Metrics/TimeSeries: Add createWithOnePoint method to accept only one … (#1486)

* Metrics/TimeSeries: Add createWithOnePoint method to accept only one point

* Fix reviews

* Minor Fix

7 files changed, 101 insertions, 50 deletions

diff --git a/api/src/main/java/io/opencensus/metrics/export/TimeSeries.java b/api/src/main/java/io/opencensus/metrics/export/TimeSeries.java
index 959f55ba..bfaeae98 100644
--- a/api/src/main/java/io/opencensus/metrics/export/TimeSeries.java
+++ b/api/src/main/java/io/opencensus/metrics/export/TimeSeries.java
@@ -52,14 +52,45 @@ public abstract class TimeSeries {
    */
   public static TimeSeries create(
       List<LabelValue> labelValues, List<Point> points, @Nullable Timestamp startTimestamp) {
+    Utils.checkNotNull(points, "points");
+    Utils.checkListElementNotNull(points, "point");
+    return createInternal(
+        labelValues, Collections.unmodifiableList(new ArrayList<Point>(points)), startTimestamp);
+  }
+
+  /**
+   * Creates a {@link TimeSeries}.
+   *
+   * @param labelValues the {@code LabelValue}s that uniquely identify this {@code TimeSeries}.
+   * @param point the single data {@code Point} 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 0.17
+   */
+  public static TimeSeries createWithOnePoint(
+      List<LabelValue> labelValues, Point point, @Nullable Timestamp startTimestamp) {
+    Utils.checkNotNull(point, "point");
+    return createInternal(labelValues, Collections.singletonList(point), startTimestamp);
+  }
+
+  /**
+   * 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}.
+   */
+  private static TimeSeries createInternal(
+      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)),
+        points,
         startTimestamp);
   }
 
diff --git a/api/src/test/java/io/opencensus/metrics/export/TimeSeriesTest.java b/api/src/test/java/io/opencensus/metrics/export/TimeSeriesTest.java
index 31812549..92a2c8cf 100644
--- a/api/src/test/java/io/opencensus/metrics/export/TimeSeriesTest.java
+++ b/api/src/test/java/io/opencensus/metrics/export/TimeSeriesTest.java
@@ -90,6 +90,40 @@ public class TimeSeriesTest {
   }
 
   @Test
+  public void testGet_WithOnePointTimeSeries() {
+    TimeSeries cumulativeTimeSeries =
+        TimeSeries.createWithOnePoint(
+            Arrays.asList(LABEL_VALUE_1, LABEL_VALUE_2), POINT_1, TIMESTAMP_1);
+    assertThat(cumulativeTimeSeries.getStartTimestamp()).isEqualTo(TIMESTAMP_1);
+    assertThat(cumulativeTimeSeries.getLabelValues())
+        .containsExactly(LABEL_VALUE_1, LABEL_VALUE_2)
+        .inOrder();
+    assertThat(cumulativeTimeSeries.getPoints()).containsExactly(POINT_1).inOrder();
+  }
+
+  @Test
+  public void createWithOnePoint_WithNullLabelValueList() {
+    thrown.expect(NullPointerException.class);
+    thrown.expectMessage(CoreMatchers.equalTo("labelValues"));
+    TimeSeries.createWithOnePoint(null, POINT_1, TIMESTAMP_1);
+  }
+
+  @Test
+  public void createWithOnePoint_WithNullLabelValue() {
+    List<LabelValue> labelValues = Arrays.asList(LABEL_VALUE_1, null);
+    thrown.expect(NullPointerException.class);
+    thrown.expectMessage(CoreMatchers.equalTo("labelValue"));
+    TimeSeries.createWithOnePoint(labelValues, POINT_1, TIMESTAMP_1);
+  }
+
+  @Test
+  public void createWithOnePoint_WithNullPointList() {
+    thrown.expect(NullPointerException.class);
+    thrown.expectMessage(CoreMatchers.equalTo("point"));
+    TimeSeries.createWithOnePoint(Collections.<LabelValue>emptyList(), null, TIMESTAMP_1);
+  }
+
+  @Test
   public void testEquals() {
     new EqualsTester()
         .addEqualityGroup(
diff --git a/contrib/dropwizard/src/main/java/io/opencensus/contrib/dropwizard/DropWizardMetrics.java b/contrib/dropwizard/src/main/java/io/opencensus/contrib/dropwizard/DropWizardMetrics.java
index 7cc52d3f..246be801 100644
--- a/contrib/dropwizard/src/main/java/io/opencensus/contrib/dropwizard/DropWizardMetrics.java
+++ b/contrib/dropwizard/src/main/java/io/opencensus/contrib/dropwizard/DropWizardMetrics.java
@@ -127,10 +127,8 @@ public class DropWizardMetrics extends MetricProducer {
         MetricDescriptor.create(
             metricName, metricDescription, DEFAULT_UNIT, type, Collections.<LabelKey>emptyList());
     TimeSeries timeSeries =
-        TimeSeries.create(
-            Collections.<LabelValue>emptyList(),
-            Collections.singletonList(Point.create(value, clock.now())),
-            null);
+        TimeSeries.createWithOnePoint(
+            Collections.<LabelValue>emptyList(), Point.create(value, clock.now()), null);
     return Metric.create(metricDescriptor, Collections.singletonList(timeSeries));
   }
 
