Add Aggregation.LastValue and AggregationData.LastValueData to support Gauge (#1055)

* Add LastValue and LastValueData

* Support LastValue and LastValueData in impl

* Use Utils instead of Precondition

* Add LastValue and remove Mean from match() method.

* Support LastValue and LastValueData in exporters and zpages.

* Update MutableLastValue, add comments on why Mean is still supported.

6 files changed, 207 insertions, 50 deletions

diff --git a/exporters/stats/prometheus/src/main/java/io/opencensus/exporter/stats/prometheus/PrometheusExportUtils.java b/exporters/stats/prometheus/src/main/java/io/opencensus/exporter/stats/prometheus/PrometheusExportUtils.java
index 14920d7b..e745b594 100644
--- a/exporters/stats/prometheus/src/main/java/io/opencensus/exporter/stats/prometheus/PrometheusExportUtils.java
+++ b/exporters/stats/prometheus/src/main/java/io/opencensus/exporter/stats/prometheus/PrometheusExportUtils.java
@@ -28,6 +28,8 @@ import io.opencensus.stats.Aggregation.Sum;
 import io.opencensus.stats.AggregationData;
 import io.opencensus.stats.AggregationData.CountData;
 import io.opencensus.stats.AggregationData.DistributionData;
+import io.opencensus.stats.AggregationData.LastValueDataDouble;
+import io.opencensus.stats.AggregationData.LastValueDataLong;
 import io.opencensus.stats.AggregationData.SumDataDouble;
 import io.opencensus.stats.AggregationData.SumDataLong;
 import io.opencensus.stats.View;
@@ -56,17 +58,19 @@ import org.checkerframework.checker.nullness.qual.Nullable;
  *
  * <p>{@link Aggregation} will be converted to a corresponding Prometheus {@link Type}. {@link Sum}
  * will be {@link Type#UNTYPED}, {@link Count} will be {@link Type#COUNTER}, {@link
- * Aggregation.Mean} will be {@link Type#SUMMARY} and {@link Distribution} will be {@link
- * Type#HISTOGRAM}. Please note we cannot set bucket boundaries for custom {@link Type#HISTOGRAM}.
+ * Aggregation.Mean} will be {@link Type#SUMMARY}, {@link Aggregation.LastValue} will be {@link
+ * Type#GAUGE} and {@link Distribution} will be {@link Type#HISTOGRAM}. Please note we cannot set
+ * bucket boundaries for custom {@link Type#HISTOGRAM}.
  *
  * <p>Each OpenCensus {@link ViewData} will be converted to a Prometheus {@link
  * MetricFamilySamples}, and each {@code Row} of the {@link ViewData} will be converted to
  * Prometheus {@link Sample}s.
  *
- * <p>{@link SumDataDouble}, {@link SumDataLong} and {@link CountData} will be converted to a single
- * {@link Sample}. {@link AggregationData.MeanData} will be converted to two {@link Sample}s sum and
- * count. {@link DistributionData} will be converted to a list of {@link Sample}s that have the sum,
- * count and histogram buckets.
+ * <p>{@link SumDataDouble}, {@link SumDataLong}, {@link LastValueDataDouble}, {@link
+ * LastValueDataLong} and {@link CountData} will be converted to a single {@link Sample}. {@link
+ * AggregationData.MeanData} will be converted to two {@link Sample}s sum and count. {@link
+ * DistributionData} will be converted to a list of {@link Sample}s that have the sum, count and
+ * histogram buckets.
  *
  * <p>{@link TagKey} and {@link TagValue} will be converted to Prometheus {@code LabelName} and
  * {@code LabelValue}. {@code Null} {@link TagValue} will be converted to an empty string.
@@ -116,9 +120,17 @@ final class PrometheusExportUtils {
     return aggregation.match(
         Functions.returnConstant(Type.UNTYPED), // SUM
         Functions.returnConstant(Type.COUNTER), // COUNT
-        Functions.returnConstant(Type.SUMMARY), // MEAN
         Functions.returnConstant(Type.HISTOGRAM), // DISTRIBUTION
-        Functions.returnConstant(Type.UNTYPED));
+        Functions.returnConstant(Type.GAUGE), // LAST VALUE
+        new Function<Aggregation, Type>() {
+          @Override
+          public Type apply(Aggregation arg) {
+            if (arg instanceof Aggregation.Mean) {
+              return Type.SUMMARY;
+            }
+            return Type.UNTYPED;
+          }
+        });
   }
 
