Package io.opencensus.metrics

Class DerivedDoubleGauge

  • Direct Known Subclasses:
    DerivedDoubleGauge.NoopDerivedDoubleGauge, DerivedDoubleGaugeImpl
    @ThreadSafe
public abstract class DerivedDoubleGauge
extends java.lang.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 Detail

      • DerivedDoubleGauge

        public DerivedDoubleGauge()

    • Method Detail

      • createTimeSeries

        public abstract <T> void createTimeSeries​(java.util.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:
        java.lang.NullPointerException - if labelValues is null OR any element of labelValues is null OR function is null.
        java.lang.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​(java.util.List<LabelValue> labelValues)
        Removes the TimeSeries from the gauge metric, if it is present.
        Parameters:
        labelValues - the list of label values.
        Throws:
        java.lang.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​(java.lang.String name,
                                                    java.lang.String description,
                                                    java.lang.String unit,
                                                    java.util.List<LabelKey> labelKeys)
        Returns the no-op implementation of the DerivedDoubleGauge.
        Returns:
        the no-op implementation of the DerivedDoubleGauge.
        Since:
        0.17