@@ -154,10 +152,9 @@ public class DropWizardMetrics extends MetricProducer {
             Type.GAUGE_INT64,
             Collections.<LabelKey>emptyList());
     TimeSeries timeSeries =
-        TimeSeries.create(
+        TimeSeries.createWithOnePoint(
             Collections.<LabelValue>emptyList(),
-            Collections.singletonList(
-                Point.create(Value.longValue(counter.getCount()), clock.now())),
+            Point.create(Value.longValue(counter.getCount()), clock.now()),
             null);
     return Metric.create(metricDescriptor, Collections.singletonList(timeSeries));
   }
@@ -181,9 +178,9 @@ public class DropWizardMetrics extends MetricProducer {
             Type.CUMULATIVE_INT64,
             Collections.<LabelKey>emptyList());
     TimeSeries countTimeSeries =
-        TimeSeries.create(
+        TimeSeries.createWithOnePoint(
             Collections.<LabelValue>emptyList(),
-            Collections.singletonList(Point.create(Value.longValue(meter.getCount()), clock.now())),
+            Point.create(Value.longValue(meter.getCount()), clock.now()),
             null);
 
     // Collect rate related metric
@@ -196,25 +193,21 @@ public class DropWizardMetrics extends MetricProducer {
 
     List<TimeSeries> timeSeriesList =
         Arrays.asList(
-            TimeSeries.create(
+            TimeSeries.createWithOnePoint(
                 RATE_MEAN_LABEL_VALUE,
-                Collections.singletonList(
-                    Point.create(Value.doubleValue(meter.getMeanRate()), clock.now())),
+                Point.create(Value.doubleValue(meter.getMeanRate()), clock.now()),
                 null),
-            TimeSeries.create(
+            TimeSeries.createWithOnePoint(
                 RATE_ONE_MINUTE_LABEL_VALUE,
-                Collections.singletonList(
-                    Point.create(Value.doubleValue(meter.getOneMinuteRate()), clock.now())),
+                Point.create(Value.doubleValue(meter.getOneMinuteRate()), clock.now()),
                 null),
-            TimeSeries.create(
+            TimeSeries.createWithOnePoint(
                 RATE_FIVE_MINUTE_LABEL_VALUE,
-                Collections.singletonList(
-                    Point.create(Value.doubleValue(meter.getFiveMinuteRate()), clock.now())),
+                Point.create(Value.doubleValue(meter.getFiveMinuteRate()), clock.now()),
                 null),
-            TimeSeries.create(
+            TimeSeries.createWithOnePoint(
                 RATE_FIFTEEN_MINUTE_LABEL_VALUE,
-                Collections.singletonList(
-                    Point.create(Value.doubleValue(meter.getFifteenMinuteRate()), clock.now())),
+                Point.create(Value.doubleValue(meter.getFifteenMinuteRate()), clock.now()),
                 null));
 
     return Collections.unmodifiableList(
@@ -287,10 +280,8 @@ public class DropWizardMetrics extends MetricProducer {
             Type.SUMMARY,
             Collections.<LabelKey>emptyList());
     TimeSeries timeSeries =
-        TimeSeries.create(
-            Collections.<LabelValue>emptyList(),
-            Collections.singletonList(point),
-            cumulativeStartTimestamp);
+        TimeSeries.createWithOnePoint(
+            Collections.<LabelValue>emptyList(), point, cumulativeStartTimestamp);
 
     return Metric.create(metricDescriptor, Collections.singletonList(timeSeries));
   }
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 30e5bf36..06cfbc1e 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
@@ -63,10 +63,9 @@ abstract class Gauge {
 
     @Override
     TimeSeries getTimeSeries(Clock clock) {
-      return TimeSeries.create(
+      return TimeSeries.createWithOnePoint(
           getLabelValues(),
-          Collections.singletonList(
-              Point.create(Value.doubleValue(function.applyAsDouble(obj)), clock.now())),
+          Point.create(Value.doubleValue(function.applyAsDouble(obj)), clock.now()),
           null);
     }
   }
@@ -92,10 +91,9 @@ abstract class Gauge {
 
