Expected Behavior
No exceptions are thrown
Actual Behavior
An exception is thrown:
java.lang.ClassCastException: class reactor.core.publisher.FluxContextWriteRestoringThreadLocals$ContextWriteRestoringThreadLocalsSubscriber cannot be cast to class reactor.core.Fuseable$QueueSubscription (reactor.core.publisher.FluxContextWriteRestoringThreadLocals$ContextWriteRestoringThreadLocalsSubscriber and reactor.core.Fuseable$QueueSubscription are in unnamed module of loader 'app')
at reactor.core.publisher.FluxMapFuseable$MapFuseableConditionalSubscriber.onSubscribe(FluxMapFuseable.java:264)
at reactor.core.publisher.FluxContextWriteRestoringThreadLocals$ContextWriteRestoringThreadLocalsSubscriber.onSubscribe(FluxContextWriteRestoringThreadLocals.java:104)
at reactor.core.publisher.FluxContextWriteRestoringThreadLocals$ContextWriteRestoringThreadLocalsSubscriber.onSubscribe(FluxContextWriteRestoringThreadLocals.java:104)
at reactor.core.publisher.FluxHide$SuppressFuseableSubscriber.onSubscribe(FluxHide.java:122)
at reactor.core.publisher.FluxContextWriteRestoringThreadLocals$ContextWriteRestoringThreadLocalsSubscriber.onSubscribe(FluxContextWriteRestoringThreadLocals.java:104)
at reactor.core.publisher.FluxContextWriteRestoringThreadLocals$ContextWriteRestoringThreadLocalsSubscriber.onSubscribe(FluxContextWriteRestoringThreadLocals.java:104)
at reactor.core.publisher.FluxContextWriteRestoringThreadLocals$ContextWriteRestoringThreadLocalsSubscriber.onSubscribe(FluxContextWriteRestoringThreadLocals.java:104)
at reactor.core.publisher.FluxContextWriteRestoringThreadLocals$ContextWriteRestoringThreadLocalsSubscriber.onSubscribe(FluxContextWriteRestoringThreadLocals.java:104)
at reactor.core.publisher.FluxRefCount$RefCountInner.setRefCountMonitor(FluxRefCount.java:209)
at reactor.core.publisher.FluxRefCount.subscribe(FluxRefCount.java:85)
at reactor.core.publisher.FluxContextWriteRestoringThreadLocals.subscribe(FluxContextWriteRestoringThreadLocals.java:46)
at reactor.core.publisher.Mono.subscribe(Mono.java:4512)
at reactor.core.publisher.Mono.subscribeWith(Mono.java:4578)
at reactor.core.publisher.Mono.subscribe(Mono.java:4478)
at reactor.core.publisher.Mono.subscribe(Mono.java:4414)
at reactor.core.publisher.Mono.subscribe(Mono.java:4361)
at org.example.ReactorClassCastExceptionReproducerSample.runSample(ReactorClassCastExceptionReproducerSample.java:44)
at org.example.ReactorClassCastExceptionReproducerSample.main(ReactorClassCastExceptionReproducerSample.java:18)
Steps to Reproduce
Reproducer is here: https://github.com/kz-dt/reactor_class_cast_exception_reproducer
private <T> Function<? super Publisher<T>, ? extends Publisher<T>> tracingLift() {
return Operators.lift((a, b) -> b);
}
@Test
void reproCase() {
Hooks.onEachOperator("testTracingLift", tracingLift());
Hooks.enableAutomaticContextPropagation();
Sinks.Many<String> sink = Sinks.many().unicast().onBackpressureBuffer();
Flux<String> flux = sink
.asFlux()
.doOnRequest(v -> System.out.println("OnDoRequest " + v))
.doOnTerminate(() -> System.out.println("doOnTerminate"))
.doOnCancel(() -> System.out.println("doOnCancel"))
.publish()
.refCount();
Mono<List<String>> res = flux.map(s -> s + " mapped").collectList();
res.subscribe(v -> System.out.println("Received a list of mapped strings: " + v));
}Possible Solution
It looks like Operators.lift returns wrong subscriber type. Calling Hooks.onOperatorDebug(); "fixes" the issue since it adds another wrapper.
Your Environment
reactor-core 3.6.+
micrometer jar should be in classpath
The issue originally was discovered with SpringBoot 3.2+ and couchbase java client 3.4.11, the dependencies were the following:
org.springframework.boot:spring-boot-starter-webflux:3.2.0
org.springframework.boot:spring-boot-starter-data-couchbase-reactive:3.2.0
- Reactor version(s) used: 3.6.0 - 3.6.4
- Other relevant libraries versions (eg.
netty, ...): micrometer-tracing:1.2.1
- JVM version (
java -version):
openjdk version "11.0.20.1" 2023-08-24
OpenJDK Runtime Environment Temurin-11.0.20.1+1 (build 11.0.20.1+1)
OpenJDK 64-Bit Server VM Temurin-11.0.20.1+1 (build 11.0.20.1+1, mixed mode)
- OS and version (eg
uname -a): MINGW64_NT-10.0-22631 DT-3Q41FY3 3.4.7-25de8b84.x86_64 2023-08-28 21:32 UTC x86_64 Msys
Expected Behavior
No exceptions are thrown
Actual Behavior
An exception is thrown:
Steps to Reproduce
Reproducer is here: https://github.com/kz-dt/reactor_class_cast_exception_reproducer
Possible Solution
It looks like Operators.lift returns wrong subscriber type. Calling
Hooks.onOperatorDebug();"fixes" the issue since it adds another wrapper.Your Environment
reactor-core 3.6.+
micrometer jar should be in classpath
The issue originally was discovered with SpringBoot 3.2+ and couchbase java client 3.4.11, the dependencies were the following:
org.springframework.boot:spring-boot-starter-webflux:3.2.0
org.springframework.boot:spring-boot-starter-data-couchbase-reactive:3.2.0
netty, ...): micrometer-tracing:1.2.1java -version):openjdk version "11.0.20.1" 2023-08-24
OpenJDK Runtime Environment Temurin-11.0.20.1+1 (build 11.0.20.1+1)
OpenJDK 64-Bit Server VM Temurin-11.0.20.1+1 (build 11.0.20.1+1, mixed mode)
uname -a): MINGW64_NT-10.0-22631 DT-3Q41FY3 3.4.7-25de8b84.x86_64 2023-08-28 21:32 UTC x86_64 Msys