Plugs-in the DoubleGauge into the registry (#1503)

3 files changed, 77 insertions, 5 deletions

diff --git a/api/src/main/java/io/opencensus/metrics/DoubleGauge.java b/api/src/main/java/io/opencensus/metrics/DoubleGauge.java
index de2b053b..32759973 100644
--- a/api/src/main/java/io/opencensus/metrics/DoubleGauge.java
+++ b/api/src/main/java/io/opencensus/metrics/DoubleGauge.java
@@ -32,7 +32,7 @@ import javax.annotation.concurrent.ThreadSafe;
  *   private static final MetricRegistry metricRegistry = Metrics.getMetricRegistry();
  *
  *   List<LabelKey> labelKeys = Arrays.asList(LabelKey.create("Name", "desc"));
- *   // TODO(mayurkale): Plugs-in the DoubleGauge into the registry.
+ *
  *   DoubleGauge gauge = metricRegistry.addDoubleGauge("queue_size",
  *                       "Pending jobs", "1", labelKeys);
  *
@@ -57,7 +57,6 @@ import javax.annotation.concurrent.ThreadSafe;
  *   List<LabelKey> labelKeys = Arrays.asList(LabelKey.create("Name", "desc"));
  *   List<LabelValue> labelValues = Arrays.asList(LabelValue.create("Inbound"));
  *
- *   // TODO(mayurkale): Plugs-in the DoubleGauge into the registry.
  *   DoubleGauge gauge = metricRegistry.addDoubleGauge("queue_size",
  *                       "Pending jobs", "1", labelKeys);
  *
@@ -86,7 +85,7 @@ public abstract class DoubleGauge {
    * method for manual operations.
    *
    * @param labelValues the list of label values. The number of label values must be the same to
-   *     that of the label keys.
+   *     that of the label keys passed to {@link MetricRegistry#addDoubleGauge}.
    * @return a {@code DoublePoint} the value of single gauge.
    * @throws NullPointerException if {@code labelValues} is null OR any element of {@code
    *     labelValues} is null.
diff --git a/api/src/main/java/io/opencensus/metrics/MetricRegistry.java b/api/src/main/java/io/opencensus/metrics/MetricRegistry.java
index 840ad787..557f886a 100644
--- a/api/src/main/java/io/opencensus/metrics/MetricRegistry.java
+++ b/api/src/main/java/io/opencensus/metrics/MetricRegistry.java
@@ -46,6 +46,23 @@ public abstract class MetricRegistry {
   public abstract LongGauge addLongGauge(
       String name, String description, String unit, List<LabelKey> labelKeys);
 
+  /**
+   * Builds a new double gauge to be added to the registry. This is more convenient form when you
+   * want to manually increase and decrease values as per your service requirements.
+   *
+   * @param name the name of the metric.
+   * @param description the description of the metric.
+   * @param unit the unit of the metric.
+   * @param labelKeys the list of the label keys.
+   * @throws NullPointerException if {@code labelKeys} is null OR any element of {@code labelKeys}
+   *     is null OR {@code name}, {@code description}, {@code unit} is null.
+   * @throws IllegalArgumentException if different metric with the same name already registered.
+   * @since 0.17
+   */
+  @ExperimentalApi
+  public abstract DoubleGauge addDoubleGauge(
+      String name, String description, String unit, List<LabelKey> labelKeys);
+
   static MetricRegistry newNoopMetricRegistry() {
     return new NoopMetricRegistry();
   }
@@ -63,5 +80,17 @@ public abstract class MetricRegistry {
           Utils.checkNotNull(unit, "unit"),
           labelKeys);
     }
+
+    @Override
+    public DoubleGauge addDoubleGauge(
+        String name, String description, String unit, List<LabelKey> labelKeys) {
+      Utils.checkListElementNotNull(
+          Utils.checkNotNull(labelKeys, "labelKeys"), "labelKey element should not be null.");
+      return DoubleGauge.newNoopDoubleGauge(
+          Utils.checkNotNull(name, "name"),
+          Utils.checkNotNull(description, "description"),
+          Utils.checkNotNull(unit, "unit"),
+          labelKeys);
+    }
   }
 }
diff --git a/api/src/test/java/io/opencensus/metrics/MetricRegistryTest.java b/api/src/test/java/io/opencensus/metrics/MetricRegistryTest.java
index 0d90fa97..2de04096 100644
--- a/api/src/test/java/io/opencensus/metrics/MetricRegistryTest.java
+++ b/api/src/test/java/io/opencensus/metrics/MetricRegistryTest.java
@@ -32,6 +32,7 @@ public class MetricRegistryTest {
   @Rule public ExpectedException thrown = ExpectedException.none();
 
