Cannot run two #Input SubscribleChannels in spring-boot app - spring

Question

I'm developing a spring cloud kafka app with kafka streams binder. I have two #Input and one #Output as the following:
internal interface OfferChannel {
companion object {
const val CREATE_OFFER = "create-offer"
const val CREATE_OFFER_COUNTER = "create-offer-counter"
const val OFFER_CREATED = "offer-created"
}
#Input(OFFER_CREATED)
fun offerCreatedChannel(): SubscribableChannel
#Input(CREATE_OFFER_COUNTER)
fun createOfferAdminChannel(): SubscribableChannel
#Output(CREATE_OFFER)
fun createOfferChannel(): MessageChannel
}
During application startup I am getting the following error:
org.springframework.cloud.stream.binder.BinderException: Exception thrown while starting consumer:
at org.springframework.cloud.stream.binder.AbstractMessageChannelBinder.doBindConsumer(AbstractMessageChannelBinder.java:455)
at org.springframework.cloud.stream.binder.AbstractMessageChannelBinder.doBindConsumer(AbstractMessageChannelBinder.java:99)
at org.springframework.cloud.stream.binder.AbstractBinder.bindConsumer(AbstractBinder.java:144)
at org.springframework.cloud.stream.binding.BindingService.lambda$rescheduleConsumerBinding$0(BindingService.java:171)
at org.springframework.scheduling.support.DelegatingErrorHandlingRunnable.run(DelegatingErrorHandlingRunnable.java:54)
at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:304)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
at java.base/java.lang.Thread.run(Thread.java:834)
Caused by: java.lang.IllegalStateException: Only one LastSubscriberMessageHandler is allowed
at org.springframework.cloud.stream.binder.BinderErrorChannel.subscribe(BinderErrorChannel.java:44)
at org.springframework.cloud.stream.binder.AbstractMessageChannelBinder.registerErrorInfrastructure(AbstractMessageChannelBinder.java:704)
at org.springframework.cloud.stream.binder.AbstractMessageChannelBinder.registerErrorInfrastructure(AbstractMessageChannelBinder.java:627)
at org.springframework.cloud.stream.binder.kafka.KafkaMessageChannelBinder.createConsumerEndpoint(KafkaMessageChannelBinder.java:578)
at org.springframework.cloud.stream.binder.kafka.KafkaMessageChannelBinder.createConsumerEndpoint(KafkaMessageChannelBinder.java:135)
at org.springframework.cloud.stream.binder.AbstractMessageChannelBinder.doBindConsumer(AbstractMessageChannelBinder.java:402)
... 10 common frames omitted
Additionally, if I remove one of the #Input declarations the application starts successfully. Any suggestions what it going wrong here ?

Answer 1

Something is related to the version of the libraries.
For example my task was to switch to 2.4 kafka client with org.springframework.boot version 2.2.3.RELEASE. Firstly I updated to the latest 2.2.10.RELEASE version, you would say it's not a big deal since it's minor version change, well it appears that 2.2.10.RELEASE caused this bug and I had to revert it to 2.2.9.RELEASE.
Next step for my kafka version increase was to follow this tutorial:
https://docs.spring.io/spring-kafka/reference/html/#update-deps
So I set implementation "org.springframework.kafka:spring-kafka:2.4.9.RELEASE", well guess what? 2.4.9.RELEASE also caused the same problem, so I downgraded it to 2.4.8.RELEASE.
My working config (not using latest minor versions):
plugins {
id 'org.springframework.boot' version '2.2.9.RELEASE'
}
ext {
springKafkaVersion = '2.4.8.RELEASE'
kafkaVersion = '2.4.1'
}
dependencies {
implementation "org.springframework.kafka:spring-kafka:$springKafkaVersion"
implementation "org.apache.kafka:kafka-clients:$kafkaVersion"
implementation "org.apache.kafka:kafka-streams:$kafkaVersion"
testImplementation "org.springframework.kafka:spring-kafka-test:$springKafkaVersion"
testImplementation "org.apache.kafka:kafka-clients:$kafkaVersion:test"
}
So the suggestion is to look at your library versions and try to upgrade/downgrade accordingly.

Answer 2

I have the same error when updating spring boot version from 2.2.9 to 2.2.10, current work around is to use the old version. You can check your spring boot version and have a try