Metrics: Combine TimeSeriesCumulative and TimeSeriesGauge. (#1380)

13 files changed, 185 insertions, 661 deletions

diff --git a/api/src/main/java/io/opencensus/metrics/Metric.java b/api/src/main/java/io/opencensus/metrics/Metric.java
index e8be0b90..9cbd418b 100644
--- a/api/src/main/java/io/opencensus/metrics/Metric.java
+++ b/api/src/main/java/io/opencensus/metrics/Metric.java
@@ -19,8 +19,10 @@ package io.opencensus.metrics;
 import com.google.auto.value.AutoValue;
 import io.opencensus.common.ExperimentalApi;
 import io.opencensus.internal.Utils;
-import io.opencensus.metrics.TimeSeriesList.TimeSeriesCumulativeList;
-import io.opencensus.metrics.TimeSeriesList.TimeSeriesGaugeList;
+import io.opencensus.metrics.Value.ValueDistribution;
+import io.opencensus.metrics.Value.ValueDouble;
+import io.opencensus.metrics.Value.ValueLong;
+import java.util.List;
 import javax.annotation.concurrent.Immutable;
 
 /**
@@ -39,11 +41,11 @@ public abstract class Metric {
    * Creates a {@link Metric}.
    *
    * @param metricDescriptor the {@link MetricDescriptor}.
-   * @param timeSeriesList the {@link TimeSeriesList} for this metric.
+   * @param timeSeriesList the {@link TimeSeries} list for this metric.
    * @return a {@code Metric}.
    * @since 0.16
    */
-  public static Metric create(MetricDescriptor metricDescriptor, TimeSeriesList timeSeriesList) {
+  public static Metric create(MetricDescriptor metricDescriptor, List<TimeSeries> timeSeriesList) {
     checkTypeMatch(metricDescriptor.getType(), timeSeriesList);
     return new AutoValue_Metric(metricDescriptor, timeSeriesList);
   }
@@ -57,32 +59,43 @@ public abstract class Metric {
   public abstract MetricDescriptor getMetricDescriptor();
 
   /**
-   * Returns the {@link TimeSeriesList} for this metric.
+   * Returns the {@link TimeSeries} list for this metric.
    *
-   * <p>The type of the {@link TimeSeriesList} must match {@link MetricDescriptor.Type}.
+   * <p>The type of the {@link TimeSeries#getPoints()} must match {@link MetricDescriptor.Type}.
    *
    * @return the {@code TimeSeriesList} for this metric.
    * @since 0.16
    */
-  public abstract TimeSeriesList getTimeSeriesList();
+  public abstract List<TimeSeries> getTimeSeriesList();
 
-  private static void checkTypeMatch(MetricDescriptor.Type type, TimeSeriesList timeSeriesList) {
-    switch (type) {
-      case GAUGE_INT64:
-      case GAUGE_DOUBLE:
-        Utils.checkArgument(
-            timeSeriesList instanceof TimeSeriesGaugeList,
-            String.format(
-                "Type mismatch: %s, %s.", type, timeSeriesList.getClass().getSimpleName()));
-        break;
-      case CUMULATIVE_DISTRIBUTION:
-      case CUMULATIVE_DOUBLE:
-      case CUMULATIVE_INT64:
-        Utils.checkArgument(
-            timeSeriesList instanceof TimeSeriesCumulativeList,
-            String.format(
-                "Type mismatch: %s, %s.", type, timeSeriesList.getClass().getSimpleName()));
-        break;
+  private static void checkTypeMatch(MetricDescriptor.Type type, List<TimeSeries> timeSeriesList) {
+    for (TimeSeries timeSeries : timeSeriesList) {
+      for (Point point : timeSeries.getPoints()) {
+        Value value = point.getValue();
+        String valueClassName = "";
+        if (value.getClass().getSuperclass() != null) { // work around nullness check
+          // AutoValue classes should always have a super class.
+          valueClassName = value.getClass().getSuperclass().getSimpleName();
+        }
+        switch (type) {
+          case GAUGE_INT64:
+          case CUMULATIVE_INT64:
+            Utils.checkArgument(
+                value instanceof ValueLong,
+                String.format("Type mismatch: %s, %s.", type, valueClassName));
+            break;
+          case CUMULATIVE_DOUBLE:
+          case GAUGE_DOUBLE:
+            Utils.checkArgument(
+                value instanceof ValueDouble,
+                String.format("Type mismatch: %s, %s.", type, valueClassName));
+            break;
+          case CUMULATIVE_DISTRIBUTION:
+            Utils.checkArgument(
+                value instanceof ValueDistribution,
+                String.format("Type mismatch: %s, %s.", type, valueClassName));
+        }
+      }
     }
   }
 }
diff --git a/api/src/main/java/io/opencensus/metrics/TimeSeries.java b/api/src/main/java/io/opencensus/metrics/TimeSeries.java
index bbbfe0e4..c62b6b72 100644
--- a/api/src/main/java/io/opencensus/metrics/TimeSeries.java
+++ b/api/src/main/java/io/opencensus/metrics/TimeSeries.java
@@ -16,16 +16,52 @@
 
 package io.opencensus.metrics;
 
+import com.google.auto.value.AutoValue;
+import io.opencensus.common.ExperimentalApi;
+import io.opencensus.common.Timestamp;
+import io.opencensus.internal.Utils;
+import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
+import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
 
-/** A collection of data points that describes the time-varying values of a {@code Metric}. */
+/**
+ * A collection of data points that describes the time-varying values of a {@code Metric}.
+ *
+ * @since 0.16
+ */
+@ExperimentalApi
 @Immutable
-abstract class TimeSeries {
+@AutoValue
+public abstract class TimeSeries {
 
