io.opentelemetry.metrics

Interface DoubleValueObserver

All Superinterfaces:

AsynchronousInstrument<DoubleValueObserver.ResultDoubleValueObserver>, Instrument

@ThreadSafe
public interface DoubleValueObserver
extends AsynchronousInstrument<DoubleValueObserver.ResultDoubleValueObserver>

ValueObserver is the asynchronous instrument corresponding to ValueRecorder, used to capture values that are treated as individual observations, recorded with the observe(value) method.

A ValueObserver is a good choice in situations where a measurement is expensive to compute, such that it would be wasteful to compute on every request.

Example:

 class YourClass {

   private static final Meter meter = OpenTelemetry.getMeterRegistry().get("my_library_name");
   private static final DoubleValueObserver cpuObserver =
       meter.
           .doubleValueObserverBuilder("cpu_temperature")
           .setDescription("System CPU temperature")
           .setUnit("ms")
           .build();

   void init() {
     cpuObserver.setCallback(
         new DoubleValueObserver.Callback<ResultDoubleValueObserver>() {
          {@literal @}Override
           public void update(ResultDoubleValueObserver result) {
             // Get system cpu temperature
             result.observe(cpuTemperature);
           }
         });
   }
 }
 

Since:

0.5.0

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	DoubleValueObserver.Builder Builder class for DoubleValueObserver.
static interface	DoubleValueObserver.ResultDoubleValueObserver The result for the Callback.

Nested classes/interfaces inherited from interface io.opentelemetry.metrics.AsynchronousInstrument

AsynchronousInstrument.Callback<R>

Method Summary

Modifier and Type	Method and Description
void	setCallback(AsynchronousInstrument.Callback<DoubleValueObserver.ResultDoubleValueObserver> callback) Sets a callback that gets executed every collection interval.

Method Detail

setCallback

void setCallback(AsynchronousInstrument.Callback<DoubleValueObserver.ResultDoubleValueObserver> callback)

Description copied from interface: AsynchronousInstrument

Sets a callback that gets executed every collection interval.

Evaluation is deferred until needed, if this AsynchronousInstrument metric is not exported then it will never be called.

Specified by:

setCallback in interface AsynchronousInstrument<DoubleValueObserver.ResultDoubleValueObserver>

Parameters:

callback - the callback to be executed before export.