WebFlux auto-configuration should only configure the blocking executor when virtual threads are enabled

[konnik]

Description of the problem

Incoming http-requests during graceful shutdown throws exceptions and 500 responses to the client.
Expected behavior is "connection refused" or 503 with no exceptions logged.

I'm using:

• Spring Boot 3.2.2
• Spring Webflux
• Kotlin

Example program

The application is configured with:

server.shutdown=graceful
management.endpoint.health.probes.enabled=true
management.health.livenessState.enabled=true
management.health.readinessState.enabled=true

Application code:

@SpringBootApplication
class GracefulShutdownLabbApplication

fun main(args: Array<String>) {
    runApplication<GracefulShutdownLabbApplication>(*args)
}


@RestController
class MyController {

    @GetMapping("/hello")
    suspend fun hello(): String {
        println("Enter /hello")
        delay(1.seconds)
        println("Leave /hello")
        return "Hello my friend, the current time is " + LocalTime.now()
    }
}

/**
 * Simulate a component with a slow shutdown.
 */
@Component
class MySlowComponent(private var running: Boolean = false) : SmartLifecycle {
    override fun start() {
        running = true
    }

    override fun stop() {
        println("5 seconds delay before stopping MySlowComponent..")
        Thread.sleep(5000)
        println("Stopping MySlowComponent!")
        running = false
    }

    override fun isRunning(): Boolean {
        return running
    }
}

Reproduce

1. Start application
2. Generate traffic watch -n 0.5 curl -s -v http://localhost:8080/hello
3. Stop application with SIGINT

The application responds with 500 internal server errors and logs exceptions.

Logs:

