes attributes =
+          durationMetric.getHistogramData().getPoints().iterator().next().getAttributes();
+
+      assertThat(
+              attributes.get(AttributeKey.stringKey(ObservabilityAttributes.SERVER_ADDRESS_ATTRIBUTE)))
+          .isEqualTo(SHOWCASE_SERVER_ADDRESS);
+      assertThat(
+              attributes.get(AttributeKey.longKey(ObservabilityAttributes.SERVER_PORT_ATTRIBUTE)))
+          .isEqualTo(SHOWCASE_SERVER_PORT);
+      assertThat(
+              attributes.get(AttributeKey.stringKey(ObservabilityAttributes.RPC_SYSTEM_NAME_ATTRIBUTE)))
+          .isEqualTo("grpc");
+      assertThat(
+              attributes.get(AttributeKey.stringKey(ObservabilityAttributes.GCP_CLIENT_SERVICE_ATTRIBUTE)))
+          .isEqualTo("showcase");
+      assertThat(
+              attributes.get(AttributeKey.stringKey(ObservabilityAttributes.GRPC_RPC_METHOD_ATTRIBUTE)))
+          .isEqualTo("google.showcase.v1beta1.Echo/Echo");
+      assertThat(
+              attributes.get(AttributeKey.stringKey(ObservabilityAttributes.RPC_RESPONSE_STATUS_ATTRIBUTE)))
+          .isEqualTo("OK");
+    }
+  }
+
+  @Test
+  void testMetrics_failedEcho_grpc_recordsErrorType() throws Exception {
+    GoldenSignalsMetricsTracerFactory tracerFactory =
+        new GoldenSignalsMetricsTracerFactory(openTelemetrySdk);
+
+    ClientInterceptor interceptor =
+        new ClientInterceptor() {
+          @Override
+          public <ReqT, RespT> ClientCall<ReqT, RespT> interceptCall(
+              MethodDescriptor<ReqT, RespT> method, CallOptions callOptions, Channel next) {
+            return new ClientCall<ReqT, RespT>() {
+              @Override
+              public void start(Listener<RespT> responseListener, Metadata headers) {
+                responseListener.onClose(io.grpc.Status.UNAVAILABLE, new Metadata());
+              }
+
+              @Override
+              public void request(int numMessages) {}
+
+              @Override
+              public void cancel(String message, Throwable cause) {}
+
+              @Override
+              public void halfClose() {}
+
+              @Override
+              public void sendMessage(ReqT message) {}
+            };
+          }
+        };
+
+    TransportChannelProvider transportChannelProvider =
+        EchoSettings.defaultGrpcTransportProviderBuilder()
+            .setChannelConfigurator(io.grpc.ManagedChannelBuilder::usePlaintext)
+            .setInterceptorProvider(() -> ImmutableList.of(interceptor))
+            .build();
+
+    try (EchoClient client =
+        TestClientInitializer.createGrpcEchoClientOpentelemetry(
+            tracerFactory, transportChannelProvider)) {
+
+      assertThrows(
+          UnavailableException.class,
+          () -> client.echo(EchoRequest.newBuilder().setContent("metrics-test").build()));
+
+      Collection<MetricData> metrics = metricReader.collectAllMetrics();
+      assertThat(metrics).isNotEmpty();
+
+      MetricData durationMetric =
+          metrics.stream()
+              .filter(m -> m.getName().equals("gcp.client.request.duration"))
+              .findFirst()
+              .orElseThrow(() -> new AssertionError("Duration metric not found"));
+
+      io.opentelemetry.api.common.Attributes attributes =
+          durationMetric.getHistogramData().getPoints().iterator().next().getAttributes();
+
+      assertThat(
+              attributes.get(AttributeKey.stringKey(ObservabilityAttributes.RPC_RESPONSE_STATUS_ATTRIBUTE)))
+          .isEqualTo("UNAVAILABLE");
+      assertThat(
+              attributes.get(AttributeKey.stringKey(ObservabilityAttributes.ERROR_TYPE_ATTRIBUTE)))
+          .isEqualTo("UNAVAILABLE");
+    }
+  }
+
+  @Test
+  void testMetrics_successfulEcho_httpjson() throws Exception {
+    GoldenSignalsMetricsTracerFactory tracerFactory =
+        new GoldenSignalsMetricsTracerFactory(openTelemetrySdk);
+
+    try (EchoClient client =
+        TestClientInitializer.createHttpJsonEchoClientOpentelemetry(tracerFactory)) {
+
+      client.echo(EchoRequest.newBuilder().setContent("metrics-test").build());
+
+      Collection<MetricData> metrics = metricReader.collectAllMetrics();
+      assertThat(metrics).isNotEmpty();
+
+      MetricData durationMetric =
+          metrics.stream()
+              .filter(m -> m.getName().equals("gcp.client.request.duration"))
+              .findFirst()
+              .orElseThrow(() -> new AssertionError("Duration metric not found"));
+
+      assertThat(durationMetric.getInstrumentationScopeInfo().getName())
+          .isEqualTo(SHOWCASE_ARTIFACT);
+      assertThat(durationMetric.getInstrumentationScopeInfo().getVersion())
+          .isEqualTo(com.google.api.gax.core.GaxProperties.getLibraryVersion(EchoClient.class));
+
+      io.opentelemetry.api.common.Attributes attributes =
+          durationMetric.getHistogramData().getPoints().iterator().next().getAttributes();
+
+      assertThat(
+              attributes.get(AttributeKey.stringKey(ObservabilityAttributes.SERVER_ADDRESS_ATTRIBUTE)))
+          .isEqualTo(SHOWCASE_SERVER_ADDRESS);
+      assertThat(
+              attributes.get(AttributeKey.longKey(ObservabilityAttributes.SERVER_PORT_ATTRIBUTE)))
+          .isEqualTo(SHOWCASE_SERVER_PORT);