   TimeSeries() {}
 
   /**
+   * Creates a {@link TimeSeries}.
+   *
+   * @param labelValues the {@code LabelValue}s that uniquely identify this {@code TimeSeries}.
+   * @param points the data {@code Point}s of this {@code TimeSeries}.
+   * @param startTimestamp the start {@code Timestamp} of this {@code TimeSeries}. Must be non-null
+   *     for cumulative {@code Point}s.
+   * @return a {@code TimeSeries}.
+   * @since 0.16
+   */
+  public static TimeSeries create(
+      List<LabelValue> labelValues, List<Point> points, @Nullable Timestamp startTimestamp) {
+    // Fail fast on null lists to prevent NullPointerException when copying the lists.
+    Utils.checkNotNull(labelValues, "labelValues");
+    Utils.checkNotNull(points, "points");
+    Utils.checkListElementNotNull(labelValues, "labelValue");
+    Utils.checkListElementNotNull(points, "point");
+    return new AutoValue_TimeSeries(
+        Collections.unmodifiableList(new ArrayList<LabelValue>(labelValues)),
+        Collections.unmodifiableList(new ArrayList<Point>(points)),
+        startTimestamp);
+  }
+
+  /**
    * Returns the set of {@link LabelValue}s that uniquely identify this {@link TimeSeries}.
    *
    * <p>Apply to all {@link Point}s.
@@ -45,4 +81,14 @@ abstract class TimeSeries {
    * @since 0.16
    */
   public abstract List<Point> getPoints();
+
+  /**
+   * Returns the start {@link Timestamp} of this {@link TimeSeries} if the {@link Point}s are
+   * cumulative, or {@code null} if the {@link Point}s are gauge.
+   *
+   * @return the start {@code Timestamp} or {@code null}.
+   * @since 0.16
+   */
+  @Nullable
+  public abstract Timestamp getStartTimestamp();
 }
diff --git a/api/src/main/java/io/opencensus/metrics/TimeSeriesCumulative.java b/api/src/main/java/io/opencensus/metrics/TimeSeriesCumulative.java
deleted file mode 100644
index 5f48b770..00000000
--- a/api/src/main/java/io/opencensus/metrics/TimeSeriesCumulative.java
+++ /dev/null
@@ -1,70 +0,0 @@
-/*
- * Copyright 2018, OpenCensus Authors
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package io.opencensus.metrics;
-
-import com.google.auto.value.AutoValue;
-import io.opencensus.common.ExperimentalApi;
-import io.opencensus.common.Timestamp;
-import io.opencensus.internal.Utils;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.List;
-import javax.annotation.concurrent.Immutable;
-
-/**
- * A collection of data points that describes the time-varying values of a cumulative {@code
- * Metric}.
- *
- * @since 0.16
- */
-@ExperimentalApi
-@Immutable
-@AutoValue
-public abstract class TimeSeriesCumulative extends TimeSeries {
-
-  TimeSeriesCumulative() {}
-
-  /**
-   * Creates a {@link TimeSeriesCumulative}.
-   *
-   * @param labelValues the {@code LabelValue}s that uniquely identify this {@code TimeSeries}.
-   * @param points the data {@code Point}s of this {@code TimeSeries}.
-   * @param startTimestamp the start {@code Timestamp} of this {@code TimeSeriesCumulative}.
-   * @return a {@code TimeSeriesCumulative}.
-   * @since 0.16
-   */
-  public static TimeSeriesCumulative create(
-      List<LabelValue> labelValues, List<Point> points, Timestamp startTimestamp) {
-    // Fail fast on null lists to prevent NullPointerException when copying the lists.
-    Utils.checkNotNull(labelValues, "labelValues");
-    Utils.checkNotNull(points, "points");
-    Utils.checkListElementNotNull(labelValues, "labelValue");
-    Utils.checkListElementNotNull(points, "point");
-    return new AutoValue_TimeSeriesCumulative(
-        Collections.unmodifiableList(new ArrayList<LabelValue>(labelValues)),
-        Collections.unmodifiableList(new ArrayList<Point>(points)),
-        startTimestamp);
-  }
-
-  /**
-   * Returns the start {@link Timestamp} of this {@link TimeSeriesCumulative}.
-   *
-   * @return the start {@code Timestamp}.
-   * @since 0.16
-   */
-  public abstract Timestamp getStartTimestamp();
-}
diff --git a/api/src/main/java/io/opencensus/metrics/TimeSeriesGauge.java b/api/src/main/java/io/opencensus/metrics/TimeSeriesGauge.java
deleted file mode 100644
index 717505a4..00000000
--- a/api/src/main/java/io/opencensus/metrics/TimeSeriesGauge.java
+++ /dev/null
@@ -1,57 +0,0 @@
-/*
- * Copyright 2018, OpenCensus Authors
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package io.opencensus.metrics;
-
-import com.google.auto.value.AutoValue;
-import io.opencensus.common.ExperimentalApi;
-import io.opencensus.internal.Utils;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.List;
-import javax.annotation.concurrent.Immutable;
-
-/**
- * A collection of data points that describes the time-varying values of a gauge {@code Metric}.
- *
- * @since 0.16
- */
-@ExperimentalApi
-@Immutable
-@AutoValue
-public abstract class TimeSeriesGauge extends TimeSeries {
-
-  TimeSeriesGauge() {}
-
-  /**
-   * Creates a {@link TimeSeriesGauge}.
-   *
-   * @param labelValues the {@code LabelValue}s that uniquely identify this {@code TimeSeries}.
-   * @param points the data {@code Point}s of this {@code TimeSeries}.
-   * @return a {@code TimeSeriesGauge}.
-   * @since 0.16
-   */
-  public static TimeSeriesGauge create(List<LabelValue> labelValues, List<Point> points) {
-    // Fail fast on null lists to prevent NullPointerException when copying the lists.
-    Utils.checkNotNull(labelValues, "labelValues");
-    Utils.checkNotNull(points, "points");
-    Utils.checkListElementNotNull(labelValues, "labelValue");
-    Utils.checkListElementNotNull(points, "point");
-    return new AutoValue_TimeSeriesGauge(
-        Collections.unmodifiableList(new ArrayList<LabelValue>(labelValues)),
-        Collections.unmodifiableList(new ArrayList<Point>(points)));
-  }
-}
diff --git a/api/src/main/java/io/opencensus/metrics/TimeSeriesList.java b/api/src/main/java/io/opencensus/metrics/TimeSeriesList.java
deleted file mode 100644
index 6138eac2..00000000
--- a/api/src/main/java/io/opencensus/metrics/TimeSeriesList.java
+++ /dev/null
@@ -1,134 +0,0 @@
-/*
- * Copyright 2018, OpenCensus Authors
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package io.opencensus.metrics;
-
-import com.google.auto.value.AutoValue;
-import io.opencensus.common.ExperimentalApi;
-import io.opencensus.common.Function;
-import io.opencensus.internal.Utils;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.List;
-import javax.annotation.concurrent.Immutable;
-
-/**
- * Class that holds a list of either {@link TimeSeriesGauge} or {@link TimeSeriesCumulative}.
- *
- * @since 0.16
- */
-@ExperimentalApi
-@Immutable
-public abstract class TimeSeriesList {
-
-  TimeSeriesList() {}
-
-  /**
-   * Applies the given match function to the underlying data type.
-   *
-   * @since 0.16
-   */
-  public abstract <T> T match(
-      Function<? super TimeSeriesGaugeList, T> gaugeListFunction,
-      Function<? super TimeSeriesCumulativeList, T> cumulativeListFunction,
-      Function<? super TimeSeriesList, T> defaultFunction);
-
-  /**
-   * Class that holds a list of {@link TimeSeriesGauge}.
-   *
-   * @since 0.16
-   */
-  @ExperimentalApi
-  @Immutable
-  @AutoValue
-  public abstract static class TimeSeriesGaugeList extends TimeSeriesList {
-
-    TimeSeriesGaugeList() {}
-
-    @Override
-    public final <T> T match(
-        Function<? super TimeSeriesGaugeList, T> gaugeListFunction,
-        Function<? super TimeSeriesCumulativeList, T> cumulativeListFunction,
-        Function<? super TimeSeriesList, T> defaultFunction) {
-      return gaugeListFunction.apply(this);
-    }
-
-    /**
-     * Creates a {@link TimeSeriesGaugeList}.
-     *
-     * @param list a list of {@link TimeSeriesGauge}.
-     * @return a {code TimeSeriesGaugeList}.
-     * @since 0.16
-     */
-    public static TimeSeriesGaugeList create(List<TimeSeriesGauge> list) {
-      Utils.checkNotNull(list, "list");
-      Utils.checkListElementNotNull(list, "timeSeriesGauge");
-      return new AutoValue_TimeSeriesList_TimeSeriesGaugeList(
-          Collections.unmodifiableList(new ArrayList<TimeSeriesGauge>(list)));
-    }
-
-    /**
-     * Returns the list of {@link TimeSeriesGauge}.
-     *
-     * @return the list of {@code TimeSeriesGauge}.
-     * @since 0.16
-     */
-    public abstract List<TimeSeriesGauge> getList();
-  }
-
-  /**
-   * Class that holds a list of {@link TimeSeriesCumulative}.
-   *
-   * @since 0.16
-   */
-  @ExperimentalApi
-  @Immutable
-  @AutoValue
-  public abstract static class TimeSeriesCumulativeList extends TimeSeriesList {
-
-    TimeSeriesCumulativeList() {}
-
-    @Override
-    public final <T> T match(
-        Function<? super TimeSeriesGaugeList, T> gaugeListFunction,
-        Function<? super TimeSeriesCumulativeList, T> cumulativeListFunction,
-        Function<? super TimeSeriesList, T> defaultFunction) {
-      return cumulativeListFunction.apply(this);
-    }
-
-    /**
-     * Creates a {@link TimeSeriesCumulativeList}.
-     *
-     * @param list a list of {@link TimeSeriesCumulative}.
-     * @return a {code TimeSeriesCumulativeList}.
-     * @since 0.16
-     */
-    public static TimeSeriesCumulativeList create(List<TimeSeriesCumulative> list) {
-      Utils.checkNotNull(list, "list");
-      Utils.checkListElementNotNull(list, "timeSeriesCumulative");
-      return new AutoValue_TimeSeriesList_TimeSeriesCumulativeList(
-          Collections.unmodifiableList(new ArrayList<TimeSeriesCumulative>(list)));
-    }
-
-    /**
-     * Returns the list of {@link TimeSeriesCumulative}.
-     *
-     * @return the list of {@code TimeSeriesCumulative}.
-     * @since 0.16
-     */
-    public abstract List<TimeSeriesCumulative> getList();
-  }
-}
diff --git a/api/src/test/java/io/opencensus/metrics/MetricTest.java b/api/src/test/java/io/opencensus/metrics/MetricTest.java
index 59838ef4..37deed4b 100644
--- a/api/src/test/java/io/opencensus/metrics/MetricTest.java
+++ b/api/src/test/java/io/opencensus/metrics/MetricTest.java
@@ -21,10 +21,9 @@ import static com.google.common.truth.Truth.assertThat;
 import com.google.common.testing.EqualsTester;
 import io.opencensus.common.Timestamp;
 import io.opencensus.metrics.MetricDescriptor.Type;
-import io.opencensus.metrics.TimeSeriesList.TimeSeriesCumulativeList;
-import io.opencensus.metrics.TimeSeriesList.TimeSeriesGaugeList;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.List;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
@@ -61,47 +60,41 @@ public class MetricTest {
   private static final Point POINT_1 = Point.create(VALUE_DOUBLE_1, TIMESTAMP_2);
   private static final Point POINT_2 = Point.create(VALUE_DOUBLE_2, TIMESTAMP_3);
   private static final Point POINT_3 = Point.create(VALUE_LONG, TIMESTAMP_3);
-  private static final TimeSeriesGauge GAUGE_TIME_SERIES_1 =
-      TimeSeriesGauge.create(Arrays.asList(LABEL_VALUE_1, LABEL_VALUE_2), Arrays.asList(POINT_1));
-  private static final TimeSeriesGauge GAUGE_TIME_SERIES_2 =
-      TimeSeriesGauge.create(Arrays.asList(LABEL_VALUE_1, LABEL_VALUE_2), Arrays.asList(POINT_2));
-  private static final TimeSeriesCumulative CUMULATIVE_TIME_SERIES =
-      TimeSeriesCumulative.create(
-          Arrays.asList(LABEL_VALUE_EMPTY), Arrays.asList(POINT_3), TIMESTAMP_1);
-  private static final TimeSeriesGaugeList TIME_SERIES_GAUGE_LIST =
-      TimeSeriesGaugeList.create(Arrays.asList(GAUGE_TIME_SERIES_1, GAUGE_TIME_SERIES_2));
-  private static final TimeSeriesCumulativeList TIME_SERIES_CUMULATIVE_LIST =
-      TimeSeriesCumulativeList.create(Arrays.asList(CUMULATIVE_TIME_SERIES));
+  private static final TimeSeries GAUGE_TIME_SERIES_1 =
+      TimeSeries.create(Arrays.asList(LABEL_VALUE_1, LABEL_VALUE_2), Arrays.asList(POINT_1), null);
+  private static final TimeSeries GAUGE_TIME_SERIES_2 =
+      TimeSeries.create(Arrays.asList(LABEL_VALUE_1, LABEL_VALUE_2), Arrays.asList(POINT_2), null);
+  private static final TimeSeries CUMULATIVE_TIME_SERIES =
+      TimeSeries.create(Arrays.asList(LABEL_VALUE_EMPTY), Arrays.asList(POINT_3), TIMESTAMP_1);
 