2024-02-08T14:59:59.361+01:00  INFO 3484426 --- [  restartedMain] n.g.GracefulShutdownLabbApplicationKt    : Starting GracefulShutdownLabbApplicationKt using Java 21 with PID 3484426 (/home/nikkon/devel/graceful-shutdown-labb/build/classes/kotlin/main started by nikkon in /home/nikkon/devel/graceful-shutdown-labb)
2024-02-08T14:59:59.363+01:00  INFO 3484426 --- [  restartedMain] n.g.GracefulShutdownLabbApplicationKt    : No active profile set, falling back to 1 default profile: "default"
2024-02-08T14:59:59.397+01:00  INFO 3484426 --- [  restartedMain] .e.DevToolsPropertyDefaultsPostProcessor : Devtools property defaults active! Set 'spring.devtools.add-properties' to 'false' to disable
2024-02-08T14:59:59.397+01:00  INFO 3484426 --- [  restartedMain] .e.DevToolsPropertyDefaultsPostProcessor : For additional web related logging consider setting the 'logging.level.web' property to 'DEBUG'
2024-02-08T15:00:00.216+01:00  INFO 3484426 --- [  restartedMain] o.s.b.a.e.web.EndpointLinksResolver      : Exposing 1 endpoint(s) beneath base path '/actuator'
2024-02-08T15:00:00.375+01:00  INFO 3484426 --- [  restartedMain] o.s.b.d.a.OptionalLiveReloadServer       : LiveReload server is running on port 35729
2024-02-08T15:00:00.445+01:00  INFO 3484426 --- [  restartedMain] o.s.b.web.embedded.netty.NettyWebServer  : Netty started on port 8080
2024-02-08T15:00:00.452+01:00  INFO 3484426 --- [  restartedMain] n.g.GracefulShutdownLabbApplicationKt    : Started GracefulShutdownLabbApplicationKt in 1.292 seconds (process running for 1.621)
Enter /hello
Leave /hello
Enter /hello
Leave /hello
Enter /hello
Leave /hello
Enter /hello
Leave /hello
Enter /hello
Leave /hello
Enter /hello
Leave /hello
5 seconds delay before stopping MySlowComponent..
Exception in thread "reactor-http-epoll-2" org.springframework.core.task.TaskRejectedException: ExecutorService in shutdown state did not accept task: false
	at org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor.execute(ThreadPoolTaskExecutor.java:365)
	at reactor.core.scheduler.ExecutorScheduler$ExecutorSchedulerWorker.schedule(ExecutorScheduler.java:252)
	at reactor.core.publisher.MonoSubscribeOn.subscribeOrReturn(MonoSubscribeOn.java:55)
	at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:63)
	at reactor.core.publisher.MonoFlatMap$FlatMapMain.onNext(MonoFlatMap.java:165)
	at reactor.core.publisher.FluxOnErrorResume$ResumeSubscriber.onNext(FluxOnErrorResume.java:79)
	at reactor.core.publisher.FluxSwitchIfEmpty$SwitchIfEmptySubscriber.onNext(FluxSwitchIfEmpty.java:74)
	at reactor.core.publisher.MonoNext$NextSubscriber.onNext(MonoNext.java:82)
	at reactor.core.publisher.FluxConcatMapNoPrefetch$FluxConcatMapNoPrefetchSubscriber.innerNext(FluxConcatMapNoPrefetch.java:259)
	at reactor.core.publisher.FluxConcatMap$ConcatMapInner.onNext(FluxConcatMap.java:865)
	at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java:129)
	at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.onNext(MonoPeekTerminal.java:180)
	at reactor.core.publisher.Operators$ScalarSubscription.request(Operators.java:2571)
	at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.request(MonoPeekTerminal.java:139)
	at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.request(FluxMapFuseable.java:171)
	at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.request(Operators.java:2331)
	at reactor.core.publisher.FluxConcatMapNoPrefetch$FluxConcatMapNoPrefetchSubscriber.request(FluxConcatMapNoPrefetch.java:339)
	at reactor.core.publisher.MonoNext$NextSubscriber.request(MonoNext.java:108)
	at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.set(Operators.java:2367)
	at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.onSubscribe(Operators.java:2241)
	at reactor.core.publisher.MonoNext$NextSubscriber.onSubscribe(MonoNext.java:70)
	at reactor.core.publisher.FluxConcatMapNoPrefetch$FluxConcatMapNoPrefetchSubscriber.onSubscribe(FluxConcatMapNoPrefetch.java:164)
	at reactor.core.publisher.FluxIterable.subscribe(FluxIterable.java:201)
	at reactor.core.publisher.FluxIterable.subscribe(FluxIterable.java:83)
	at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:76)
	at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:53)
	at reactor.core.publisher.Mono.subscribe(Mono.java:4512)
	at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.subscribeNext(MonoIgnoreThen.java:265)
	at reactor.core.publisher.MonoIgnoreThen.subscribe(MonoIgnoreThen.java:51)
	at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:76)
	at reactor.core.publisher.MonoDeferContextual.subscribe(MonoDeferContextual.java:55)
	at reactor.netty.http.server.HttpServer$HttpServerHandle.onStateChange(HttpServer.java:1169)
	at reactor.netty.ReactorNetty$CompositeConnectionObserver.onStateChange(ReactorNetty.java:710)
	at reactor.netty.transport.ServerTransport$ChildObserver.onStateChange(ServerTransport.java:481)
	at reactor.netty.http.server.HttpServerOperations.onInboundNext(HttpServerOperations.java:652)
	at reactor.netty.channel.ChannelOperationsHandler.channelRead(ChannelOperationsHandler.java:114)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:444)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
	at reactor.netty.http.server.HttpTrafficHandler.channelRead(HttpTrafficHandler.java:238)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:442)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
	at io.netty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.fireChannelRead(CombinedChannelDuplexHandler.java:436)
	at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:346)
	at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:318)
	at io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:251)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:442)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
	at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:440)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
	at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919)
	at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:800)
	at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:509)
	at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:407)
	at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997)
	at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
	at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
	at java.base/java.lang.Thread.run(Thread.java:1583)
Caused by: java.util.concurrent.RejectedExecutionException: Task false rejected from org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor$1@354c4a7d[Terminated, pool size = 0, active threads = 0, queued tasks = 0, completed tasks = 6]
	at java.base/java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:2081)
	at java.base/java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:841)
	at java.base/java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1376)
	at org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor$1.execute(ThreadPoolTaskExecutor.java:269)
	at org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor.execute(ThreadPoolTaskExecutor.java:362)
	... 60 more
2024-02-08T15:00:09.761+01:00 ERROR 3484426 --- [or-http-epoll-2] a.w.r.e.AbstractErrorWebExceptionHandler : [2e34d503-49]  500 Server Error for HTTP GET "/hello"

