Count metrics should have unit '1'. (#1942)

Author: songy23

impl_core/src/main/java/io/opencensus/implcore/stats/MetricUtils.java

@@ -25,6 +25,7 @@
 import io.opencensus.metrics.export.MetricDescriptor;
 import io.opencensus.metrics.export.MetricDescriptor.Type;
 import io.opencensus.stats.Aggregation;
+import io.opencensus.stats.Aggregation.Count;
 import io.opencensus.stats.Measure;
 import io.opencensus.stats.View;
 import io.opencensus.tags.TagKey;
@@ -42,6 +43,8 @@
 // Utils to convert Stats data models to Metric data models.
 final class MetricUtils {
 
+  @VisibleForTesting static final String COUNT_UNIT = "1";
+
   @javax.annotation.Nullable
   static MetricDescriptor viewToMetricDescriptor(View view) {
     if (view.getWindow() instanceof View.AggregationWindow.Interval) {
@@ -54,11 +57,12 @@ static MetricDescriptor viewToMetricDescriptor(View view) {
       labelKeys.add(LabelKey.create(tagKey.getName(), ""));
     }
     Measure measure = view.getMeasure();
+    Aggregation aggregation = view.getAggregation();
     return MetricDescriptor.create(
         view.getName().asString(),
         view.getDescription(),
-        measure.getUnit(),
-        getType(measure, view.getAggregation()),
+        getUnit(measure, aggregation),
+        getType(measure, aggregation),
         labelKeys);
   }
 
@@ -80,6 +84,13 @@ static Type getType(Measure measure, Aggregation aggregation) {
         AGGREGATION_TYPE_DEFAULT_FUNCTION);
   }
 
+  private static String getUnit(Measure measure, Aggregation aggregation) {
+    if (aggregation instanceof Count) {
+      return COUNT_UNIT;
+    }
+    return measure.getUnit();
+  }
+
   static List<LabelValue> tagValuesToLabelValues(List</*@Nullable*/ TagValue> tagValues) {
     List<LabelValue> labelValues = new ArrayList<LabelValue>();
     for (/*@Nullable*/ TagValue tagValue : tagValues) {

impl_core/src/test/java/io/opencensus/implcore/stats/MetricUtilsTest.java

@@ -81,6 +81,9 @@ public class MetricUtilsTest {
           MEAN,
           Collections.singletonList(KEY),
           INTERVAL);
+  private static final View VIEW_3 =
+      View.create(
+          VIEW_NAME, VIEW_DESCRIPTION, MEASURE_DOUBLE, COUNT, Collections.singletonList(KEY));
 
   @Test
   public void viewToMetricDescriptor() {
@@ -93,6 +96,17 @@ public void viewToMetricDescriptor() {
     assertThat(metricDescriptor.getLabelKeys()).containsExactly(LabelKey.create(KEY.getName(), ""));
   }
 
+  @Test
+  public void viewToMetricDescriptor_Count() {
+    MetricDescriptor metricDescriptor = MetricUtils.viewToMetricDescriptor(VIEW_3);
+    assertThat(metricDescriptor).isNotNull();
+    assertThat(metricDescriptor.getName()).isEqualTo(VIEW_NAME.asString());
+    assertThat(metricDescriptor.getUnit()).isEqualTo(MetricUtils.COUNT_UNIT);
+    assertThat(metricDescriptor.getType()).isEqualTo(Type.CUMULATIVE_INT64);
+    assertThat(metricDescriptor.getDescription()).isEqualTo(VIEW_DESCRIPTION);
+    assertThat(metricDescriptor.getLabelKeys()).containsExactly(LabelKey.create(KEY.getName(), ""));
+  }
+
   @Test
   public void viewToMetricDescriptor_NoIntervalViews() {
     MetricDescriptor metricDescriptor = MetricUtils.viewToMetricDescriptor(VIEW_2);