   @VisibleForTesting
@@ -162,21 +174,6 @@ final class PrometheusExportUtils {
             return null;
           }
         },
-        new Function<AggregationData.MeanData, Void>() {
-          @Override
-          public Void apply(AggregationData.MeanData arg) {
-            samples.add(
-                new MetricFamilySamples.Sample(
-                    name + SAMPLE_SUFFIX_COUNT, labelNames, labelValues, arg.getCount()));
-            samples.add(
-                new MetricFamilySamples.Sample(
-                    name + SAMPLE_SUFFIX_SUM,
-                    labelNames,
-                    labelValues,
-                    arg.getCount() * arg.getMean()));
-            return null;
-          }
-        },
         new Function<DistributionData, Void>() {
           @Override
           public Void apply(DistributionData arg) {
@@ -197,7 +194,42 @@ final class PrometheusExportUtils {
             return null;
           }
         },
-        Functions.</*@Nullable*/ Void>throwAssertionError());
+        new Function<LastValueDataDouble, Void>() {
+          @Override
+          public Void apply(LastValueDataDouble arg) {
+            samples.add(new Sample(name, labelNames, labelValues, arg.getLastValue()));
+            return null;
+          }
+        },
+        new Function<LastValueDataLong, Void>() {
+          @Override
+          public Void apply(LastValueDataLong arg) {
+            samples.add(new Sample(name, labelNames, labelValues, arg.getLastValue()));
+            return null;
+          }
+        },
+        new Function<AggregationData, Void>() {
+          @Override
+          public Void apply(AggregationData arg) {
+            // TODO(songya): remove this once Mean aggregation is completely removed. Before that
+            // we need to continue supporting Mean, since it could still be used by users and some
+            // deprecated RPC views.
+            if (arg instanceof AggregationData.MeanData) {
+              AggregationData.MeanData meanData = (AggregationData.MeanData) arg;
+              samples.add(
+                  new MetricFamilySamples.Sample(
+                      name + SAMPLE_SUFFIX_COUNT, labelNames, labelValues, meanData.getCount()));
+              samples.add(
+                  new MetricFamilySamples.Sample(
+                      name + SAMPLE_SUFFIX_SUM,
+                      labelNames,
+                      labelValues,
+                      meanData.getCount() * meanData.getMean()));
+              return null;
+            }
+            throw new IllegalArgumentException("Unknown Aggregation.");
+          }
+        });
 
     return samples;
   }
diff --git a/exporters/stats/prometheus/src/test/java/io/opencensus/exporter/stats/prometheus/PrometheusExportUtilsTest.java b/exporters/stats/prometheus/src/test/java/io/opencensus/exporter/stats/prometheus/PrometheusExportUtilsTest.java
index 9629328d..507fd3b6 100644
--- a/exporters/stats/prometheus/src/test/java/io/opencensus/exporter/stats/prometheus/PrometheusExportUtilsTest.java
+++ b/exporters/stats/prometheus/src/test/java/io/opencensus/exporter/stats/prometheus/PrometheusExportUtilsTest.java
@@ -28,10 +28,13 @@ import io.opencensus.common.Duration;
 import io.opencensus.common.Timestamp;
 import io.opencensus.stats.Aggregation.Count;
 import io.opencensus.stats.Aggregation.Distribution;
+import io.opencensus.stats.Aggregation.LastValue;
 import io.opencensus.stats.Aggregation.Mean;
 import io.opencensus.stats.Aggregation.Sum;
 import io.opencensus.stats.AggregationData.CountData;
 import io.opencensus.stats.AggregationData.DistributionData;
+import io.opencensus.stats.AggregationData.LastValueDataDouble;
+import io.opencensus.stats.AggregationData.LastValueDataLong;
 import io.opencensus.stats.AggregationData.MeanData;
 import io.opencensus.stats.AggregationData.SumDataDouble;
 import io.opencensus.stats.AggregationData.SumDataLong;
@@ -71,6 +74,7 @@ public class PrometheusExportUtilsTest {
   private static final BucketBoundaries BUCKET_BOUNDARIES =
       BucketBoundaries.create(Arrays.asList(-5.0, 0.0, 5.0));
   private static final Distribution DISTRIBUTION = Distribution.create(BUCKET_BOUNDARIES);
+  private static final LastValue LAST_VALUE = LastValue.create();
   private static final View.Name VIEW_NAME_1 = View.Name.create("view1");
   private static final View.Name VIEW_NAME_2 = View.Name.create("view2");
   private static final View.Name VIEW_NAME_3 = View.Name.create("view-3");
@@ -90,6 +94,8 @@ public class PrometheusExportUtilsTest {
   private static final MeanData MEAN_DATA = MeanData.create(3.4, 22);
   private static final DistributionData DISTRIBUTION_DATA =
       DistributionData.create(4.4, 5, -3.2, 15.7, 135.22, Arrays.asList(0L, 2L, 2L, 1L));
+  private static final LastValueDataDouble LAST_VALUE_DATA_DOUBLE = LastValueDataDouble.create(7.9);
+  private static final LastValueDataLong LAST_VALUE_DATA_LONG = LastValueDataLong.create(66666666);
   private static final View VIEW1 =
       View.create(
           VIEW_NAME_1, DESCRIPTION, MEASURE_DOUBLE, COUNT, Arrays.asList(K1, K2), CUMULATIVE);
@@ -121,6 +127,7 @@ public class PrometheusExportUtilsTest {
     assertThat(PrometheusExportUtils.getType(DISTRIBUTION, CUMULATIVE)).isEqualTo(Type.HISTOGRAM);
     assertThat(PrometheusExportUtils.getType(SUM, CUMULATIVE)).isEqualTo(Type.UNTYPED);
     assertThat(PrometheusExportUtils.getType(MEAN, CUMULATIVE)).isEqualTo(Type.SUMMARY);
+    assertThat(PrometheusExportUtils.getType(LAST_VALUE, CUMULATIVE)).isEqualTo(Type.GAUGE);
   }
 