   @Test
   public void testGet() {
-    Metric metric = Metric.create(METRIC_DESCRIPTOR_1, TIME_SERIES_GAUGE_LIST);
+    Metric metric =
+        Metric.create(METRIC_DESCRIPTOR_1, Arrays.asList(GAUGE_TIME_SERIES_1, GAUGE_TIME_SERIES_2));
     assertThat(metric.getMetricDescriptor()).isEqualTo(METRIC_DESCRIPTOR_1);
-    assertThat(metric.getTimeSeriesList()).isEqualTo(TIME_SERIES_GAUGE_LIST);
+    assertThat(metric.getTimeSeriesList())
+        .containsExactly(GAUGE_TIME_SERIES_1, GAUGE_TIME_SERIES_2)
+        .inOrder();
   }
 
   @Test
-  public void typeMismatch_GaugeDouble_TimeSeriesCumulative() {
+  public void typeMismatch_GaugeDouble_Long() {
     typeMismatch(
         METRIC_DESCRIPTOR_1,
-        TIME_SERIES_CUMULATIVE_LIST,
-        String.format(
-            "Type mismatch: %s, %s.",
-            Type.GAUGE_DOUBLE, TIME_SERIES_CUMULATIVE_LIST.getClass().getSimpleName()));
+        Arrays.asList(CUMULATIVE_TIME_SERIES),
+        String.format("Type mismatch: %s, %s.", Type.GAUGE_DOUBLE, "ValueLong"));
   }
 
   @Test
-  public void typeMismatch_CumulativeInt64_TimeSeriesGauge() {
+  public void typeMismatch_CumulativeInt64_Double() {
     typeMismatch(
         METRIC_DESCRIPTOR_2,
-        TIME_SERIES_GAUGE_LIST,
-        String.format(
-            "Type mismatch: %s, %s.",
-            Type.CUMULATIVE_INT64, TIME_SERIES_GAUGE_LIST.getClass().getSimpleName()));
+        Arrays.asList(GAUGE_TIME_SERIES_1),
+        String.format("Type mismatch: %s, %s.", Type.CUMULATIVE_INT64, "ValueDouble"));
   }
 
