Class DerivedDoubleGauge

java.lang.Object
io.opencensus.metrics.DerivedDoubleGauge
Direct Known Subclasses:
DerivedDoubleGauge.NoopDerivedDoubleGauge, DerivedDoubleGaugeImpl
@ThreadSafe public abstract class DerivedDoubleGauge extends Object
Derived Double Gauge metric, to report instantaneous measurement of a double value. Gauges can go both up and down. The gauges values can be negative.

Example: Create a Gauge with an object and a callback function. 

class YourClass {

  private static final MetricRegistry metricRegistry = Metrics.getMetricRegistry();

  List<LabelKey> labelKeys = Arrays.asList(LabelKey.create("Name", "desc"));
  List<LabelValue> labelValues = Arrays.asList(LabelValue.create("Inbound"));

  DerivedDoubleGauge gauge = metricRegistry.addDerivedDoubleGauge(
      "queue_size", "Pending jobs in a queue", "1", labelKeys);

  QueueManager queueManager = new QueueManager();
  gauge.createTimeSeries(labelValues, queueManager,
        new ToDoubleFunction<QueueManager>() {
          {@literal @}Override
          public double applyAsDouble(QueueManager queue) {
            return queue.size();
          }
        });

  void doWork() {
     // Your code here.
  }
}
Since:
0.17

  • Constructor Details

    • DerivedDoubleGauge

      public DerivedDoubleGauge()

  • Method Details

    • createTimeSeries

      public abstract <T> void createTimeSeries(List<LabelValue> labelValues, T obj, ToDoubleFunction<T> function)
      Creates a TimeSeries. The value of a single point in the TimeSeries is observed from a callback function. This function is invoked whenever metrics are collected, meaning the reported value is up-to-date. It keeps a WeakReference to the object and it is the user's responsibility to manage the lifetime of the object.
      Type Parameters:
      T - the type of the object upon which the function derives a measurement.
      Parameters:
      labelValues - the list of label values.
      obj - the state object from which the function derives a measurement.
      function - the function to be called.
      Throws:
      NullPointerException - if labelValues is null OR any element of labelValues is null OR function is null.
      IllegalArgumentException - if different time series with the same labels already exists OR if number of labelValuess are not equal to the label keys.
      Since:
      0.17

    • removeTimeSeries

      public abstract void removeTimeSeries(List<LabelValue> labelValues)
      Removes the TimeSeries from the gauge metric, if it is present.
      Parameters:
      labelValues - the list of label values.
      Throws:
      NullPointerException - if labelValues is null.
      Since:
      0.17

    • clear

      public abstract void clear()
      Removes all TimeSeries from the gauge metric.
      Since:
      0.17

    • newNoopDerivedDoubleGauge

      static DerivedDoubleGauge newNoopDerivedDoubleGauge(String name, String description, String unit, List<LabelKey> labelKeys)
      Returns the no-op implementation of the DerivedDoubleGauge.
      Returns:
      the no-op implementation of the DerivedDoubleGauge.
      Since:
      0.17