Spring cloud stream multi binder - Error KStreamBinderConfiguration required a single bean, but 2 were found

Question

I have a use case where a single kafka stream processing MS will have a processor and a consumer which will consume the processor output message. Similar to below sample in github

https://github.com/spring-cloud/spring-cloud-stream-samples/tree/master/kafka-streams-samples/kafka-streams-message-channel

while executing the above sample I getting following error

***************************
APPLICATION FAILED TO START
***************************

Description:

Parameter 0 of method provisioningProvider in org.springframework.cloud.stream.binder.kafka.streams.KStreamBinderConfiguration required a single bean, but 2 were found:
    - kafkaBinderConfigurationProperties: defined by method 'kafkaBinderConfigurationProperties' in org.springframework.cloud.stream.binder.kafka.streams.MutliBinderPropertiesConfiguration
    - binderConfigurationProperties: defined by method 'binderConfigurationProperties' in class path resource [org/springframework/cloud/stream/binder/kafka/streams/KafkaStreamsBinderSupportAutoConfiguration.class]


Action:

Consider marking one of the beans as @Primary, updating the consumer to accept multiple beans, or using @Qualifier to identify the bean that should be consumed

Answer 1

This seems to be some kind of screw-up from the side of Spring Cloud.

This cryptic thread proposed downgrading the dependencies (org.springframework.cloud:spring-cloud-stream-binder-kafka-streams and org.springframework.cloud:spring-cloud-stream for me) from 3.0.1.RELEASE to 3.0.0.RELEASE.

This was indeed the fix for my version of this problem, and I guess it is for you, too.

Answer 2

This error occurred for me while I was using @SpringBootApplication and @EnableBinding( Processor.class ) outside of the class that was running my project, in conjunction with both of the dependencies below.

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

Both of these dependencies provide a configuration for provisioningProvider, so to resolve the issue, we must specify which configuration to use.

In your application.yml file, set a default binder to resolve this issue.

spring:
   cloud:
      stream:
         kafka:
            binder:
               brokers: localhost
               defaultBrokerPort: 9092
         bindings:
           output:
             binder: name-of-target-binder
             destination: sample-topic
         defaultBinder: name-of-target-binder

The documentation here, Section 7.4 Multiple Binders on the Classpath, provides further insight into this issue.

Answer 3

I had a similar issue, and I fixed it by adding in my pom:

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-actuator</artifactId>
    </dependency>