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

2 files changed, 31 insertions, 3 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);
+    }
   }
 }