     @Override
     TimeSeries getTimeSeries(Clock clock) {
-      return TimeSeries.create(
+      return TimeSeries.createWithOnePoint(
           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 0d25b292..928675e9 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
@@ -139,8 +139,7 @@ abstract class MutableViewData {
           tagValueAggregationMap.entrySet()) {
         List<LabelValue> labelValues = MetricUtils.tagValuesToLabelValues(entry.getKey());
         Point point = entry.getValue().toPoint(now);
-        timeSeriesList.add(
-            TimeSeries.create(labelValues, Collections.singletonList(point), startTime));
+        timeSeriesList.add(TimeSeries.createWithOnePoint(labelValues, point, startTime));
       }
       return Metric.create(metricDescriptor, timeSeriesList);
     }
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 161ad348..e5e4cbc5 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
@@ -89,10 +89,9 @@ public class GaugeTest {
             Metric.create(
                 MetricDescriptor.create(NAME, DESCRIPTION, UNIT, Type.GAUGE_INT64, LABEL_KEYS),
                 Collections.singletonList(
-                    TimeSeries.create(
+                    TimeSeries.createWithOnePoint(
                         LABEL_VALUES,
-                        Collections.singletonList(
-                            Point.create(Value.longValue(OBJ.hashCode()), TEST_TIME)),
+                        Point.create(Value.longValue(OBJ.hashCode()), TEST_TIME),
                         null))));
   }
 
@@ -103,10 +102,9 @@ public class GaugeTest {
             Metric.create(
                 MetricDescriptor.create(NAME, DESCRIPTION, UNIT, Type.GAUGE_DOUBLE, LABEL_KEYS),
                 Collections.singletonList(
-                    TimeSeries.create(
+                    TimeSeries.createWithOnePoint(
                         LABEL_VALUES,
-                        Collections.singletonList(
-                            Point.create(Value.doubleValue(OBJ.hashCode()), TEST_TIME)),
+                        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 3a5cb493..5210b266 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
@@ -159,9 +159,9 @@ public class MetricRegistryImplTest {
                     Type.GAUGE_DOUBLE,
                     Collections.unmodifiableList(Collections.singletonList(LABEL_KEY))),
                 Collections.singletonList(
-                    TimeSeries.create(
+                    TimeSeries.createWithOnePoint(
                         Collections.unmodifiableList(Collections.singletonList(LABEL_VALUES)),
-                        Collections.singletonList(Point.create(Value.doubleValue(5.0), TEST_TIME)),
+                        Point.create(Value.doubleValue(5.0), TEST_TIME),
                         null))));
   }
 
@@ -263,9 +263,9 @@ public class MetricRegistryImplTest {
                     Type.GAUGE_INT64,
                     Collections.unmodifiableList(Collections.singletonList(LABEL_KEY))),
                 Collections.singletonList(
-                    TimeSeries.create(
+                    TimeSeries.createWithOnePoint(
                         Collections.unmodifiableList(Collections.singletonList(LABEL_VALUES)),
-                        Collections.singletonList(Point.create(Value.longValue(7), TEST_TIME)),
+                        Point.create(Value.longValue(7), TEST_TIME),
                         null))));
   }
 
@@ -305,9 +305,9 @@ public class MetricRegistryImplTest {
                     Type.GAUGE_INT64,
                     Collections.unmodifiableList(Collections.singletonList(LABEL_KEY))),
                 Collections.singletonList(
-                    TimeSeries.create(
+                    TimeSeries.createWithOnePoint(
                         Collections.unmodifiableList(Collections.singletonList(LABEL_VALUES)),
-                        Collections.singletonList(Point.create(Value.longValue(7), TEST_TIME)),
+                        Point.create(Value.longValue(7), TEST_TIME),
                         null))),
             Metric.create(
                 MetricDescriptor.create(
@@ -317,9 +317,9 @@ public class MetricRegistryImplTest {
                     Type.GAUGE_DOUBLE,
                     Collections.unmodifiableList(Collections.singletonList(LABEL_KEY))),
                 Collections.singletonList(
-                    TimeSeries.create(
+                    TimeSeries.createWithOnePoint(
                         Collections.unmodifiableList(Collections.singletonList(LABEL_VALUES)),
-                        Collections.singletonList(Point.create(Value.doubleValue(5.0), TEST_TIME)),
+                        Point.create(Value.doubleValue(5.0), TEST_TIME),
                         null))));
   }