   private void typeMismatch(
-      MetricDescriptor metricDescriptor, TimeSeriesList timeSeriesList, String errorMessage) {
+      MetricDescriptor metricDescriptor, List<TimeSeries> timeSeriesList, String errorMessage) {
     thrown.expect(IllegalArgumentException.class);
     thrown.expectMessage(errorMessage);
     Metric.create(metricDescriptor, timeSeriesList);
@@ -111,17 +104,13 @@ public class MetricTest {
   public void testEquals() {
     new EqualsTester()
         .addEqualityGroup(
-            Metric.create(METRIC_DESCRIPTOR_1, TIME_SERIES_GAUGE_LIST),
-            Metric.create(METRIC_DESCRIPTOR_1, TIME_SERIES_GAUGE_LIST))
-        .addEqualityGroup(
             Metric.create(
-                METRIC_DESCRIPTOR_1,
-                TimeSeriesGaugeList.create(Collections.<TimeSeriesGauge>emptyList())))
-        .addEqualityGroup(Metric.create(METRIC_DESCRIPTOR_2, TIME_SERIES_CUMULATIVE_LIST))
-        .addEqualityGroup(
+                METRIC_DESCRIPTOR_1, Arrays.asList(GAUGE_TIME_SERIES_1, GAUGE_TIME_SERIES_2)),
             Metric.create(
-                METRIC_DESCRIPTOR_2,
-                TimeSeriesCumulativeList.create(Collections.<TimeSeriesCumulative>emptyList())))
+                METRIC_DESCRIPTOR_1, Arrays.asList(GAUGE_TIME_SERIES_1, GAUGE_TIME_SERIES_2)))
+        .addEqualityGroup(Metric.create(METRIC_DESCRIPTOR_1, Collections.<TimeSeries>emptyList()))
+        .addEqualityGroup(Metric.create(METRIC_DESCRIPTOR_2, Arrays.asList(CUMULATIVE_TIME_SERIES)))
+        .addEqualityGroup(Metric.create(METRIC_DESCRIPTOR_2, Collections.<TimeSeries>emptyList()))
         .testEquals();
   }
 }
diff --git a/api/src/test/java/io/opencensus/metrics/TimeSeriesGaugeTest.java b/api/src/test/java/io/opencensus/metrics/TimeSeriesGaugeTest.java
deleted file mode 100644
index 83f7c267..00000000
--- a/api/src/test/java/io/opencensus/metrics/TimeSeriesGaugeTest.java
+++ /dev/null
@@ -1,104 +0,0 @@
-/*
- * Copyright 2018, OpenCensus Authors
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package io.opencensus.metrics;
-
-import static com.google.common.truth.Truth.assertThat;
-
-import com.google.common.testing.EqualsTester;
-import io.opencensus.common.Timestamp;
-import java.util.Arrays;
-import java.util.Collections;
-import java.util.List;
-import org.hamcrest.CoreMatchers;
-import org.junit.Rule;
-import org.junit.Test;
-import org.junit.rules.ExpectedException;
-import org.junit.runner.RunWith;
-import org.junit.runners.JUnit4;
-
-/** Unit tests for {@link TimeSeriesGauge}. */
-@RunWith(JUnit4.class)
-public class TimeSeriesGaugeTest {
-
-  @Rule public ExpectedException thrown = ExpectedException.none();
-
-  private static final LabelValue LABEL_VALUE_1 = LabelValue.create("value1");
-  private static final LabelValue LABEL_VALUE_2 = LabelValue.create("value2");
-  private static final Value VALUE_LONG = Value.longValue(12345678);
-  private static final Value VALUE_DOUBLE = Value.doubleValue(-345.77);
-  private static final Timestamp TIMESTAMP_1 = Timestamp.fromMillis(1000);
-  private static final Timestamp TIMESTAMP_2 = Timestamp.fromMillis(2000);
-  private static final Point POINT_1 = Point.create(VALUE_DOUBLE, TIMESTAMP_1);
-  private static final Point POINT_2 = Point.create(VALUE_LONG, TIMESTAMP_2);
-
-  @Test
-  public void testGet_TimeSeriesGauge() {
-    TimeSeriesGauge gaugeTimeSeries =
-        TimeSeriesGauge.create(
-            Arrays.asList(LABEL_VALUE_1, LABEL_VALUE_2), Arrays.asList(POINT_1, POINT_2));
-    assertThat(gaugeTimeSeries.getLabelValues())
-        .containsExactly(LABEL_VALUE_1, LABEL_VALUE_2)
-        .inOrder();
-    assertThat(gaugeTimeSeries.getPoints()).containsExactly(POINT_1, POINT_2).inOrder();
-  }
-
-  @Test
-  public void create_WithNullLabelValueList() {
-    thrown.expect(NullPointerException.class);
-    thrown.expectMessage(CoreMatchers.equalTo("labelValues"));
-    TimeSeriesGauge.create(null, Collections.<Point>emptyList());
-  }
-
-  @Test
-  public void create_WithNullLabelValue() {
-    List<LabelValue> labelValues = Arrays.asList(LABEL_VALUE_1, null);
-    thrown.expect(NullPointerException.class);
-    thrown.expectMessage(CoreMatchers.equalTo("labelValue"));
-    TimeSeriesGauge.create(labelValues, Collections.<Point>emptyList());
-  }
-
-  @Test
-  public void create_WithNullPointList() {
-    thrown.expect(NullPointerException.class);
-    thrown.expectMessage(CoreMatchers.equalTo("points"));
-    TimeSeriesGauge.create(Collections.<LabelValue>emptyList(), null);
-  }
-
-  @Test
-  public void create_WithNullPoint() {
-    List<Point> points = Arrays.asList(POINT_1, null);
-    thrown.expect(NullPointerException.class);
-    thrown.expectMessage(CoreMatchers.equalTo("point"));
-    TimeSeriesGauge.create(Collections.<LabelValue>emptyList(), points);
-  }
-
-  @Test
-  public void testEquals() {
-    new EqualsTester()
-        .addEqualityGroup(
-            TimeSeriesGauge.create(
-                Arrays.asList(LABEL_VALUE_1, LABEL_VALUE_2), Arrays.asList(POINT_1, POINT_2)),
-            TimeSeriesGauge.create(
-                Arrays.asList(LABEL_VALUE_1, LABEL_VALUE_2), Arrays.asList(POINT_1, POINT_2)))
-        .addEqualityGroup(
-            TimeSeriesGauge.create(
-                Arrays.asList(LABEL_VALUE_1, LABEL_VALUE_2), Arrays.asList(POINT_1)))
-        .addEqualityGroup(
-            TimeSeriesGauge.create(Arrays.asList(LABEL_VALUE_1), Arrays.asList(POINT_1)))
-        .testEquals();
-  }
-}
diff --git a/api/src/test/java/io/opencensus/metrics/TimeSeriesListTest.java b/api/src/test/java/io/opencensus/metrics/TimeSeriesListTest.java
deleted file mode 100644
index 46ace50f..00000000
