address comments

Change-Id: I21f8d0f49749722d9b22b0db949da35df7672d22

Author: mutianf

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

@@ -85,6 +85,9 @@
 import javax.annotation.concurrent.GuardedBy;
 
 public class MetricsImpl implements Metrics, Closeable {
+
+  public static final String CUSTOM_METRIC = "bigtable.internal.enable-custom-metric";
+
   private final ApiTracerFactory userTracerFactory;
   private final @Nullable OpenTelemetrySdk internalOtel;
   private final @Nullable MetricRegistry.RecorderRegistry internalRecorder;
@@ -314,11 +317,11 @@ public static OpenTelemetrySdk createBuiltinOtel(
             executor));
 
     Optional<Boolean> enableCustomMetric =
-        Optional.ofNullable(System.getenv("BIGTABLE_CUSTOM_METRIC")).map(Boolean::parseBoolean);
+        Optional.ofNullable(System.getProperty(CUSTOM_METRIC)).map(Boolean::parseBoolean);
     if (enableCustomMetric.isPresent() && enableCustomMetric.get()) {
+      // Monitored resource and project id are detected at export time
       MetricConfiguration metricConfig =
           MetricConfiguration.builder()
-              .setProjectId(clientInfo.getInstanceName().getProjectId())
               .setCredentials(credentials)
               .setInstrumentationLibraryLabelsEnabled(false)
               .build();

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;
@@ -26,6 +27,7 @@
 import io.opentelemetry.api.metrics.DoubleHistogram;
 import io.opentelemetry.api.metrics.Meter;
 import java.time.Duration;
+import java.util.Optional;
 import javax.annotation.Nullable;
 
 /**
@@ -40,13 +42,32 @@ public CustomAttemptLatency() {
   }
 
   public Recorder newRecorder(Meter meter) {
-    return new Recorder(meter);
+    Optional<Boolean> enableCustomMetric =
+        Optional.ofNullable(System.getProperty(MetricsImpl.CUSTOM_METRIC))
+            .map(Boolean::parseBoolean);
+    if (enableCustomMetric.isPresent() && enableCustomMetric.get()) {
+      return new RecorderImpl(meter);
+    } else {
+      // Skip recording high cardinality metric when it's disabled
+      return new NoopRecorder();
+    }
+  }
+
+  public abstract static class Recorder {
+    public abstract void record(
+        ClientInfo clientInfo,
+        String tableId,
+        @Nullable PeerInfo peerInfo,
+        @Nullable ClusterInformation clusterInfo,
+        MethodInfo methodInfo,
+        Status.Code code,
+        Duration latency);
   }
 
-  public static class Recorder {
+  public static class RecorderImpl extends Recorder {
     private final DoubleHistogram instrument;
 
-    private Recorder(Meter meter) {
+    private RecorderImpl(Meter meter) {
       instrument =
           meter
               .histogramBuilder(NAME)
@@ -86,4 +107,18 @@ public void record(
       instrument.record(toMillis(latency), attributes);
     }
   }
+
+  public static class NoopRecorder extends Recorder {
+    @Override
+    public void record(
+        ClientInfo clientInfo,
+        String tableId,
+        @Nullable PeerInfo peerInfo,
+        @Nullable ClusterInformation clusterInfo,
+        MethodInfo methodInfo,
+        Status.Code code,
+        Duration latency) {
+      // do nothing
+    }
+  }
 }