messageBrokerTaskScheduler incorrect type

[lukas-krecan]

Affects: 5.1.5

If you use @EnableWebSocketMessageBroker and @EnableScheduling in the same application,
AbstractMessageBrokerConfiguration creates a ThreadPoolTaskScheduler here. This TaskScheduler gets used by the scheduling framework because it simply scans for an available TaskScheduler. This is itself weird, since scheduled tasks are executed under threads with MessageBroker- thread name.

The real trouble begins, if you use Shedlock which tries to wrap scheduling task executor in a proxy. It then fails with

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'stompWebSocketHandlerMapping' defined in class path resource [org/springframework/web/socket/config/annotation/DelegatingWebSocketMessageBrokerConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.web.servlet.HandlerMapping]: Factory method 'stompWebSocketHandlerMapping' threw exception; nested exception is java.lang.IllegalStateException: @Bean method AbstractMessageBrokerConfiguration.messageBrokerTaskScheduler called as bean reference for type [org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler] but overridden by non-compatible bean instance of type [com.sun.proxy.$Proxy71]. Overriding bean of same name declared in: class path resource [org/springframework/web/socket/config/annotation/DelegatingWebSocketMessageBrokerConfiguration.class]
	at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:627)
	at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:456)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1305)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1144)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:555)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515)
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:849)
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:877)
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:549)
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:142)
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:785)
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:407)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:322)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1278)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1266)
	at net.javacrumbs.shedlock.test.boot.Application.main(Application.java:36)
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.web.servlet.HandlerMapping]: Factory method 'stompWebSocketHandlerMapping' threw exception; nested exception is java.lang.IllegalStateException: @Bean method AbstractMessageBrokerConfiguration.messageBrokerTaskScheduler called as bean reference for type [org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler] but overridden by non-compatible bean instance of type [com.sun.proxy.$Proxy71]. Overriding bean of same name declared in: class path resource [org/springframework/web/socket/config/annotation/DelegatingWebSocketMessageBrokerConfiguration.class]
	at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:185)
	at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:622)
	... 19 common frames omitted
Caused by: java.lang.IllegalStateException: @Bean method AbstractMessageBrokerConfiguration.messageBrokerTaskScheduler called as bean reference for type [org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler] but overridden by non-compatible bean instance of type [com.sun.proxy.$Proxy71]. Overriding bean of same name declared in: class path resource [org/springframework/web/socket/config/annotation/DelegatingWebSocketMessageBrokerConfiguration.class]
	at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.resolveBeanReference(ConfigurationClassEnhancer.java:418)
	at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.intercept(ConfigurationClassEnhancer.java:366)
	at org.springframework.web.socket.config.annotation.DelegatingWebSocketMessageBrokerConfiguration$$EnhancerBySpringCGLIB$$fca45b4f.messageBrokerTaskScheduler(<generated>)
	at org.springframework.web.socket.config.annotation.WebSocketMessageBrokerConfigurationSupport.stompWebSocketHandlerMapping(WebSocketMessageBrokerConfigurationSupport.java:76)
	at org.springframework.web.socket.config.annotation.DelegatingWebSocketMessageBrokerConfiguration$$EnhancerBySpringCGLIB$$fca45b4f.CGLIB$stompWebSocketHandlerMapping$11(<generated>)
	at org.springframework.web.socket.config.annotation.DelegatingWebSocketMessageBrokerConfiguration$$EnhancerBySpringCGLIB$$fca45b4f$$FastClassBySpringCGLIB$$25647ffa.invoke(<generated>)
	at org.springframework.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:244)
	at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.intercept(ConfigurationClassEnhancer.java:363)
	at org.springframework.web.socket.config.annotation.DelegatingWebSocketMessageBrokerConfiguration$$EnhancerBySpringCGLIB$$fca45b4f.stompWebSocketHandlerMapping(<generated>)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:564)
	at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154)

The reason is that messageBrokerTaskScheduler returns ThreadPoolTaskScheduler instead of TaskScheduler.

I understand that changing the return type to TaskScheduler may break applications that are expecting ThreadPoolTaskScheduler in the application context but 5.2.x may be a good opportunity to fix this.

Example project https://github.com/lukas-krecan/ShedLock/tree/failure/spring/shedlock-springboot22-test

StackOverflow question: https://stackoverflow.com/questions/56017382/how-to-fix-websockets-and-shedlock-compatibility-in-spring-boot-application

[rstoyanchev]

I'm going to schedule tentatively for 5.2 to give this a try. It has been come up before also in spring-cloud/spring-cloud-sleuth#410.

[rstoyanchev]

I've made this change and also updated the ThreadPoolTaskExecutor bean methods (for the 3 channels) to return TaskExecutor.

/cc @marcingrzejszczak