--- a/api/src/test/java/io/opencensus/metrics/TimeSeriesListTest.java
+++ /dev/null
@@ -1,135 +0,0 @@
-/*
- * Copyright 2018, OpenCensus Authors
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package io.opencensus.metrics;
-
-import static com.google.common.truth.Truth.assertThat;
-
-import com.google.common.testing.EqualsTester;
-import io.opencensus.common.Functions;
-import io.opencensus.common.Timestamp;
-import io.opencensus.metrics.TimeSeriesList.TimeSeriesCumulativeList;
-import io.opencensus.metrics.TimeSeriesList.TimeSeriesGaugeList;
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Collections;
-import java.util.List;
-import org.hamcrest.CoreMatchers;
-import org.junit.Rule;
-import org.junit.Test;
-import org.junit.rules.ExpectedException;
-import org.junit.runner.RunWith;
-import org.junit.runners.JUnit4;
-
-/** Unit tests for {@link TimeSeries}. */
-@RunWith(JUnit4.class)
-public class TimeSeriesListTest {
-
-  @Rule public ExpectedException thrown = ExpectedException.none();
-
-  private static final LabelValue LABEL_VALUE_1 = LabelValue.create("value1");
-  private static final LabelValue LABEL_VALUE_2 = LabelValue.create("value2");
-  private static final LabelValue LABEL_VALUE_EMPTY = LabelValue.create("");
-  private static final Value VALUE_LONG = Value.longValue(12345678);
-  private static final Value VALUE_DOUBLE = Value.doubleValue(-345.77);
-  private static final Timestamp TIMESTAMP_1 = Timestamp.fromMillis(1000);
-  private static final Timestamp TIMESTAMP_2 = Timestamp.fromMillis(2000);
-  private static final Timestamp TIMESTAMP_3 = Timestamp.fromMillis(3000);
-  private static final Point POINT_1 = Point.create(VALUE_DOUBLE, TIMESTAMP_2);
-  private static final Point POINT_2 = Point.create(VALUE_LONG, TIMESTAMP_3);
-  private static final TimeSeriesGauge TIME_SERIES_GAUGE =
-      TimeSeriesGauge.create(
-          Arrays.asList(LABEL_VALUE_1, LABEL_VALUE_2), Arrays.asList(POINT_1, POINT_2));
-  private static final TimeSeriesCumulative TIME_SERIES_CUMULATIVE =
-      TimeSeriesCumulative.create(
-          Arrays.asList(LABEL_VALUE_1, LABEL_VALUE_EMPTY), Arrays.asList(POINT_1), TIMESTAMP_1);
-
-  @Test
-  public void testGet_TimeSeriesGaugeList() {
-    TimeSeriesGaugeList gaugeTimeSeriesList =
-        TimeSeriesGaugeList.create(Collections.singletonList(TIME_SERIES_GAUGE));
-    assertThat(gaugeTimeSeriesList.getList()).containsExactly(TIME_SERIES_GAUGE);
-  }
-
-  @Test
-  public void testGet_TimeSeriesCumulativeList() {
-    TimeSeriesCumulativeList cumulativeTimeSeriesList =
-        TimeSeriesCumulativeList.create(Collections.singletonList(TIME_SERIES_CUMULATIVE));
-    assertThat(cumulativeTimeSeriesList.getList()).containsExactly(TIME_SERIES_CUMULATIVE);
-  }
-
-  @Test
-  public void createGaugeList_WithNullList() {
-    thrown.expect(NullPointerException.class);
-    thrown.expectMessage(CoreMatchers.equalTo("list"));
-    TimeSeriesGaugeList.create(null);
-  }
-
-  @Test
-  public void createGaugeList_WithNullTimeSeries() {
-    thrown.expect(NullPointerException.class);
-    thrown.expectMessage(CoreMatchers.equalTo("timeSeriesGauge"));
-    TimeSeriesGaugeList.create(Arrays.asList(TIME_SERIES_GAUGE, null));
-  }
-
-  @Test
-  public void createCumulativeList_WithNullList() {
-    thrown.expect(NullPointerException.class);
-    thrown.expectMessage(CoreMatchers.equalTo("list"));
-    TimeSeriesCumulativeList.create(null);
-  }
-
-  @Test
-  public void createCumulativeList_WithNullTimeSeries() {
-    thrown.expect(NullPointerException.class);
-    thrown.expectMessage(CoreMatchers.equalTo("timeSeriesCumulative"));
-    TimeSeriesCumulativeList.create(Arrays.asList(TIME_SERIES_CUMULATIVE, null));
-  }
-
-  @Test
-  public void testEquals() {
-    new EqualsTester()
-        .addEqualityGroup(
-            TimeSeriesGaugeList.create(Collections.singletonList(TIME_SERIES_GAUGE)),
-            TimeSeriesGaugeList.create(Collections.singletonList(TIME_SERIES_GAUGE)))
-        .addEqualityGroup(
-            TimeSeriesCumulativeList.create(Collections.singletonList(TIME_SERIES_CUMULATIVE)),
-            TimeSeriesCumulativeList.create(Collections.singletonList(TIME_SERIES_CUMULATIVE)))
-        .addEqualityGroup(TimeSeriesGaugeList.create(Collections.<TimeSeriesGauge>emptyList()))
-        .addEqualityGroup(
-            TimeSeriesCumulativeList.create(Collections.<TimeSeriesCumulative>emptyList()))
-        .testEquals();
-  }
-
-  @Test
-  public void testMatch() {
-    TimeSeriesList gaugeTimeSeriesList =
-        TimeSeriesGaugeList.create(Collections.singletonList(TIME_SERIES_GAUGE));
-    TimeSeriesList cumulativeTimeSeriesList =
-        TimeSeriesCumulativeList.create(Collections.singletonList(TIME_SERIES_CUMULATIVE));
-
-    final List<String> actual = new ArrayList<String>();
-    for (TimeSeriesList timeSeriesList :
-        Arrays.asList(cumulativeTimeSeriesList, gaugeTimeSeriesList)) {
-      actual.add(
-          timeSeriesList.match(
-              Functions.returnConstant("TimeSeriesGaugeList"),
-              Functions.returnConstant("TimeSeriesCumulativeList"),
-              Functions.<String>throwAssertionError()));
-    }
-    assertThat(actual).containsExactly("TimeSeriesCumulativeList", "TimeSeriesGaugeList").inOrder();
-  }
-}
diff --git a/api/src/test/java/io/opencensus/metrics/TimeSeriesCumulativeTest.java b/api/src/test/java/io/opencensus/metrics/TimeSeriesTest.java
index 3532a5a5..07dff97d 100644
--- a/api/src/test/java/io/opencensus/metrics/TimeSeriesCumulativeTest.java
+++ b/api/src/test/java/io/opencensus/metrics/TimeSeriesTest.java
@@ -30,9 +30,9 @@ import org.junit.rules.ExpectedException;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
 