   @Test
@@ -190,6 +197,16 @@ public class PrometheusExportUtilsTest {
             new Sample(SAMPLE_NAME + "_count", Arrays.asList("k1"), Arrays.asList("v1"), 5),
             new Sample(SAMPLE_NAME + "_sum", Arrays.asList("k1"), Arrays.asList("v1"), 22.0))
         .inOrder();
+    assertThat(
+            PrometheusExportUtils.getSamples(
+                SAMPLE_NAME, Arrays.asList(K1, K2), Arrays.asList(V1, V2), LAST_VALUE_DATA_DOUBLE))
+        .containsExactly(
+            new Sample(SAMPLE_NAME, Arrays.asList("k1", "k2"), Arrays.asList("v1", "v2"), 7.9));
+    assertThat(
+            PrometheusExportUtils.getSamples(
+                SAMPLE_NAME, Arrays.asList(K3), Arrays.asList(V3), LAST_VALUE_DATA_LONG))
+        .containsExactly(
+            new Sample(SAMPLE_NAME, Arrays.asList("k_3"), Arrays.asList("v-3"), 66666666));
   }
 
   @Test
diff --git a/exporters/stats/signalfx/src/main/java/io/opencensus/exporter/stats/signalfx/SignalFxSessionAdaptor.java b/exporters/stats/signalfx/src/main/java/io/opencensus/exporter/stats/signalfx/SignalFxSessionAdaptor.java
index fb0db8a7..2eb75c4c 100644
--- a/exporters/stats/signalfx/src/main/java/io/opencensus/exporter/stats/signalfx/SignalFxSessionAdaptor.java
+++ b/exporters/stats/signalfx/src/main/java/io/opencensus/exporter/stats/signalfx/SignalFxSessionAdaptor.java
@@ -24,11 +24,12 @@ import com.signalfx.metrics.protobuf.SignalFxProtocolBuffers.Datum;
 import com.signalfx.metrics.protobuf.SignalFxProtocolBuffers.Dimension;
 import com.signalfx.metrics.protobuf.SignalFxProtocolBuffers.MetricType;
 import io.opencensus.common.Function;
-import io.opencensus.common.Functions;
 import io.opencensus.stats.Aggregation;
 import io.opencensus.stats.AggregationData;
 import io.opencensus.stats.AggregationData.CountData;
 import io.opencensus.stats.AggregationData.DistributionData;
+import io.opencensus.stats.AggregationData.LastValueDataDouble;
+import io.opencensus.stats.AggregationData.LastValueDataLong;
 import io.opencensus.stats.AggregationData.SumDataDouble;
 import io.opencensus.stats.AggregationData.SumDataLong;
 import io.opencensus.stats.View;
@@ -88,7 +89,7 @@ final class SignalFxSessionAdaptor {
   @javax.annotation.Nullable
   static MetricType getMetricTypeForAggregation(
       Aggregation aggregation, View.AggregationWindow window) {
-    if (aggregation instanceof Aggregation.Mean) {
+    if (aggregation instanceof Aggregation.Mean || aggregation instanceof Aggregation.LastValue) {
       return MetricType.GAUGE;
     } else if (aggregation instanceof Aggregation.Count || aggregation instanceof Aggregation.Sum) {
       if (window instanceof View.AggregationWindow.Cumulative) {
@@ -148,13 +149,6 @@ final class SignalFxSessionAdaptor {
             return null;
           }
         },
-        new Function<AggregationData.MeanData, Void>() {
-          @Override
-          public Void apply(AggregationData.MeanData arg) {
-            builder.setDoubleValue(arg.getMean());
-            return null;
-          }
-        },
         new Function<DistributionData, Void>() {
           @Override