reactor.core.Exceptions$ReactorRejectedExecutionException: Scheduler unavailable
	at reactor.core.Exceptions.failWithRejected(Exceptions.java:283) ~[reactor-core-3.6.2.jar:3.6.2]
	Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException: 
Error has been observed at the following site(s):
	*__checkpoint ⇢ HTTP GET "/hello" [ExceptionHandlingWebHandler]
Original Stack Trace:
		at reactor.core.Exceptions.failWithRejected(Exceptions.java:283) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.scheduler.ExecutorScheduler$ExecutorSchedulerWorker.schedule(ExecutorScheduler.java:257) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.MonoSubscribeOn.subscribeOrReturn(MonoSubscribeOn.java:55) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:63) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.MonoFlatMap$FlatMapMain.onNext(MonoFlatMap.java:165) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.FluxOnErrorResume$ResumeSubscriber.onNext(FluxOnErrorResume.java:79) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.FluxSwitchIfEmpty$SwitchIfEmptySubscriber.onNext(FluxSwitchIfEmpty.java:74) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.MonoNext$NextSubscriber.onNext(MonoNext.java:82) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.FluxConcatMapNoPrefetch$FluxConcatMapNoPrefetchSubscriber.innerNext(FluxConcatMapNoPrefetch.java:259) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.FluxConcatMap$ConcatMapInner.onNext(FluxConcatMap.java:865) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java:129) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.onNext(MonoPeekTerminal.java:180) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.Operators$ScalarSubscription.request(Operators.java:2571) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.request(MonoPeekTerminal.java:139) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.request(FluxMapFuseable.java:171) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.request(Operators.java:2331) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.FluxConcatMapNoPrefetch$FluxConcatMapNoPrefetchSubscriber.request(FluxConcatMapNoPrefetch.java:339) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.MonoNext$NextSubscriber.request(MonoNext.java:108) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.set(Operators.java:2367) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.onSubscribe(Operators.java:2241) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.MonoNext$NextSubscriber.onSubscribe(MonoNext.java:70) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.FluxConcatMapNoPrefetch$FluxConcatMapNoPrefetchSubscriber.onSubscribe(FluxConcatMapNoPrefetch.java:164) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.FluxIterable.subscribe(FluxIterable.java:201) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.FluxIterable.subscribe(FluxIterable.java:83) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:76) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:53) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.Mono.subscribe(Mono.java:4512) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.subscribeNext(MonoIgnoreThen.java:265) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.MonoIgnoreThen.subscribe(MonoIgnoreThen.java:51) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:76) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.core.publisher.MonoDeferContextual.subscribe(MonoDeferContextual.java:55) ~[reactor-core-3.6.2.jar:3.6.2]
		at reactor.netty.http.server.HttpServer$HttpServerHandle.onStateChange(HttpServer.java:1169) ~[reactor-netty-http-1.1.15.jar:1.1.15]
		at reactor.netty.ReactorNetty$CompositeConnectionObserver.onStateChange(ReactorNetty.java:710) ~[reactor-netty-core-1.1.15.jar:1.1.15]
		at reactor.netty.transport.ServerTransport$ChildObserver.onStateChange(ServerTransport.java:481) ~[reactor-netty-core-1.1.15.jar:1.1.15]
		at reactor.netty.http.server.HttpServerOperations.onInboundNext(HttpServerOperations.java:652) ~[reactor-netty-http-1.1.15.jar:1.1.15]
		at reactor.netty.channel.ChannelOperationsHandler.channelRead(ChannelOperationsHandler.java:114) ~[reactor-netty-core-1.1.15.jar:1.1.15]
		at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:444) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
		at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
		at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
		at reactor.netty.http.server.HttpTrafficHandler.channelRead(HttpTrafficHandler.java:238) ~[reactor-netty-http-1.1.15.jar:1.1.15]
		at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:442) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
		at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
		at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
		at io.netty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.fireChannelRead(CombinedChannelDuplexHandler.java:436) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
		at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:346) ~[netty-codec-4.1.105.Final.jar:4.1.105.Final]
		at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:318) ~[netty-codec-4.1.105.Final.jar:4.1.105.Final]
		at io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:251) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
		at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:442) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
		at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
		at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
		at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
		at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:440) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
		at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
		at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
		at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:800) ~[netty-transport-classes-epoll-4.1.105.Final.jar:4.1.105.Final]
		at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:509) ~[netty-transport-classes-epoll-4.1.105.Final.jar:4.1.105.Final]
		at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:407) ~[netty-transport-classes-epoll-4.1.105.Final.jar:4.1.105.Final]
		at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997) ~[netty-common-4.1.105.Final.jar:4.1.105.Final]
		at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[netty-common-4.1.105.Final.jar:4.1.105.Final]
		at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) ~[netty-common-4.1.105.Final.jar:4.1.105.Final]
		at java.base/java.lang.Thread.run(Thread.java:1583) ~[na:na]