-/** Unit tests for {@link TimeSeriesCumulative}. */
+/** Unit tests for {@link TimeSeries}. */
 @RunWith(JUnit4.class)
-public class TimeSeriesCumulativeTest {
+public class TimeSeriesTest {
 
   @Rule public ExpectedException thrown = ExpectedException.none();
 
@@ -47,9 +47,9 @@ public class TimeSeriesCumulativeTest {
   private static final Point POINT_2 = Point.create(VALUE_LONG, TIMESTAMP_3);
 
   @Test
-  public void testGet_TimeSeriesCumulative() {
-    TimeSeriesCumulative cumulativeTimeSeries =
-        TimeSeriesCumulative.create(
+  public void testGet_TimeSeries() {
+    TimeSeries cumulativeTimeSeries =
+        TimeSeries.create(
             Arrays.asList(LABEL_VALUE_1, LABEL_VALUE_2), Arrays.asList(POINT_1), TIMESTAMP_1);
     assertThat(cumulativeTimeSeries.getStartTimestamp()).isEqualTo(TIMESTAMP_1);
     assertThat(cumulativeTimeSeries.getLabelValues())
@@ -62,7 +62,7 @@ public class TimeSeriesCumulativeTest {
   public void create_WithNullLabelValueList() {
     thrown.expect(NullPointerException.class);
     thrown.expectMessage(CoreMatchers.equalTo("labelValues"));
-    TimeSeriesCumulative.create(null, Collections.<Point>emptyList(), TIMESTAMP_1);
+    TimeSeries.create(null, Collections.<Point>emptyList(), TIMESTAMP_1);
   }
 
   @Test
@@ -70,14 +70,14 @@ public class TimeSeriesCumulativeTest {
     List<LabelValue> labelValues = Arrays.asList(LABEL_VALUE_1, null);
     thrown.expect(NullPointerException.class);
     thrown.expectMessage(CoreMatchers.equalTo("labelValue"));
-    TimeSeriesCumulative.create(labelValues, Collections.<Point>emptyList(), TIMESTAMP_1);
+    TimeSeries.create(labelValues, Collections.<Point>emptyList(), TIMESTAMP_1);
   }
 
   @Test
   public void create_WithNullPointList() {
     thrown.expect(NullPointerException.class);
     thrown.expectMessage(CoreMatchers.equalTo("points"));
-    TimeSeriesCumulative.create(Collections.<LabelValue>emptyList(), null, TIMESTAMP_1);
+    TimeSeries.create(Collections.<LabelValue>emptyList(), null, TIMESTAMP_1);
   }
 
   @Test
@@ -85,28 +85,31 @@ public class TimeSeriesCumulativeTest {
     List<Point> points = Arrays.asList(POINT_1, null);
     thrown.expect(NullPointerException.class);
     thrown.expectMessage(CoreMatchers.equalTo("point"));
-    TimeSeriesCumulative.create(Collections.<LabelValue>emptyList(), points, TIMESTAMP_1);
+    TimeSeries.create(Collections.<LabelValue>emptyList(), points, TIMESTAMP_1);
   }
 
   @Test
   public void testEquals() {
     new EqualsTester()
         .addEqualityGroup(
-            TimeSeriesCumulative.create(
+            TimeSeries.create(
                 Arrays.asList(LABEL_VALUE_1, LABEL_VALUE_2), Arrays.asList(POINT_1), TIMESTAMP_1),
-            TimeSeriesCumulative.create(
+            TimeSeries.create(
                 Arrays.asList(LABEL_VALUE_1, LABEL_VALUE_2), Arrays.asList(POINT_1), TIMESTAMP_1))
         .addEqualityGroup(
-            TimeSeriesCumulative.create(
+            TimeSeries.create(
+                Arrays.asList(LABEL_VALUE_1, LABEL_VALUE_2), Arrays.asList(POINT_1), null),
+            TimeSeries.create(
+                Arrays.asList(LABEL_VALUE_1, LABEL_VALUE_2), Arrays.asList(POINT_1), null))
+        .addEqualityGroup(
+            TimeSeries.create(
                 Arrays.asList(LABEL_VALUE_1, LABEL_VALUE_2), Arrays.asList(POINT_1), TIMESTAMP_2))
         .addEqualityGroup(
-            TimeSeriesCumulative.create(
-                Arrays.asList(LABEL_VALUE_1), Arrays.asList(POINT_1), TIMESTAMP_2))
+            TimeSeries.create(Arrays.asList(LABEL_VALUE_1), Arrays.asList(POINT_1), TIMESTAMP_2))
         .addEqualityGroup(
-            TimeSeriesCumulative.create(
-                Arrays.asList(LABEL_VALUE_1), Arrays.asList(POINT_2), TIMESTAMP_2))
+            TimeSeries.create(Arrays.asList(LABEL_VALUE_1), Arrays.asList(POINT_2), TIMESTAMP_2))
         .addEqualityGroup(
-            TimeSeriesCumulative.create(
+            TimeSeries.create(
                 Arrays.asList(LABEL_VALUE_1), Arrays.asList(POINT_1, POINT_2), TIMESTAMP_2))
         .testEquals();
   }
diff --git a/impl_core/src/main/java/io/opencensus/implcore/metrics/Gauge.java b/impl_core/src/main/java/io/opencensus/implcore/metrics/Gauge.java
index 0a3c68b3..e6498066 100644
--- a/impl_core/src/main/java/io/opencensus/implcore/metrics/Gauge.java
+++ b/impl_core/src/main/java/io/opencensus/implcore/metrics/Gauge.java
@@ -27,8 +27,7 @@ import io.opencensus.metrics.Metric;
 import io.opencensus.metrics.MetricDescriptor;
 import io.opencensus.metrics.MetricDescriptor.Type;
 import io.opencensus.metrics.Point;
-import io.opencensus.metrics.TimeSeriesGauge;
-import io.opencensus.metrics.TimeSeriesList;
+import io.opencensus.metrics.TimeSeries;
 import io.opencensus.metrics.Value;
 import java.util.Collections;
 import java.util.List;
@@ -38,13 +37,10 @@ abstract class Gauge {
   private final List<LabelValue> labelValues;
 
