census: add per call latency metric

census/src/main/java/io/grpc/census/CensusStatsModule.java

@@ -17,6 +17,7 @@
 package io.grpc.census;
 
 import static com.google.common.base.Preconditions.checkNotNull;
+import static io.grpc.census.internal.ObservabilityCensusConstants.API_LATENCY_PER_CALL;
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Stopwatch;
@@ -409,6 +410,7 @@ static final class CallAttemptsTracerFactory extends
     ClientTracer inboundMetricTracer;
     private final CensusStatsModule module;
     private final Stopwatch stopwatch;
+    private final Stopwatch callStopwatch;
     @GuardedBy("lock")
     private boolean callEnded;
     private final TagContext parentCtx;
@@ -423,6 +425,7 @@ static final class CallAttemptsTracerFactory extends
     private final Object lock = new Object();
     // write @GuardedBy("lock") and happens before read
     private long retryDelayNanos;
+    private long callLatencyNanos;
     @GuardedBy("lock")
     private int activeStreams;
     @GuardedBy("lock")
@@ -434,6 +437,7 @@ static final class CallAttemptsTracerFactory extends
       this.parentCtx = checkNotNull(parentCtx, "parentCtx");
       this.fullMethodName = checkNotNull(fullMethodName, "fullMethodName");
       this.stopwatch = module.stopwatchSupplier.get();
+      this.callStopwatch = module.stopwatchSupplier.get().start();
       TagValue methodTag = TagValue.create(fullMethodName);
       startCtx = module.tagger.toBuilder(parentCtx)
           .putLocal(RpcMeasureConstants.GRPC_CLIENT_METHOD, methodTag)
@@ -495,6 +499,7 @@ void callEnded(Status status) {
       if (!module.recordFinishedRpcs) {
         return;
       }
+      callStopwatch.stop();
       this.status = status;
       boolean shouldRecordFinishedCall = false;
       synchronized (lock) {
@@ -532,10 +537,12 @@ void recordFinishedCall() {
       if (attempts > 0) {
         retriesPerCall = attempts - 1;
       }
+      callLatencyNanos = callStopwatch.elapsed(TimeUnit.NANOSECONDS);
       MeasureMap measureMap = module.statsRecorder.newMeasureMap()
           .put(RETRIES_PER_CALL, retriesPerCall)
           .put(TRANSPARENT_RETRIES_PER_CALL, transparentRetriesPerCall.get())
-          .put(RETRY_DELAY_PER_CALL, retryDelayNanos / NANOS_PER_MILLI);
+          .put(RETRY_DELAY_PER_CALL, retryDelayNanos / NANOS_PER_MILLI)
+          .put(API_LATENCY_PER_CALL, callLatencyNanos / NANOS_PER_MILLI);
       TagValue methodTag = TagValue.create(fullMethodName);
       TagValue statusTag = TagValue.create(status.getCode().toString());
       measureMap.record(

census/src/main/java/io/grpc/census/internal/ObservabilityCensusConstants.java

@@ -25,18 +25,43 @@
 import static io.opencensus.contrib.grpc.metrics.RpcMeasureConstants.GRPC_SERVER_SENT_BYTES_PER_RPC;
 import static io.opencensus.contrib.grpc.metrics.RpcMeasureConstants.GRPC_SERVER_STATUS;
 
+import com.google.common.annotations.VisibleForTesting;
 import io.opencensus.contrib.grpc.metrics.RpcViewConstants;
 import io.opencensus.stats.Aggregation;
+import io.opencensus.stats.Measure;
+import io.opencensus.stats.Measure.MeasureDouble;
 import io.opencensus.stats.View;
 import java.util.Arrays;
 
-/** Temporary holder class for the observability specific OpenCensus constants.
- *  The class will be removed once the new views are added in OpenCensus library. */
+// TODO(dnvindhya): Remove metric and view definitions from this class once it is moved to
+// OpenCensus library.
+/**
+ * Temporary holder class for the observability specific OpenCensus constants. The class will be
+ * removed once the new views are added in OpenCensus library.
+ */
+@VisibleForTesting
 public final class ObservabilityCensusConstants {
 
   static final Aggregation AGGREGATION_WITH_BYTES_HISTOGRAM =
       RpcViewConstants.GRPC_CLIENT_SENT_BYTES_PER_RPC_VIEW.getAggregation();
 