           public Void apply(DistributionData arg) {
@@ -162,7 +156,33 @@ final class SignalFxSessionAdaptor {
             throw new IllegalArgumentException("Distribution aggregations are not supported");
           }
         },
-        Functions.</*@Nullable*/ Void>throwIllegalArgumentException());
+        new Function<LastValueDataDouble, Void>() {
+          @Override
+          public Void apply(LastValueDataDouble arg) {
+            builder.setDoubleValue(arg.getLastValue());
+            return null;
+          }
+        },
+        new Function<LastValueDataLong, Void>() {
+          @Override
+          public Void apply(LastValueDataLong arg) {
+            builder.setIntValue(arg.getLastValue());
+            return null;
+          }
+        },
+        new Function<AggregationData, Void>() {
+          @Override
+          public Void apply(AggregationData arg) {
+            // TODO(songya): remove this once Mean aggregation is completely removed. Before that
+            // we need to continue supporting Mean, since it could still be used by users and some
+            // deprecated RPC views.
+            if (arg instanceof AggregationData.MeanData) {
+              builder.setDoubleValue(((AggregationData.MeanData) arg).getMean());
+              return null;
+            }
+            throw new IllegalArgumentException("Unknown Aggregation.");
+          }
+        });
     return builder.build();
   }
 }
diff --git a/exporters/stats/signalfx/src/test/java/io/opencensus/exporter/stats/signalfx/SignalFxSessionAdaptorTest.java b/exporters/stats/signalfx/src/test/java/io/opencensus/exporter/stats/signalfx/SignalFxSessionAdaptorTest.java
index 3ce2e869..34f4dfa7 100644
--- a/exporters/stats/signalfx/src/test/java/io/opencensus/exporter/stats/signalfx/SignalFxSessionAdaptorTest.java
+++ b/exporters/stats/signalfx/src/test/java/io/opencensus/exporter/stats/signalfx/SignalFxSessionAdaptorTest.java
@@ -34,6 +34,8 @@ import io.opencensus.stats.Aggregation;
 import io.opencensus.stats.AggregationData;
 import io.opencensus.stats.AggregationData.CountData;
 import io.opencensus.stats.AggregationData.DistributionData;
+import io.opencensus.stats.AggregationData.LastValueDataDouble;
+import io.opencensus.stats.AggregationData.LastValueDataLong;
 import io.opencensus.stats.AggregationData.MeanData;
 import io.opencensus.stats.AggregationData.SumDataDouble;
 import io.opencensus.stats.AggregationData.SumDataLong;
@@ -108,6 +110,14 @@ public class SignalFxSessionAdaptorTest {
         SignalFxSessionAdaptor.getMetricTypeForAggregation(
             Aggregation.Distribution.create(BucketBoundaries.create(ImmutableList.of(3.15d))),
             AggregationWindow.Cumulative.create()));
+    assertEquals(
+        MetricType.GAUGE,
+        SignalFxSessionAdaptor.getMetricTypeForAggregation(
+            Aggregation.LastValue.create(), AggregationWindow.Cumulative.create()));
+    assertEquals(
+        MetricType.GAUGE,
+        SignalFxSessionAdaptor.getMetricTypeForAggregation(
+            Aggregation.LastValue.create(), AggregationWindow.Interval.create(ONE_SECOND)));
   }
 
