Andrea Cosentino created CAMEL-25804:
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Summary: camel-pqc - the Micrometer stateful key gauge is held
weakly and stops reporting
Key: CAMEL-25804
URL: https://issues.apache.org/jira/browse/CAMEL-25804
Project: Camel
Issue Type: Bug
Components: camel-pqc
Reporter: Andrea Cosentino
The {{camel.pqc.stateful.key.remaining}} gauge is registered against a lambda
that nothing keeps alive, so it reports {{NaN}} once that lambda is garbage
collected.
{{PQCMicrometerMetrics.java:71-78}}:
{code:java}
@Override
public void registerStatefulKeyGauge(String algorithm, LongSupplier
remainingSupplier) {
statefulKeyGauge = Gauge.builder(METRIC_STATEFUL_REMAINING,
remainingSupplier, LongSupplier::getAsLong)
.tag("algorithm", algorithm)
.description("Remaining signatures for the stateful PQC
signature key")
.register(registry);
}
{code}
Micrometer's {{Gauge.builder(String, T obj, ToDoubleFunction<T>)}} holds the
state object *weakly*. Verified against the {{micrometer-core}} jar on disk:
{noformat}
public class io.micrometer.core.instrument.internal.DefaultGauge<T> ... {
private final java.lang.ref.WeakReference<T> ref;
{noformat}
The only reference to the supplier is the inline lambda passed by the producer
— {{PQCProducer.java:504-509}}:
{code:java}
metrics.registerStatefulKeyGauge(signatureAlgorithm, () -> {
KeyPair kp = getRuntimeKeyPair();
return kp != null && kp.getPrivate() != null ?
getStatefulKeyRemaining(kp.getPrivate()) : -1;
});
{code}
Neither the producer nor {{PQCMicrometerMetrics}} stores it — the class keeps
only the {{Gauge}}. So after the next GC the metric that tells an operator a
one-time-use key is approaching exhaustion goes dark, silently.
h3. Two related issues in the same class
{{statefulKeyGauge}} is a single field ({{:40}}), so a second
{{registerStatefulKeyGauge}} call leaks the first gauge rather than replacing
it cleanly.
{{close()}} ({{:80-87}}) removes meters by id from a shared {{MeterRegistry}},
so stopping one producer unregisters counters still in use by another producer
carrying the same {{operation|algorithm|outcome}} tags.
h3. Suggested fix
Keep a strong reference to the supplier in a field of {{PQCMicrometerMetrics}}
(a map keyed by algorithm, so multiple registrations work), and make
{{close()}} only remove meters this instance actually created.
h3. Test gap
No test asserts the gauge still reports a value after a GC, nor that two
producers sharing a registry do not unregister each other's counters.
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_Reported by Claude Code (AI agent) on behalf of [~oscerd]. Every code
reference was verified against commit {{7aae27315946}} on {{main}}._
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