fix: fix exporting grpc metrics (googleapis#13376)

Author: mutianf

java-bigtable/google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/internal/csm/MetricsImpl.java

@@ -87,6 +87,7 @@
 public class MetricsImpl implements Metrics, Closeable {
 
   public static final String CUSTOM_METRIC = "bigtable.internal.enable-custom-metric";
+  public static final String CUSTOM_METRIC_PREFIX = "bigtable.custom";
 
   private static final boolean enableCustomMetric =
       Optional.ofNullable(System.getProperty(CUSTOM_METRIC))
@@ -319,7 +320,13 @@ public static OpenTelemetrySdk createBuiltinOtel(
         new BigtablePeriodicReader(
             new BigtableFilteringExporter(
                 exporter,
-                input -> input.getName().startsWith("bigtable.googleapis.com/internal/client")),
+                input -> {
+                  // filter out custom metrics and keep everything else that's registered on metric
+                  // registry
+                  String name = input.getName();
+                  return metricRegistry.getMetric(name) != null
+                      && !name.startsWith(CUSTOM_METRIC_PREFIX);
+                }),
             executor));
 
     if (enableCustomMetric) {
@@ -333,7 +340,7 @@ public static OpenTelemetrySdk createBuiltinOtel(
           PeriodicMetricReader.builder(
                   new BigtableFilteringExporter(
                       GoogleCloudMetricExporter.createWithConfiguration(metricConfig),
-                      input -> input.getName().startsWith("bigtable.custom")))
+                      input -> input.getName().startsWith(CUSTOM_METRIC_PREFIX)))
               .setInterval(Duration.ofMinutes(1))
               .build());
     }

java-bigtable/google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/internal/csm/metrics/CustomAttemptLatency.java

@@ -17,6 +17,7 @@
 
 import com.google.bigtable.v2.ClusterInformation;
 import com.google.bigtable.v2.PeerInfo;
+import com.google.cloud.bigtable.data.v2.internal.csm.MetricsImpl;
 import com.google.cloud.bigtable.data.v2.internal.csm.attributes.ClientInfo;
 import com.google.cloud.bigtable.data.v2.internal.csm.attributes.MethodInfo;
 import com.google.cloud.bigtable.data.v2.internal.csm.attributes.Util;
@@ -33,7 +34,7 @@
  * exported as a custom metric.
  */
 public class CustomAttemptLatency extends MetricWrapper<CustomSchema> {
-  private static final String NAME = "bigtable.custom.attempt_latencies";
+  private static final String NAME = MetricsImpl.CUSTOM_METRIC_PREFIX + ".attempt_latencies";
 
   public CustomAttemptLatency() {
     super(CustomSchema.INSTANCE, NAME);

java-bigtable/google-cloud-bigtable/src/test/java/com/google/cloud/bigtable/data/v2/internal/csm/MetricRegistryExportTest.java

@@ -775,6 +775,38 @@ void testPacemaker() {
                 .build());
   }
 
+  @Test
+  void testGrpcMetricExport() {
+    // 1. Record a gRPC metric using its internal name
+    // Note: gRPC metrics are usually recorded by gRPC-Java's OpenTelemetry integration,
+    // but we can simulate it by getting the instrument from the meter directly.
+    meterProvider
+        .get("grpc-java")
+        .histogramBuilder("grpc.client.attempt.duration")
+        .build()
+        .record(
+            123.0,
+            io.opentelemetry.api.common.Attributes.of(
+                io.opentelemetry.api.common.AttributeKey.stringKey("grpc.status"), "OK",
+                io.opentelemetry.api.common.AttributeKey.stringKey("grpc.method"),
+                    "Bigtable.ReadRows"));
+
+    // 2. Flush the metrics to the exporter
+    metricReader.forceFlush().join(1, TimeUnit.MINUTES);
+
+    // 3. Verify that the metric was exported under the Bigtable namespace
+    // The internal 'grpc.client.attempt.duration' should be renamed by GrpcMetric.java
+    TimeSeries timeSeries =
+        metricService.getSingleTimeSeriesByName(
+            "bigtable.googleapis.com/internal/client/grpc/client/attempt/duration");
+
+    // 4. Verify labels are correctly mapped (dots replaced with underscores)
+    assertThat(timeSeries.getMetric().getLabelsMap())
+        .containsAtLeast(
+            "grpc_status", "OK",
+            "grpc_method", "Bigtable.ReadRows");
+  }
+
   private static class FakeMetricService extends MetricServiceImplBase {
     final BlockingDeque<CreateTimeSeriesRequest> requests = new LinkedBlockingDeque<>();