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

package org.apache.juneau.rest.server.observation
Explicit programmatic observation API for juneau-rest-server — custom (non-request) metrics + tracing around an arbitrary block of work.
Why explicit (no @Observed annotation)

Juneau has no method-interception / AOP substrate (no dynamic proxying of arbitrary beans, no bytecode weaving, no annotation-processor agent). Rather than introduce one to support an @Observed-style annotation, custom observations are explicit: application code wraps a block in a try-with-resources over Observations#observe(String, String). This is consistent with the framework's explicit-over-magic philosophy — the same reason the curated dependency bundles register nothing automatically.

Reuses the request-path SPIs

Observations are recorded through the very same two SPIs the request path uses — MetricsRecorder (via its non-request record(name, tags, elapsed, error) default method) and TracerHook (via its non-request startSpan(name) default method) — and the same comma-separated metricName / metricTags model. The shipped bridges (MicrometerMetricsRecorder, OtelTracerHook) override those default methods; bridges that do not simply skip custom observations.

No-backend contract

When no backend is installed, Observations#observe(String, String) returns Observation#NOOP — no timestamp taken, no span opened, zero allocation beyond the try-with-resources scaffolding.

Since:
10.0.0