BindersHealthContributor throws NPE when access by actuate endpoint(health)

When a reactive(webflux) project including following pom, and no define any “Input” or “Output” channel, then get health info in browser “GET http://hostname:port/actuate/health”, ReactiveWebOperationAdapter throws exception, just disable binder actuate is OK.

 <dependency>
      <groupId>org.springframework.cloud</groupId>
      <artifactId>spring-cloud-starter-stream-kafka</artifactId>
  </dependency>

disable it is OK.

management:
  health:
    binders:
      enabled: false

java.lang.NullPointerException: null
	at reactor.core.publisher.MonoZip.subscribe(MonoZip.java:128)
	Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException: 
Assembly trace from producer [reactor.core.publisher.MonoLiftFuseable] :
	reactor.core.publisher.Mono.flatMap(Mono.java:2713)
	org.springframework.boot.actuate.endpoint.web.reactive.AbstractWebFluxEndpointHandlerMapping$ReactiveWebOperationAdapter.handle(AbstractWebFluxEndpointHandlerMapping.java:323)
Error has been observed at the following site(s):
	|_           Mono.flatMap ? at org.springframework.boot.actuate.endpoint.web.reactive.AbstractWebFluxEndpointHandlerMapping$ReactiveWebOperationAdapter.handle(AbstractWebFluxEndpointHandlerMapping.java:323)
	|_           Mono.flatMap ? at org.springframework.web.reactive.result.method.annotation.ResponseEntityResultHandler.handleResult(ResponseEntityResultHandler.java:130)
	|_             checkpoint ? Handler org.springframework.boot.actuate.endpoint.web.reactive.AbstractWebFluxEndpointHandlerMapping$ReadOperationHandler#handle(ServerWebExchange) [DispatcherHandler]
	|_             Mono.error ? at org.springframework.web.reactive.result.method.annotation.RequestMappingHandlerAdapter.handleException(RequestMappingHandlerAdapter.java:238)

[sobychacko]

@matthewhaywardmsm We were able to look further with @artembilan on the issue. Here is the problem. In your build dependency, you have this:

testImplementation 'org.springframework.cloud:spring-cloud-stream-test-support'

When you have this dependency, the test context will use this binder as the default binder. This binder does not provide any health indicators at all. This is the reason for the test failure. Since you are trying to use it with Kafka binder, I suggest that you remove this dependency and then rely on the production binder only - implementation 'org.springframework.cloud:spring-cloud-stream-binder-kafka'. When we tried it locally, the test passes. If you really want to use the test binder for any testing, you might want to isolate that into a separate module.

Hope this helps.

[sobychacko]

@matthewhaywardmsm @fanticat Closing this issue. Please re-open if you are still facing an issue with this.