   @Test
@@ -206,6 +216,26 @@ public class SignalFxSessionAdaptorTest {
   }
 
   @Test
+  public void createDatumFromLastValueDouble() {
+    LastValueDataDouble data = LastValueDataDouble.create(12.2);
+    Datum datum = SignalFxSessionAdaptor.createDatum(data);
+    assertTrue(datum.hasDoubleValue());
+    assertFalse(datum.hasIntValue());
+    assertFalse(datum.hasStrValue());
+    assertEquals(12.2, datum.getDoubleValue(), 0d);
+  }
+
+  @Test
+  public void createDatumFromLastValueLong() {
+    LastValueDataLong data = LastValueDataLong.create(100000);
+    Datum datum = SignalFxSessionAdaptor.createDatum(data);
+    assertFalse(datum.hasDoubleValue());
+    assertTrue(datum.hasIntValue());
+    assertFalse(datum.hasStrValue());
+    assertEquals(100000, datum.getIntValue());
+  }
+
+  @Test
   public void adaptViewIntoDatapoints() {
     Map<List<TagValue>, AggregationData> map =
         ImmutableMap.<List<TagValue>, AggregationData>of(
diff --git a/exporters/stats/stackdriver/src/main/java/io/opencensus/exporter/stats/stackdriver/StackdriverExportUtils.java b/exporters/stats/stackdriver/src/main/java/io/opencensus/exporter/stats/stackdriver/StackdriverExportUtils.java
index 8dc5f76c..642d39bc 100644
--- a/exporters/stats/stackdriver/src/main/java/io/opencensus/exporter/stats/stackdriver/StackdriverExportUtils.java
+++ b/exporters/stats/stackdriver/src/main/java/io/opencensus/exporter/stats/stackdriver/StackdriverExportUtils.java
@@ -44,9 +44,12 @@ import io.opencensus.contrib.monitoredresource.util.MonitoredResource.GcpGkeCont
 import io.opencensus.contrib.monitoredresource.util.MonitoredResourceUtils;
 import io.opencensus.contrib.monitoredresource.util.ResourceType;
 import io.opencensus.stats.Aggregation;
+import io.opencensus.stats.Aggregation.LastValue;
 import io.opencensus.stats.AggregationData;
 import io.opencensus.stats.AggregationData.CountData;
 import io.opencensus.stats.AggregationData.DistributionData;
+import io.opencensus.stats.AggregationData.LastValueDataDouble;
+import io.opencensus.stats.AggregationData.LastValueDataLong;
 import io.opencensus.stats.AggregationData.SumDataDouble;
 import io.opencensus.stats.AggregationData.SumDataLong;
 import io.opencensus.stats.BucketBoundaries;
@@ -131,7 +134,7 @@ final class StackdriverExportUtils {
             .setValueType(ValueType.STRING)
             .build());
     builder.setUnit(createUnit(view.getAggregation(), view.getMeasure()));
-    builder.setMetricKind(createMetricKind(view.getWindow()));
+    builder.setMetricKind(createMetricKind(view.getWindow(), view.getAggregation()));
     builder.setValueType(createValueType(view.getAggregation(), view.getMeasure()));
     return builder.build();
   }
@@ -153,7 +156,10 @@ final class StackdriverExportUtils {
 
   // Construct a MetricKind from an AggregationWindow
   @VisibleForTesting
-  static MetricKind createMetricKind(View.AggregationWindow window) {
+  static MetricKind createMetricKind(View.AggregationWindow window, Aggregation aggregation) {
+    if (aggregation instanceof LastValue) {
+      return MetricKind.GAUGE;
+    }
     return window.match(
         Functions.returnConstant(MetricKind.CUMULATIVE), // Cumulative
         // TODO(songya): We don't support exporting Interval stats to StackDriver in this version.
@@ -167,8 +173,8 @@ final class StackdriverExportUtils {
     return aggregation.match(
         Functions.returnConstant(measure.getUnit()),
         Functions.returnConstant("1"), // Count
-        Functions.returnConstant(measure.getUnit()), // Mean
         Functions.returnConstant(measure.getUnit()), // Distribution
+        Functions.returnConstant(measure.getUnit()), // LastValue
         Functions.returnConstant(measure.getUnit()));
   }
 
