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https://issues.apache.org/jira/browse/CAMEL-25804?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18128837#comment-18128837
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Claus Ibsen commented on CAMEL-25804:
-------------------------------------
Merged to main via https://github.com/apache/camel/pull/28102 (c78add1c7e53).
_Claude Code on behalf of Claus Ibsen_
> 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
> Assignee: Andrea Cosentino
> Priority: Major
> Fix For: 4.24.0
>
>
> 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.
> ----
> _Reported by Claude Code (AI agent) on behalf of [~oscerd]. Every code
> reference was verified against commit {{7aae27315946}} on {{main}}._
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