Caused by: org.springframework.core.task.TaskRejectedException: ExecutorService in shutdown state did not accept task: false
	at org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor.execute(ThreadPoolTaskExecutor.java:365) ~[spring-context-6.1.3.jar:6.1.3]
	at reactor.core.scheduler.ExecutorScheduler$ExecutorSchedulerWorker.schedule(ExecutorScheduler.java:252) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.MonoSubscribeOn.subscribeOrReturn(MonoSubscribeOn.java:55) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:63) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.MonoFlatMap$FlatMapMain.onNext(MonoFlatMap.java:165) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.FluxOnErrorResume$ResumeSubscriber.onNext(FluxOnErrorResume.java:79) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.FluxSwitchIfEmpty$SwitchIfEmptySubscriber.onNext(FluxSwitchIfEmpty.java:74) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.MonoNext$NextSubscriber.onNext(MonoNext.java:82) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.FluxConcatMapNoPrefetch$FluxConcatMapNoPrefetchSubscriber.innerNext(FluxConcatMapNoPrefetch.java:259) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.FluxConcatMap$ConcatMapInner.onNext(FluxConcatMap.java:865) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java:129) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.onNext(MonoPeekTerminal.java:180) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.Operators$ScalarSubscription.request(Operators.java:2571) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.request(MonoPeekTerminal.java:139) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.request(FluxMapFuseable.java:171) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.request(Operators.java:2331) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.FluxConcatMapNoPrefetch$FluxConcatMapNoPrefetchSubscriber.request(FluxConcatMapNoPrefetch.java:339) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.MonoNext$NextSubscriber.request(MonoNext.java:108) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.set(Operators.java:2367) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.onSubscribe(Operators.java:2241) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.MonoNext$NextSubscriber.onSubscribe(MonoNext.java:70) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.FluxConcatMapNoPrefetch$FluxConcatMapNoPrefetchSubscriber.onSubscribe(FluxConcatMapNoPrefetch.java:164) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.FluxIterable.subscribe(FluxIterable.java:201) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.FluxIterable.subscribe(FluxIterable.java:83) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:76) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:53) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.Mono.subscribe(Mono.java:4512) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.subscribeNext(MonoIgnoreThen.java:265) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.MonoIgnoreThen.subscribe(MonoIgnoreThen.java:51) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:76) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.core.publisher.MonoDeferContextual.subscribe(MonoDeferContextual.java:55) ~[reactor-core-3.6.2.jar:3.6.2]
	at reactor.netty.http.server.HttpServer$HttpServerHandle.onStateChange(HttpServer.java:1169) ~[reactor-netty-http-1.1.15.jar:1.1.15]
	at reactor.netty.ReactorNetty$CompositeConnectionObserver.onStateChange(ReactorNetty.java:710) ~[reactor-netty-core-1.1.15.jar:1.1.15]
	at reactor.netty.transport.ServerTransport$ChildObserver.onStateChange(ServerTransport.java:481) ~[reactor-netty-core-1.1.15.jar:1.1.15]
	at reactor.netty.http.server.HttpServerOperations.onInboundNext(HttpServerOperations.java:652) ~[reactor-netty-http-1.1.15.jar:1.1.15]
	at reactor.netty.channel.ChannelOperationsHandler.channelRead(ChannelOperationsHandler.java:114) ~[reactor-netty-core-1.1.15.jar:1.1.15]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:444) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
	at reactor.netty.http.server.HttpTrafficHandler.channelRead(HttpTrafficHandler.java:238) ~[reactor-netty-http-1.1.15.jar:1.1.15]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:442) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
	at io.netty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.fireChannelRead(CombinedChannelDuplexHandler.java:436) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
	at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:346) ~[netty-codec-4.1.105.Final.jar:4.1.105.Final]
	at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:318) ~[netty-codec-4.1.105.Final.jar:4.1.105.Final]
	at io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:251) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:442) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
	at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:440) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
	at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919) ~[netty-transport-4.1.105.Final.jar:4.1.105.Final]
	at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:800) ~[netty-transport-classes-epoll-4.1.105.Final.jar:4.1.105.Final]
	at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:509) ~[netty-transport-classes-epoll-4.1.105.Final.jar:4.1.105.Final]
	at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:407) ~[netty-transport-classes-epoll-4.1.105.Final.jar:4.1.105.Final]
	at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997) ~[netty-common-4.1.105.Final.jar:4.1.105.Final]
	at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[netty-common-4.1.105.Final.jar:4.1.105.Final]
	at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) ~[netty-common-4.1.105.Final.jar:4.1.105.Final]
	at java.base/java.lang.Thread.run(Thread.java:1583) ~[na:na]
Caused by: java.util.concurrent.RejectedExecutionException: Task false rejected from org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor$1@354c4a7d[Terminated, pool size = 0, active threads = 0, queued tasks = 0, completed tasks = 6]
	at java.base/java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:2081) ~[na:na]
	at java.base/java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:841) ~[na:na]
	at java.base/java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1376) ~[na:na]
	at org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor$1.execute(ThreadPoolTaskExecutor.java:269) ~[spring-context-6.1.3.jar:6.1.3]
	at org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor.execute(ThreadPoolTaskExecutor.java:362) ~[spring-context-6.1.3.jar:6.1.3]
	... 60 common frames omitted