   final Metric getMetric(Clock clock) {
-    return Metric.create(
-        metricDescriptor,
-        TimeSeriesList.TimeSeriesGaugeList.create(
-            Collections.singletonList(getTimeSeriesGauge(clock))));
+    return Metric.create(metricDescriptor, Collections.singletonList(getTimeSeries(clock)));
   }
 
-  abstract TimeSeriesGauge getTimeSeriesGauge(Clock clock);
+  abstract TimeSeries getTimeSeries(Clock clock);
 
   static final class DoubleGauge<T> extends Gauge {
     private final T obj;
@@ -66,11 +62,12 @@ abstract class Gauge {
     }
 
     @Override
-    TimeSeriesGauge getTimeSeriesGauge(Clock clock) {
-      return TimeSeriesGauge.create(
+    TimeSeries getTimeSeries(Clock clock) {
+      return TimeSeries.create(
           getLabelValues(),
           Collections.singletonList(
-              Point.create(Value.doubleValue(function.applyAsDouble(obj)), clock.now())));
+              Point.create(Value.doubleValue(function.applyAsDouble(obj)), clock.now())),
+          null);
     }
   }
 
@@ -94,11 +91,12 @@ abstract class Gauge {
     }
 
     @Override
-    TimeSeriesGauge getTimeSeriesGauge(Clock clock) {
-      return TimeSeriesGauge.create(
+    TimeSeries getTimeSeries(Clock clock) {
+      return TimeSeries.create(
           getLabelValues(),
           Collections.singletonList(
-              Point.create(Value.longValue(function.applyAsLong(obj)), clock.now())));
+              Point.create(Value.longValue(function.applyAsLong(obj)), clock.now())),
+          null);
     }
   }
 
diff --git a/impl_core/src/main/java/io/opencensus/implcore/stats/MutableViewData.java b/impl_core/src/main/java/io/opencensus/implcore/stats/MutableViewData.java
index 944cdc93..7368a161 100644
--- a/impl_core/src/main/java/io/opencensus/implcore/stats/MutableViewData.java
+++ b/impl_core/src/main/java/io/opencensus/implcore/stats/MutableViewData.java
@@ -37,10 +37,7 @@ import io.opencensus.metrics.Metric;
 import io.opencensus.metrics.MetricDescriptor;
 import io.opencensus.metrics.MetricDescriptor.Type;
 import io.opencensus.metrics.Point;
-import io.opencensus.metrics.TimeSeriesCumulative;
-import io.opencensus.metrics.TimeSeriesGauge;
-import io.opencensus.metrics.TimeSeriesList.TimeSeriesCumulativeList;
-import io.opencensus.metrics.TimeSeriesList.TimeSeriesGaugeList;
+import io.opencensus.metrics.TimeSeries;
 import io.opencensus.stats.Aggregation;
 import io.opencensus.stats.AggregationData;
 import io.opencensus.stats.Measure;
@@ -134,34 +131,18 @@ abstract class MutableViewData {
       if (state == State.DISABLED) {
         return null;
       }
-      // TODO(bdrutu): Refactor this after TimeSeriesGauge and TimeSeriesCumulative are combined.
       Type type = metricDescriptor.getType();
-      if (type == Type.GAUGE_INT64 || type == Type.GAUGE_DOUBLE) {
-        List<TimeSeriesGauge> timeSeriesGauges = new ArrayList<TimeSeriesGauge>();
-        for (Entry<List</*@Nullable*/ TagValue>, MutableAggregation> entry :
-            tagValueAggregationMap.entrySet()) {
-          List<LabelValue> labelValues = MetricUtils.tagValuesToLabelValues(entry.getKey());
-          Point point = entry.getValue().toPoint(now);
-          timeSeriesGauges.add(
-              TimeSeriesGauge.create(labelValues, Collections.singletonList(point)));
-        }
-        return Metric.create(metricDescriptor, TimeSeriesGaugeList.create(timeSeriesGauges));
-      } else {
-        List<TimeSeriesCumulative> timeSeriesCumulatives = new ArrayList<TimeSeriesCumulative>();
-        for (Entry<
-                List<
-                    /*@Nullable*/
-                    TagValue>,
-                MutableAggregation>
-            entry : tagValueAggregationMap.entrySet()) {
-          List<LabelValue> labelValues = MetricUtils.tagValuesToLabelValues(entry.getKey());
-          Point point = entry.getValue().toPoint(now);
-          timeSeriesCumulatives.add(
-              TimeSeriesCumulative.create(labelValues, Collections.singletonList(point), start));
-        }
-        return Metric.create(
-            metricDescriptor, TimeSeriesCumulativeList.create(timeSeriesCumulatives));
+      @javax.annotation.Nullable
+      Timestamp startTime = type == Type.GAUGE_INT64 || type == Type.GAUGE_DOUBLE ? null : start;
+      List<TimeSeries> timeSeriesList = new ArrayList<TimeSeries>();
+      for (Entry<List</*@Nullable*/ TagValue>, MutableAggregation> entry :
+          tagValueAggregationMap.entrySet()) {
+        List<LabelValue> labelValues = MetricUtils.tagValuesToLabelValues(entry.getKey());
+        Point point = entry.getValue().toPoint(now);
+        timeSeriesList.add(
+            TimeSeries.create(labelValues, Collections.singletonList(point), startTime));
       }
+      return Metric.create(metricDescriptor, timeSeriesList);
     }
 