+  static final Aggregation AGGREGATION_WITH_MILLIS_HISTOGRAM =
+      RpcViewConstants.GRPC_CLIENT_ROUNDTRIP_LATENCY_VIEW.getAggregation();
+
+  public static final MeasureDouble API_LATENCY_PER_CALL =
+      Measure.MeasureDouble.create(
+          "grpc.io/client/api_latency",
+          "Time taken by gRPC to complete an RPC from application's perspective",
+          "ms");
+
+  public static final View GRPC_CLIENT_API_LATENCY_VIEW =
+      View.create(
+          View.Name.create("grpc.io/client/api_latency"),
+          "Time taken by gRPC to complete an RPC from application's perspective",
+          API_LATENCY_PER_CALL,
+          AGGREGATION_WITH_MILLIS_HISTOGRAM,
+          Arrays.asList(GRPC_CLIENT_METHOD, GRPC_CLIENT_STATUS));
+
   public static final View GRPC_CLIENT_SENT_COMPRESSED_MESSAGE_BYTES_PER_RPC_VIEW =
       View.create(
           View.Name.create("grpc.io/client/sent_compressed_message_bytes_per_rpc"),

census/src/test/java/io/grpc/census/CensusModulesTest.java

@@ -21,6 +21,7 @@
 import static io.grpc.census.CensusStatsModule.CallAttemptsTracerFactory.RETRIES_PER_CALL;
 import static io.grpc.census.CensusStatsModule.CallAttemptsTracerFactory.RETRY_DELAY_PER_CALL;
 import static io.grpc.census.CensusStatsModule.CallAttemptsTracerFactory.TRANSPARENT_RETRIES_PER_CALL;
+import static io.grpc.census.internal.ObservabilityCensusConstants.API_LATENCY_PER_CALL;
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
@@ -63,6 +64,7 @@
 import io.grpc.Status;
 import io.grpc.census.CensusTracingModule.CallAttemptsTracerFactory;
 import io.grpc.census.internal.DeprecatedCensusConstants;
+import io.grpc.census.internal.ObservabilityCensusConstants;
 import io.grpc.internal.FakeClock;
 import io.grpc.internal.testing.StatsTestUtils;
 import io.grpc.internal.testing.StatsTestUtils.FakeStatsRecorder;
@@ -121,6 +123,8 @@
  */
 @RunWith(JUnit4.class)
 public class CensusModulesTest {
+
+  private static final double TOLERANCE = 1e-6;
   private static final CallOptions.Key<String> CUSTOM_OPTION =
       CallOptions.Key.createWithDefault("option1", "default");
   private static final CallOptions CALL_OPTIONS =
@@ -368,7 +372,7 @@ record = statsRecorder.pollRecord();
             .setSampleToLocalSpanStore(false)
             .build());
     verify(spyClientSpan, never()).end();
-    assertZeroRetryRecorded();
+    assertPerCallMetrics(0D);
   }
 
   @Test
@@ -503,7 +507,7 @@ private void subtestClientBasicStatsDefaultContext(
               DeprecatedCensusConstants.RPC_CLIENT_UNCOMPRESSED_RESPONSE_BYTES));
       assertEquals(30 + 100 + 16 + 24,
           record.getMetricAsLongOrFail(RpcMeasureConstants.GRPC_CLIENT_ROUNDTRIP_LATENCY));
-      assertZeroRetryRecorded();
+      assertPerCallMetrics(30D + 100 + 16 + 24);
     } else {
       assertNull(statsRecorder.pollRecord());
     }
@@ -691,6 +695,8 @@ record = statsRecorder.pollRecord();
     assertThat(record.getMetric(RETRIES_PER_CALL)).isEqualTo(1);
     assertThat(record.getMetric(TRANSPARENT_RETRIES_PER_CALL)).isEqualTo(2);
     assertThat(record.getMetric(RETRY_DELAY_PER_CALL)).isEqualTo(1000D + 10 + 10);
+    assertThat(record.getMetric(API_LATENCY_PER_CALL))
+        .isEqualTo(30D + 100 + 24 + 1000 + 100 + 10 + 10 + 16 + 24);
   }
 
   private void assertRealTimeMetric(
@@ -716,13 +722,14 @@ private void assertRealTimeMetric(
     assertEquals(expectedValue, record.getMetricAsLongOrFail(measure));
   }
 
-  private void assertZeroRetryRecorded() {
+  private void assertPerCallMetrics(double expectedLatencyValue) {
     StatsTestUtils.MetricsRecord record = statsRecorder.pollRecord();
     TagValue methodTag = record.tags.get(RpcMeasureConstants.GRPC_CLIENT_METHOD);
     assertEquals(method.getFullMethodName(), methodTag.asString());
     assertThat(record.getMetric(RETRIES_PER_CALL)).isEqualTo(0);
     assertThat(record.getMetric(TRANSPARENT_RETRIES_PER_CALL)).isEqualTo(0);
     assertThat(record.getMetric(RETRY_DELAY_PER_CALL)).isEqualTo(0D);
+    assertThat(record.getMetric(API_LATENCY_PER_CALL)).isEqualTo(expectedLatencyValue);
   }
 
   @Test
@@ -849,7 +856,7 @@ record = statsRecorder.pollRecord();
         3000,
         record.getMetricAsLongOrFail(RpcMeasureConstants.GRPC_CLIENT_ROUNDTRIP_LATENCY));
     assertNull(record.getMetric(RpcMeasureConstants.GRPC_CLIENT_SERVER_LATENCY));
-    assertZeroRetryRecorded();
+    assertPerCallMetrics(3000D);
   }
 