<repeated errors removed> 

Stopping MySlowComponent!
2024-02-08T15:00:14.265+01:00  INFO 3484426 --- [ionShutdownHook] o.s.b.w.embedded.netty.GracefulShutdown  : Commencing graceful shutdown. Waiting for active requests to complete
2024-02-08T15:00:14.266+01:00  INFO 3484426 --- [ netty-shutdown] o.s.b.w.embedded.netty.GracefulShutdown  : Graceful shutdown complete

Process finished with exit code 130 (interrupted by signal 2:SIGINT)

[wilkinsona]

It appears that ThreadPoolTaskExecutor$1@354c4a7d has been stopped before graceful shutdown has begun. I think this is due to this change in Spring Framework where the executor will start rejecting tasks when it receives the ContextClosedEvent. This event is published before graceful shutdown begins so the executor is stopped before requests will be rejected. Even without graceful shutdown, there is still a window where this problem could occur as the executor will be stopped before the HTTP connector is stopped. We'll discuss it with the Framework team.

[wilkinsona]

There are a few things going on here that are contributing to the problem:

1. Framework is rejecting tasks as soon as the context has been closed (ThreadPoolTaskExecutor rejecting tasks as soon as the context has been closed can lead to exceptions during web app shutdown spring-framework#32226)
2. Framework is treating your coroutine as blocking so it's unnecessarily being dispatched onto a separate thread (Add Coroutines support to NonReactiveHandlerMethodPredicate spring-framework#32227)
3. Boot is configuring Framework to use the application's task executor for blocking operations in all cases when the intent was that this would only happen when virtual threads are enabled

Any one of these should fix the problem. We'll use this issue to address 3.