     @Override
diff --git a/impl_core/src/test/java/io/opencensus/implcore/metrics/GaugeTest.java b/impl_core/src/test/java/io/opencensus/implcore/metrics/GaugeTest.java
index 1f6a1881..e1c17876 100644
--- a/impl_core/src/test/java/io/opencensus/implcore/metrics/GaugeTest.java
+++ b/impl_core/src/test/java/io/opencensus/implcore/metrics/GaugeTest.java
@@ -29,8 +29,7 @@ import io.opencensus.metrics.Metric;
 import io.opencensus.metrics.MetricDescriptor;
 import io.opencensus.metrics.MetricDescriptor.Type;
 import io.opencensus.metrics.Point;
-import io.opencensus.metrics.TimeSeriesGauge;
-import io.opencensus.metrics.TimeSeriesList;
+import io.opencensus.metrics.TimeSeries;
 import io.opencensus.metrics.Value;
 import io.opencensus.testing.common.TestClock;
 import java.util.Collections;
@@ -89,12 +88,12 @@ public class GaugeTest {
         .isEqualTo(
             Metric.create(
                 MetricDescriptor.create(NAME, DESCRIPTION, UNIT, Type.GAUGE_INT64, LABEL_KEYS),
-                TimeSeriesList.TimeSeriesGaugeList.create(
-                    Collections.singletonList(
-                        TimeSeriesGauge.create(
-                            LABEL_VALUES,
-                            Collections.singletonList(
-                                Point.create(Value.longValue(OBJ.hashCode()), TEST_TIME)))))));
+                Collections.singletonList(
+                    TimeSeries.create(
+                        LABEL_VALUES,
+                        Collections.singletonList(
+                            Point.create(Value.longValue(OBJ.hashCode()), TEST_TIME)),
+                        null))));
   }
 
   @Test
@@ -103,11 +102,11 @@ public class GaugeTest {
         .isEqualTo(
             Metric.create(
                 MetricDescriptor.create(NAME, DESCRIPTION, UNIT, Type.GAUGE_DOUBLE, LABEL_KEYS),
-                TimeSeriesList.TimeSeriesGaugeList.create(
-                    Collections.singletonList(
-                        TimeSeriesGauge.create(
-                            LABEL_VALUES,
-                            Collections.singletonList(
-                                Point.create(Value.doubleValue(OBJ.hashCode()), TEST_TIME)))))));
+                Collections.singletonList(
+                    TimeSeries.create(
+                        LABEL_VALUES,
+                        Collections.singletonList(
+                            Point.create(Value.doubleValue(OBJ.hashCode()), TEST_TIME)),
+                        null))));
   }
 }
diff --git a/impl_core/src/test/java/io/opencensus/implcore/metrics/MetricRegistryImplTest.java b/impl_core/src/test/java/io/opencensus/implcore/metrics/MetricRegistryImplTest.java
index fdab47aa..769efab2 100644
--- a/impl_core/src/test/java/io/opencensus/implcore/metrics/MetricRegistryImplTest.java
+++ b/impl_core/src/test/java/io/opencensus/implcore/metrics/MetricRegistryImplTest.java
@@ -27,8 +27,7 @@ import io.opencensus.metrics.Metric;
 import io.opencensus.metrics.MetricDescriptor;
 import io.opencensus.metrics.MetricDescriptor.Type;
 import io.opencensus.metrics.Point;
-import io.opencensus.metrics.TimeSeriesGauge;
-import io.opencensus.metrics.TimeSeriesList;
+import io.opencensus.metrics.TimeSeries;
 import io.opencensus.metrics.Value;
 import io.opencensus.testing.common.TestClock;
 import java.util.Collections;
@@ -159,12 +158,11 @@ public class MetricRegistryImplTest {
                     UNIT,
                     Type.GAUGE_DOUBLE,
                     Collections.unmodifiableList(Collections.singletonList(LABEL_KEY))),
-                TimeSeriesList.TimeSeriesGaugeList.create(
-                    Collections.singletonList(
-                        TimeSeriesGauge.create(
-                            Collections.unmodifiableList(Collections.singletonList(LABEL_VALUES)),
-                            Collections.singletonList(
-                                Point.create(Value.doubleValue(5.0), TEST_TIME)))))));
+                Collections.singletonList(
+                    TimeSeries.create(
+                        Collections.unmodifiableList(Collections.singletonList(LABEL_VALUES)),
+                        Collections.singletonList(Point.create(Value.doubleValue(5.0), TEST_TIME)),
+                        null))));
   }
 
   @Test
@@ -264,12 +262,11 @@ public class MetricRegistryImplTest {
                     UNIT,
                     Type.GAUGE_INT64,
                     Collections.unmodifiableList(Collections.singletonList(LABEL_KEY))),
-                TimeSeriesList.TimeSeriesGaugeList.create(
-                    Collections.singletonList(
-                        TimeSeriesGauge.create(
-                            Collections.unmodifiableList(Collections.singletonList(LABEL_VALUES)),
-                            Collections.singletonList(
-                                Point.create(Value.longValue(7), TEST_TIME)))))));
+                Collections.singletonList(
+                    TimeSeries.create(
+                        Collections.unmodifiableList(Collections.singletonList(LABEL_VALUES)),
+                        Collections.singletonList(Point.create(Value.longValue(7), TEST_TIME)),
+                        null))));
   }
 
   @Test
@@ -307,12 +304,11 @@ public class MetricRegistryImplTest {
                     UNIT,
                     Type.GAUGE_INT64,
                     Collections.unmodifiableList(Collections.singletonList(LABEL_KEY))),
-                TimeSeriesList.TimeSeriesGaugeList.create(
-                    Collections.singletonList(
-                        TimeSeriesGauge.create(
-                            Collections.unmodifiableList(Collections.singletonList(LABEL_VALUES)),
-                            Collections.singletonList(
-                                Point.create(Value.longValue(7), TEST_TIME)))))),
+                Collections.singletonList(
+                    TimeSeries.create(
+                        Collections.unmodifiableList(Collections.singletonList(LABEL_VALUES)),
+                        Collections.singletonList(Point.create(Value.longValue(7), TEST_TIME)),
+                        null))),
             Metric.create(
                 MetricDescriptor.create(
                     NAME,
@@ -320,12 +316,11 @@ public class MetricRegistryImplTest {
                     UNIT,
                     Type.GAUGE_DOUBLE,
                     Collections.unmodifiableList(Collections.singletonList(LABEL_KEY))),
-                TimeSeriesList.TimeSeriesGaugeList.create(
-                    Collections.singletonList(
-                        TimeSeriesGauge.create(
-                            Collections.unmodifiableList(Collections.singletonList(LABEL_VALUES)),
-                            Collections.singletonList(
-                                Point.create(Value.doubleValue(5.0), TEST_TIME)))))));
+                Collections.singletonList(
+                    TimeSeries.create(
+                        Collections.unmodifiableList(Collections.singletonList(LABEL_VALUES)),
+                        Collections.singletonList(Point.create(Value.doubleValue(5.0), TEST_TIME)),
+                        null))));
   }
 
   @Test