TraceAsyncCustomAutoConfiguration configures a BeanPostProcessor that changes the type of AsyncConfigurer beans and breaks dependency resolution

[wilkinsona]

Describe the bug

Please see spring-projects/spring-boot#29151 for details.

Sample

This zipped Maven project will reproduce the problem using Sleuth 3.0.5 without really involving Boot. Running the main method will fail:

12:12:49.395 [main] DEBUG org.springframework.context.annotation.AnnotationConfigApplicationContext - Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@2401f4c3
12:12:49.414 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalConfigurationAnnotationProcessor'
12:12:49.536 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.event.internalEventListenerProcessor'
12:12:49.538 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.event.internalEventListenerFactory'
12:12:49.539 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalAutowiredAnnotationProcessor'
12:12:49.540 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalCommonAnnotationProcessor'
12:12:49.543 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'asyncBeanPostProcessor'
12:12:49.559 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'gh29151Application'
12:12:49.560 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'exampleConfigurer'
12:12:49.606 [main] DEBUG org.springframework.context.annotation.AnnotationConfigApplicationContext - Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@2401f4c3, started on Wed Jan 19 12:12:49 GMT 2022
Exception in thread "main" org.springframework.beans.factory.BeanNotOfRequiredTypeException: Bean named 'exampleConfigurer' is expected to be of type 'com.example.demo.Gh29151Application$Example' but was actually of type 'org.springframework.cloud.sleuth.instrument.async.LazyTraceAsyncCustomizer'
	at org.springframework.beans.factory.support.AbstractBeanFactory.adaptBeanInstance(AbstractBeanFactory.java:417)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:398)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:213)
	at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1160)
	at com.example.demo.Gh29151Application.main(Gh29151Application.java:14)

The failure does not occur without the TraceAsyncCustomAutoConfiguration bean post-processor.

[Saljack]

Here is a workaround if you do not want to disable Sleuth for async (spring.sleuth.async.enabled=false). You have to exclude autoconfiguration TraceAsyncCustomAutoConfiguration and wrap your executor with LazyTraceExecutor:

spring:
  autoconfigure:
    exclude:
      - org.springframework.cloud.sleuth.autoconfig.instrument.async.TraceAsyncCustomAutoConfiguration

@EnableAsync
@Configuration
public class AsyncConfig implements AsyncConfigurer {

  private final BeanFactory beanFactory;

  public AsyncConfig(BeanFactory beanFactory) {
    this.beanFactory = beanFactory;
  }

  @Override
  public Executor getAsyncExecutor() {
    Executor executor = new ThreadPoolTaskExecutor(); // create or configure your executor
    return new LazyTraceExecutor(beanFactory, executor);
  }
}

[marcingrzejszczak]

This is blocked by spring-projects/spring-framework#27953