Package org.apache.juneau.rest.server.observation

Class Observer

java.lang.Object

org.apache.juneau.rest.server.observation.Observer

public final class Observer
extends Object

Factory for custom (non-request) Observations, composing a MetricsRecorder and a TracerHook.

This is the explicit programmatic observation substrate for juneau-rest-server: it reuses the exact same two SPIs the request path uses (MetricsRecorder, TracerHook) and the same metricName / metricTags comma-separated tag model, but is decoupled from RestRequest so application code can instrument an arbitrary block of work. Juneau deliberately has no method-interception / AOP substrate, so observation is explicit (a try-with-resources block) rather than annotation-driven — consistent with the framework's explicit-over-magic philosophy.

No-backend contract

An Observer built from the no-op SPIs (NOOP) never takes a timestamp and hands back Observation.NOOP, so an observation in an unconfigured process costs nothing beyond the try-with-resources scaffolding. start(String, String) short-circuits to the no-op handle whenever both backends are the no-op singletons.

Wiring

Typically obtained from a RestContext's bean store — register the same @Bean MetricsRecorder / @Bean TracerHook you already register for request-path observability, then build an Observer from them (or install one as the Observations default). Construct directly for tests:

Observer o = new Observer(new MicrometerMetricsRecorder(registry), new OtelTracerHook(otel));

See Also:

• Observations
• Observation
• MetricsRecorder
• TracerHook

Since:

10.0.0

Field Summary

Fields

Modifier and Type	Field	Description
static final Observer	NOOP	Observer backed by the no-op metrics recorder and tracer — produces only Observation.NOOP.

Constructor Summary

Constructors

Constructor	Description
Observer(MetricsRecorder recorder, TracerHook tracer)	Constructor.

Method Summary

Modifier and Type	Method	Description
boolean	isActive()	Returns whether this observer has at least one live backend (metrics or tracing).
Observation	start(String name, String tags)	Starts a new observation.

Methods inherited from class java.lang.Object

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

Field Details

NOOP

public static final Observer NOOP

Observer backed by the no-op metrics recorder and tracer — produces only Observation.NOOP.

Constructor Details

Observer

public Observer(MetricsRecorder recorder,
 TracerHook tracer)

Constructor.

Parameters:

recorder - The metrics recorder to time observations against. Must not be null; use NoOpMetricsRecorder.INSTANCE to disable metrics.

tracer - The tracer to open spans against. Must not be null; use NoOpTracerHook.INSTANCE to disable tracing.

Method Details

start

public Observation start(String name,
 String tags)

Starts a new observation.

When both backends are the no-op singletons this returns Observation.NOOP without taking a timestamp or opening a span. Otherwise it opens a span via TracerHook.startSpan(String) and captures a start timestamp; the paired timer sample is recorded on Observation.close().

Parameters:

name - The observation name — used as both the span name and the metric timer name. Must not be null or blank.

tags - Additional metric tags as comma-separated key=value pairs (e.g. "team=payments,region=us-east"), or null / empty for none.

Returns:

The started Observation. Never null.

isActive

public boolean isActive()

Returns whether this observer has at least one live backend (metrics or tracing).

Returns:

true if either the metrics recorder or the tracer is non-no-op.