@@ -183,9 +189,24 @@ final class StackdriverExportUtils {
                 Functions.returnConstant(MetricDescriptor.ValueType.INT64), // Sum Long
                 Functions.returnConstant(MetricDescriptor.ValueType.UNRECOGNIZED))),
         Functions.returnConstant(MetricDescriptor.ValueType.INT64), // Count
-        Functions.returnConstant(MetricDescriptor.ValueType.DOUBLE), // Mean
         Functions.returnConstant(MetricDescriptor.ValueType.DISTRIBUTION), // Distribution
-        Functions.returnConstant(MetricDescriptor.ValueType.UNRECOGNIZED));
+        Functions.returnConstant(
+            measure.match(
+                Functions.returnConstant(MetricDescriptor.ValueType.DOUBLE), // LastValue Double
+                Functions.returnConstant(MetricDescriptor.ValueType.INT64), // LastValue Long
+                Functions.returnConstant(MetricDescriptor.ValueType.UNRECOGNIZED))),
+        new Function<Aggregation, MetricDescriptor.ValueType>() {
+          @Override
+          public MetricDescriptor.ValueType apply(Aggregation arg) {
+            // TODO(songya): remove this once Mean aggregation is completely removed. Before that
+            // we need to continue supporting Mean, since it could still be used by users and some
+            // deprecated RPC views.
+            if (arg instanceof Aggregation.Mean) {
+              return MetricDescriptor.ValueType.DOUBLE;
+            }
+            return MetricDescriptor.ValueType.UNRECOGNIZED;
+          }
+        });
   }
 
   // Convert ViewData to a list of TimeSeries, so that ViewData can be uploaded to Stackdriver.
@@ -203,7 +224,7 @@ final class StackdriverExportUtils {
 
     // Shared fields for all TimeSeries generated from the same ViewData
     TimeSeries.Builder shared = TimeSeries.newBuilder();
-    shared.setMetricKind(createMetricKind(view.getWindow()));
+    shared.setMetricKind(createMetricKind(view.getWindow(), view.getAggregation()));
     shared.setResource(monitoredResource);
     shared.setValueType(createValueType(view.getAggregation(), view.getMeasure()));
 
@@ -301,13 +322,6 @@ final class StackdriverExportUtils {
             return null;
           }
         },
-        new Function<AggregationData.MeanData, Void>() {
-          @Override
-          public Void apply(AggregationData.MeanData arg) {
-            builder.setDoubleValue(arg.getMean());
-            return null;
-          }
-        },
         new Function<DistributionData, Void>() {
           @Override
           public Void apply(DistributionData arg) {
@@ -320,7 +334,33 @@ final class StackdriverExportUtils {
             return null;
           }
         },
-        Functions.</*@Nullable*/ Void>throwIllegalArgumentException());
+        new Function<LastValueDataDouble, Void>() {
+          @Override
+          public Void apply(LastValueDataDouble arg) {
+            builder.setDoubleValue(arg.getLastValue());
+            return null;
+          }
+        },
+        new Function<LastValueDataLong, Void>() {
+          @Override
+          public Void apply(LastValueDataLong arg) {
+            builder.setInt64Value(arg.getLastValue());
+            return null;
+          }
+        },
+        new Function<AggregationData, Void>() {
+          @Override
+          public Void apply(AggregationData arg) {
+            // TODO(songya): remove this once Mean aggregation is completely removed. Before that
+            // we need to continue supporting Mean, since it could still be used by users and some
+            // deprecated RPC views.
+            if (arg instanceof AggregationData.MeanData) {
+              builder.setDoubleValue(((AggregationData.MeanData) arg).getMean());
+              return null;
+            }
+            throw new IllegalArgumentException("Unknown Aggregation");
+          }
+        });
     return builder.build();
   }
 
