io.opencensus.metrics

Class DerivedDoubleGauge

java.lang.Object

io.opencensus.metrics.DerivedDoubleGauge

@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 Summary

Constructors

Constructor and Description
DerivedDoubleGauge()

Method Summary

Modifier and Type	Method and Description
abstract void	clear() Removes all TimeSeries from the gauge metric.
abstract <T> void	createTimeSeries(List<LabelValue> labelValues, T obj, ToDoubleFunction<T> function) Creates a TimeSeries.
abstract void	removeTimeSeries(List<LabelValue> labelValues) Removes the TimeSeries from the gauge metric, if it is present.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DerivedDoubleGauge

public DerivedDoubleGauge()

Method Detail

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