"Span wasn't started - an observation must be started (not only created)" (Micrometer) due to observation handling in Spring Security Web?

[janekbettinger]

Describe the bug
In all of our Spring WebFlux-based applications having integrated Spring Security Web and Micrometer, we sporadically see the following exception:

java.lang.IllegalStateException: Span wasn't started - an observation must be started (not only created)
        at io.micrometer.tracing.handler.TracingObservationHandler.getRequiredSpan(TracingObservationHandler.java:209) ~[micrometer-tracing-1.2.1.jar:1.2.1]
        Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException: 
Error has been observed at the following site(s):
        *__checkpoint ⇢ ServerWebExchangeReactorContextWebFilter [DefaultWebFilterChain]
        *__checkpoint ⇢ org.springframework.security.web.server.WebFilterChainProxy [DefaultWebFilterChain]
        *__checkpoint ⇢ HTTP GET "/actuator/health" [ExceptionHandlingWebHandler]
Original Stack Trace:
                at io.micrometer.tracing.handler.TracingObservationHandler.getRequiredSpan(TracingObservationHandler.java:209) ~[micrometer-tracing-1.2.1.jar:1.2.1]
                at io.micrometer.tracing.handler.DefaultTracingObservationHandler.onStop(DefaultTracingObservationHandler.java:50) ~[micrometer-tracing-1.2.1.jar:1.2.1]
                at io.micrometer.observation.ObservationHandler$FirstMatchingCompositeObservationHandler.onStop(ObservationHandler.java:197) ~[micrometer-observation-1.12.1.jar:1.12.1]
                at io.micrometer.observation.SimpleObservation.lambda$notifyOnObservationStopped$0(SimpleObservation.java:268) ~[micrometer-observation-1.12.1.jar:1.12.1]
                at java.base/java.util.ArrayDeque$DescendingIterator.forEachRemaining(ArrayDeque.java:771) ~[na:na]
                at io.micrometer.observation.SimpleObservation.notifyOnObservationStopped(SimpleObservation.java:268) ~[micrometer-observation-1.12.1.jar:1.12.1]
                at io.micrometer.observation.SimpleObservation.stop(SimpleObservation.java:188) ~[micrometer-observation-1.12.1.jar:1.12.1]
                at org.springframework.security.web.server.ObservationWebFilterChainDecorator$PhasedObservation.close(ObservationWebFilterChainDecorator.java:763) ~[spring-security-web-6.2.1.jar:6.2.1]
                at org.springframework.security.web.server.ObservationWebFilterChainDecorator$AroundWebFilterObservation$SimpleAroundWebFilterObservation.close(ObservationWebFilterChainDecorator.java:301) ~[spring-security-web-6.2.1.jar:6.2.1]
                at org.springframework.security.web.server.ObservationWebFilterChainDecorator$AroundWebFilterObservation$SimpleAroundWebFilterObservation.lambda$wrap$3(ObservationWebFilterChainDecorator.java:366) ~[spring-security-web-6.2.1.jar:6.2.1]
                at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.onComplete(MonoPeekTerminal.java:289) ~[reactor-core-3.6.1.jar:3.6.1]
                ...
                at reactor.core.publisher.FluxSubscribeOnCallable$CallableSubscribeOnSubscription.run(FluxSubscribeOnCallable.java:252) ~[reactor-core-3.6.1.jar:3.6.1]
                at io.micrometer.context.ContextSnapshot.lambda$wrap$0(ContextSnapshot.java:91) ~[context-propagation-1.1.0.jar:1.1.0]
                ...
                at java.base/java.lang.Thread.run(Thread.java:1583) ~[na:na]

(full stacktrace)

It mainly happens on /actuator/health calls, but not exclusively. E.g. with Spring Cloud Gateway we randomly see this exceptions on non-routable routes as well. Closed connections can provoke the behavior as well.

The issue might be caused by the Observation handling by Spring Security Web in o.s.security.web.server.ObservationWebFilterChainDecorator. Replacing start() with close() in the onSuccess handler of the WebFilterChain wrapper seems to prevent the failure.

Related issues

• IllegalStateException: Span wasn't started - an observation must be started (not only created) micrometer-metrics/tracing#357
• ObservationWebFilterChainDecorator cancel signal triggers Observation::start #13827

To Reproduce
Follow the README.md in the minimal, reproducible sample linked below.

Expected behavior
Only started observations should be stopped.

Sample
https://github.com/janekbettinger/micrometer-spring-security-sample

• spring-security-web:6.2.1
• spring-boot-starter-webflux:3.6.1
• io.micrometer:micrometer-observation:1.12.1
• Java 21 (same behavior with Java 17)

[Yocker95k]

We have the same issue which is really annoying since it spams our monitoring and alerting system in Prod.

• Spring Boot: 3.1.6
• Webflux: 6.0.14
• Security: 6.15
• Micrometer: 1.11.6

[janekbettinger]

@jzheaux might be able to support here. Thanks in advance!

[jzheaux]

Thanks, @janekbettinger, for the reproducer. Please try with the latest fix, which is available in the 6.1.7-SNAPSHOT, 6.2.2-SNAPSHOT, and 6.3.0-SNAPSHOT releases.

[janekbettinger]

Thanks for the fix, @jzheaux, it looks very reasonable! With the sample application and 6.2.2-SNAPSHOT I can no longer reproduce the bug. I'll let you know if we ever see it in our production apps.

[sfotedar995]

Hi @jzheaux ,

We were facing the issue:
IllegalStateException: Span wasn't started - an observation must be started (not only created)

Currently, the spring boot version we are using is 3.1.2.

Could you confirm in which version of spring boot this issue is fixed along with its micrometer version?