   @Test
@@ -989,7 +996,7 @@ private void subtestStatsHeadersPropagateTags(boolean propagate, boolean recordS
       assertNull(clientRecord.getMetric(DeprecatedCensusConstants.RPC_CLIENT_ERROR_COUNT));
       TagValue clientPropagatedTag = clientRecord.tags.get(StatsTestUtils.EXTRA_TAG);
       assertEquals("extra-tag-value-897", clientPropagatedTag.asString());
-      assertZeroRetryRecorded();
+      assertPerCallMetrics(0D);
     }
 
     if (!recordStats) {
@@ -1507,6 +1514,81 @@ public Long apply(AggregationData arg) {
         });
   }
 
+  @Test
+  public void callLatencyView() throws InterruptedException {
+    StatsComponent localStats = new StatsComponentImpl();
+
+    localStats
+        .getViewManager()
+        .registerView(ObservabilityCensusConstants.GRPC_CLIENT_API_LATENCY_VIEW);
+
+    CensusStatsModule localCensusStats = new CensusStatsModule(
+        tagger, tagCtxSerializer, localStats.getStatsRecorder(), fakeClock.getStopwatchSupplier(),
+        false, false, true, false /* real-time */, true);
+
+    CensusStatsModule.CallAttemptsTracerFactory callAttemptsTracerFactory =
+        new CensusStatsModule.CallAttemptsTracerFactory(
+            localCensusStats, tagger.empty(), method.getFullMethodName());
+
+    Metadata headers = new Metadata();
+    ClientStreamTracer tracer =
+        callAttemptsTracerFactory.newClientStreamTracer(STREAM_INFO, headers);
+    tracer.streamCreated(Attributes.EMPTY, headers);
+    fakeClock.forwardTime(50, MILLISECONDS);
+    Status status = Status.OK.withDescription("Success");
+    tracer.streamClosed(status);
+    callAttemptsTracerFactory.callEnded(status);
+
+    // Give OpenCensus a chance to update the views asynchronously.
+    Thread.sleep(100);
+
+    assertDistributionData(
+        localStats,
+        ObservabilityCensusConstants.GRPC_CLIENT_API_LATENCY_VIEW,
+        ImmutableList.of(TagValue.create(method.getFullMethodName()), TagValue.create("OK")),
+        50.0, 1, 0.0,
+        ImmutableList.of(
+            0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 1L,
+            0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L));
+  }
+
+  private void assertDistributionData(StatsComponent localStats, View view,
+      List<TagValue> dimension, double mean, long count, double sumOfSquaredDeviations,
+      List<Long> expectedBucketCounts) {
+    AggregationData aggregationData = localStats.getViewManager()
+        .getView(view.getName())
+        .getAggregationMap()
+        .get(dimension);
+
+    aggregationData.match(
+        Functions.</*@Nullable*/ Void>throwAssertionError(),
+        Functions.</*@Nullable*/ Void>throwAssertionError(),
+        Functions.</*@Nullable*/ Void>throwAssertionError(),
+        /* p3= */ new Function<AggregationData.DistributionData, Void>() {
+          @Override
+          public Void apply(AggregationData.DistributionData arg) {
+            assertThat(arg.getMean()).isWithin(TOLERANCE).of(mean);
+            assertThat(arg.getCount()).isEqualTo(count);
+            assertThat(arg.getSumOfSquaredDeviations())
+                .isWithin(TOLERANCE)
+                .of(sumOfSquaredDeviations);
+            assertThat(arg.getBucketCounts())
+                .containsExactlyElementsIn(expectedBucketCounts)
+                .inOrder();
+            return null;
+          }
+        },
+        Functions.</*@Nullable*/ Void>throwAssertionError(),
+        Functions.</*@Nullable*/ Void>throwAssertionError(),
+        new Function<AggregationData, Void>() {
+          @Override
+          public Void apply(AggregationData arg) {
+            assertThat(((AggregationData.DistributionData) arg).getCount()).isEqualTo(count);
+            return null;
+          }
+        });
+  }
+
   static class CallInfo<ReqT, RespT> extends ServerCallInfo<ReqT, RespT> {
     private final MethodDescriptor<ReqT, RespT> methodDescriptor;
     private final Attributes attributes;

gcp-observability/src/main/java/io/grpc/gcp/observability/GcpObservability.java

@@ -154,6 +154,7 @@ private static void registerObservabilityViews() {
     viewManager.registerView(RpcViewConstants.GRPC_CLIENT_COMPLETED_RPC_VIEW);
     viewManager.registerView(RpcViewConstants.GRPC_CLIENT_STARTED_RPC_VIEW);
     viewManager.registerView(RpcViewConstants.GRPC_CLIENT_ROUNDTRIP_LATENCY_VIEW);
+    viewManager.registerView(ObservabilityCensusConstants.GRPC_CLIENT_API_LATENCY_VIEW);
     viewManager.registerView(
         ObservabilityCensusConstants.GRPC_CLIENT_SENT_COMPRESSED_MESSAGE_BYTES_PER_RPC_VIEW);
     viewManager.registerView(