diff --git a/exporters/stats/stackdriver/src/test/java/io/opencensus/exporter/stats/stackdriver/StackdriverExportUtilsTest.java b/exporters/stats/stackdriver/src/test/java/io/opencensus/exporter/stats/stackdriver/StackdriverExportUtilsTest.java
index a78a96ea..7b808c79 100644
--- a/exporters/stats/stackdriver/src/test/java/io/opencensus/exporter/stats/stackdriver/StackdriverExportUtilsTest.java
+++ b/exporters/stats/stackdriver/src/test/java/io/opencensus/exporter/stats/stackdriver/StackdriverExportUtilsTest.java
@@ -35,10 +35,13 @@ import io.opencensus.common.Duration;
 import io.opencensus.common.Timestamp;
 import io.opencensus.stats.Aggregation.Count;
 import io.opencensus.stats.Aggregation.Distribution;
+import io.opencensus.stats.Aggregation.LastValue;
 import io.opencensus.stats.Aggregation.Mean;
 import io.opencensus.stats.Aggregation.Sum;
 import io.opencensus.stats.AggregationData.CountData;
 import io.opencensus.stats.AggregationData.DistributionData;
+import io.opencensus.stats.AggregationData.LastValueDataDouble;
+import io.opencensus.stats.AggregationData.LastValueDataLong;
 import io.opencensus.stats.AggregationData.MeanData;
 import io.opencensus.stats.AggregationData.SumDataDouble;
 import io.opencensus.stats.AggregationData.SumDataLong;
@@ -92,6 +95,7 @@ public class StackdriverExportUtilsTest {
   private static final Count COUNT = Count.create();
   private static final Mean MEAN = Mean.create();
   private static final Distribution DISTRIBUTION = Distribution.create(BUCKET_BOUNDARIES);
+  private static final LastValue LAST_VALUE = LastValue.create();
   private static final String PROJECT_ID = "id";
   private static final MonitoredResource DEFAULT_RESOURCE =
       MonitoredResource.newBuilder().setType("global").build();
@@ -116,10 +120,14 @@ public class StackdriverExportUtilsTest {
 
   @Test
   public void createMetricKind() {
-    assertThat(StackdriverExportUtils.createMetricKind(CUMULATIVE))
+    assertThat(StackdriverExportUtils.createMetricKind(CUMULATIVE, SUM))
         .isEqualTo(MetricKind.CUMULATIVE);
-    assertThat(StackdriverExportUtils.createMetricKind(INTERVAL))
+    assertThat(StackdriverExportUtils.createMetricKind(INTERVAL, COUNT))
         .isEqualTo(MetricKind.UNRECOGNIZED);
+    assertThat(StackdriverExportUtils.createMetricKind(CUMULATIVE, LAST_VALUE))
+        .isEqualTo(MetricKind.GAUGE);
+    assertThat(StackdriverExportUtils.createMetricKind(INTERVAL, LAST_VALUE))
+        .isEqualTo(MetricKind.GAUGE);
   }
 
   @Test
@@ -140,6 +148,10 @@ public class StackdriverExportUtilsTest {
         .isEqualTo(MetricDescriptor.ValueType.DISTRIBUTION);
     assertThat(StackdriverExportUtils.createValueType(DISTRIBUTION, MEASURE_LONG))
         .isEqualTo(MetricDescriptor.ValueType.DISTRIBUTION);
+    assertThat(StackdriverExportUtils.createValueType(LAST_VALUE, MEASURE_DOUBLE))
+        .isEqualTo(MetricDescriptor.ValueType.DOUBLE);
+    assertThat(StackdriverExportUtils.createValueType(LAST_VALUE, MEASURE_LONG))
+        .isEqualTo(MetricDescriptor.ValueType.INT64);
   }
 
   @Test
@@ -149,6 +161,8 @@ public class StackdriverExportUtilsTest {
     assertThat(StackdriverExportUtils.createUnit(MEAN, MEASURE_DOUBLE)).isEqualTo(MEASURE_UNIT);
     assertThat(StackdriverExportUtils.createUnit(DISTRIBUTION, MEASURE_DOUBLE))
         .isEqualTo(MEASURE_UNIT);
+    assertThat(StackdriverExportUtils.createUnit(LAST_VALUE, MEASURE_DOUBLE))
+        .isEqualTo(MEASURE_UNIT);
   }
 
   @Test
@@ -288,6 +302,10 @@ public class StackdriverExportUtilsTest {
                 .setDistributionValue(
                     StackdriverExportUtils.createDistribution(distributionData, BUCKET_BOUNDARIES))
                 .build());
+    assertThat(StackdriverExportUtils.createTypedValue(LAST_VALUE, LastValueDataDouble.create(9.9)))
+        .isEqualTo(TypedValue.newBuilder().setDoubleValue(9.9).build());
+    assertThat(StackdriverExportUtils.createTypedValue(LAST_VALUE, LastValueDataLong.create(90000)))
+        .isEqualTo(TypedValue.newBuilder().setInt64Value(90000).build());
   }
 
   @Test