   private static final String NAME = "name";
+  private static final String NAME_2 = "name2";
   private static final String DESCRIPTION = "description";
   private static final String UNIT = "1";
   private static final List<LabelKey> LABEL_KEY =
@@ -78,17 +79,60 @@ public class MetricRegistryTest {
   }
 
   @Test
+  public void noopAddDoubleGauge_NullName() {
+    thrown.expect(NullPointerException.class);
+    thrown.expectMessage("name");
+    metricRegistry.addDoubleGauge(null, DESCRIPTION, UNIT, LABEL_KEY);
+  }
+
+  @Test
+  public void noopAddDoubleGauge_NullDescription() {
+    thrown.expect(NullPointerException.class);
+    thrown.expectMessage("description");
+    metricRegistry.addDoubleGauge(NAME_2, null, UNIT, LABEL_KEY);
+  }
+
+  @Test
+  public void noopAddDoubleGauge_NullUnit() {
+    thrown.expect(NullPointerException.class);
+    thrown.expectMessage("unit");
+    metricRegistry.addDoubleGauge(NAME_2, DESCRIPTION, null, LABEL_KEY);
+  }
+
+  @Test
+  public void noopAddDoubleGauge_NullLabels() {
+    thrown.expect(NullPointerException.class);
+    thrown.expectMessage("labelKeys");
+    metricRegistry.addDoubleGauge(NAME_2, DESCRIPTION, UNIT, null);
+  }
+
+  @Test
+  public void noopAddDoubleGauge_WithNullElement() {
+    List<LabelKey> labelKeys = Collections.singletonList(null);
+    thrown.expect(NullPointerException.class);
+    thrown.expectMessage("labelKey element should not be null.");
+    metricRegistry.addDoubleGauge(NAME_2, DESCRIPTION, UNIT, labelKeys);
+  }
+
+  @Test
   public void noopSameAs() {
     LongGauge longGauge = metricRegistry.addLongGauge(NAME, DESCRIPTION, UNIT, LABEL_KEY);
     assertThat(longGauge.getDefaultTimeSeries()).isSameAs(longGauge.getDefaultTimeSeries());
     assertThat(longGauge.getDefaultTimeSeries())
         .isSameAs(longGauge.getOrCreateTimeSeries(LABEL_VALUES));
+
+    DoubleGauge doubleGauge = metricRegistry.addDoubleGauge(NAME_2, DESCRIPTION, UNIT, LABEL_KEY);
+    assertThat(doubleGauge.getDefaultTimeSeries()).isSameAs(doubleGauge.getDefaultTimeSeries());
+    assertThat(doubleGauge.getDefaultTimeSeries())
+        .isSameAs(doubleGauge.getOrCreateTimeSeries(LABEL_VALUES));
   }
 
   @Test
   public void noopInstanceOf() {
-    LongGauge longGauge = metricRegistry.addLongGauge(NAME, DESCRIPTION, UNIT, LABEL_KEY);
-    assertThat(longGauge)
+    assertThat(metricRegistry.addLongGauge(NAME, DESCRIPTION, UNIT, LABEL_KEY))
         .isInstanceOf(LongGauge.newNoopLongGauge(NAME, DESCRIPTION, UNIT, LABEL_KEY).getClass());
+    assertThat(metricRegistry.addDoubleGauge(NAME_2, DESCRIPTION, UNIT, LABEL_KEY))
+        .isInstanceOf(
+            DoubleGauge.newNoopDoubleGauge(NAME_2, DESCRIPTION, UNIT, LABEL_KEY).getClass());
   }
 }