+      assertThat(
+              attributes.get(AttributeKey.stringKey(ObservabilityAttributes.RPC_SYSTEM_NAME_ATTRIBUTE)))
+          .isEqualTo("http");
+      assertThat(
+              attributes.get(AttributeKey.stringKey(ObservabilityAttributes.GCP_CLIENT_SERVICE_ATTRIBUTE)))
+          .isEqualTo("showcase");
+      assertThat(
+              attributes.get(AttributeKey.stringKey(ObservabilityAttributes.RPC_RESPONSE_STATUS_ATTRIBUTE)))
+          .isEqualTo("OK");
+      assertThat(
+              attributes.get(AttributeKey.longKey(ObservabilityAttributes.HTTP_RESPONSE_STATUS_ATTRIBUTE)))
+          .isEqualTo(200L);
+      assertThat(
+              attributes.get(AttributeKey.stringKey(ObservabilityAttributes.URL_TEMPLATE_ATTRIBUTE)))
+          .isEqualTo("v1beta1/echo:echo");
+      assertThat(
+              attributes.get(AttributeKey.stringKey(ObservabilityAttributes.GRPC_RPC_METHOD_ATTRIBUTE)))
+          .isNull(); 
+    }
+  }
+
+  @Test
+  void testMetrics_failedEcho_httpjson_recordsErrorType() throws Exception {
+    GoldenSignalsMetricsTracerFactory tracerFactory =
+        new GoldenSignalsMetricsTracerFactory(openTelemetrySdk);
+
+    HttpTransport mockTransport =
+        new HttpTransport() {
+          @Override
+          protected com.google.api.client.http.LowLevelHttpRequest buildRequest(
+              String method, String url) {
+            return new com.google.api.client.http.LowLevelHttpRequest() {
+              @Override
+              public void addHeader(String name, String value) {}
+
+              @Override
+              public com.google.api.client.http.LowLevelHttpResponse execute() {
+                return new com.google.api.client.http.LowLevelHttpResponse() {
+                  @Override
+                  public InputStream getContent() {
+                    return new ByteArrayInputStream("{}".getBytes());
+                  }
+
+                  @Override
+                  public String getContentEncoding() {
+                    return null;
+                  }
+
+                  @Override
+                  public long getContentLength() {
+                    return 2;
+                  }
+
+                  @Override
+                  public String getContentType() {
+                    return "application/json";
+                  }
+
+                  @Override
+                  public String getStatusLine() {
+                    return "HTTP/1.1 503 Service Unavailable";
+                  }
+
+                  @Override
+                  public int getStatusCode() {
+                    return 503;
+                  }
+
+                  @Override
+                  public String getReasonPhrase() {
+                    return "Service Unavailable";
+                  }
+
+                  @Override
+                  public int getHeaderCount() {
+                    return 0;
+                  }
+
+                  @Override
+                  public String getHeaderName(int index) {
+                    return null;
+                  }
+
+                  @Override
+                  public String getHeaderValue(int index) {
+                    return null;
+                  }
+                };
+              }
+            };
+          }
+        };
+
+    EchoSettings httpJsonEchoSettings =
+        EchoSettings.newHttpJsonBuilder()
+            .setCredentialsProvider(NoCredentialsProvider.create())
+            .setTransportChannelProvider(
+                EchoSettings.defaultHttpJsonTransportProviderBuilder()
+                    .setHttpTransport(mockTransport)
+                    .setEndpoint(TestClientInitializer.DEFAULT_HTTPJSON_ENDPOINT)
+                    .build())
+            .build();
+
+    EchoStubSettings echoStubSettings =
+        (EchoStubSettings)
+            httpJsonEchoSettings.getStubSettings().toBuilder()
+                .setTracerFactory(tracerFactory)
+                .build();
+
+    try (EchoClient client = EchoClient.create(echoStubSettings.createStub())) {
+      assertThrows(
+          UnavailableException.class,
+          () -> client.echo(EchoRequest.newBuilder().setContent("metrics-test").build()));
+
+      Collection<MetricData> metrics = metricReader.collectAllMetrics();
+      assertThat(metrics).isNotEmpty();
+
+      MetricData durationMetric =
+          metrics.stream()
+              .filter(m -> m.getName().equals("gcp.client.request.duration"))
+              .findFirst()
+              .orElseThrow(() -> new AssertionError("Duration metric not found"));
+
+      io.opentelemetry.api.common.Attributes attributes =
+          durationMetric.getHistogramData().getPoints().iterator().next().getAttributes();
+
+      assertThat(
+              attributes.get(AttributeKey.stringKey(ObservabilityAttributes.RPC_RESPONSE_STATUS_ATTRIBUTE)))
+          .isEqualTo("UNAVAILABLE");
+      assertThat(
+              attributes.get(AttributeKey.longKey(ObservabilityAttributes.HTTP_RESPONSE_STATUS_ATTRIBUTE)))
+          .isEqualTo(503L);
+      assertThat(
+              attributes.get(AttributeKey.stringKey(ObservabilityAttributes.ERROR_TYPE_ATTRIBUTE)))
+          .isEqualTo("503");
+    }
+  }
+}