Dispatcher has no subscribers for channel 'employee-management-1.kafka-log-publisher' - spring

Question

I have done below configuration and java code to send a message to the kafka topic. I want to send the message only.
I am using Spring boot and kafka integration.
Kafka application has been started from Docker
Spring Boot Application connects the kafka by simple configuration
pom.xml
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.5.1</version>
<relativePath /> <!-- lookup parent from repository -->
</parent>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>2020.0.3</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<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>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-stream-kafka</artifactId>
</dependency>
application.yml
spring:
kafka:
bootstrap-servers:
- localhost:19091
cloud:
stream:
bindings:
kafka-log-publisher:
binder: kafka
destination: com.tonitingaurav.kafka.log
default-binder: kafka
kafka:
binder:
brokers:
- localhost:19091
Message Channel Bean
#Configuration
#EnableIntegration
public class LogProducerKafkaConfig {
#Bean("kafka-log-publisher")
public MessageChannel kafkaLogPublisher() {
return new DirectChannel();
}
}
Log Event Publisher
#Component
public class LogEventPublisher {
#Autowired
#Qualifier("kafka-log-publisher")
MessageChannel messageChannel;
public void logMessage(Log log) {
Message<Log> message = MessageBuilder.withPayload(log).build();
messageChannel.send(message);
}
}
Rest End Point Publishing Message
public class EmployeeController {
private static final Logger LOGGER = LoggerFactory.getLogger(EmployeeController.class);
#Autowired
private LogEventPublisher logEventPublisher;
#GetMapping
public ResponseEntity<Employees> getAll() {
LOGGER.info("Getting All Employees");
logEventPublisher.logMessage(new Log("Getting All Employees"));
}
}
Below is the exception trace I am getting while excute the rest end point.
org.springframework.messaging.MessageDeliveryException: Dispatcher has no subscribers for channel 'employee-management-1.kafka-log-publisher'.; nested exception is org.springframework.integration.MessageDispatchingException: Dispatcher has no subscribers, failedMessage=GenericMessage [payload=com.tonitingaurav.microservice.audit.Log#3e170b0f, headers={id=e549b9d1-8ada-8032-2ff9-6cf1e02bae53, timestamp=1638119747020}]
at org.springframework.integration.channel.AbstractSubscribableChannel.doSend(AbstractSubscribableChannel.java:76) ~[spring-integration-core-5.5.0.jar:5.5.0]
at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:317) ~[spring-integration-core-5.5.0.jar:5.5.0]
at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:272) ~[spring-integration-core-5.5.0.jar:5.5.0]
at com.tonitingaurav.microservice.event.log.LogEventPublisher.logMessage(LogEventPublisher.java:21) ~[classes/:na]
at com.tonitingaurav.microservice.controller.EmployeeController.getAll(EmployeeController.java:49) ~[classes/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_291]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_291]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_291]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_291]
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:197) ~[spring-web-5.3.8.jar:5.3.8]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:141) ~[spring-web-5.3.8.jar:5.3.8]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106) ~[spring-webmvc-5.3.8.jar:5.3.8]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:894) ~[spring-webmvc-5.3.8.jar:5.3.8]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808) ~[spring-webmvc-5.3.8.jar:5.3.8]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.3.8.jar:5.3.8]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1063) ~[spring-webmvc-5.3.8.jar:5.3.8]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963) ~[spring-webmvc-5.3.8.jar:5.3.8]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) [spring-webmvc-5.3.8.jar:5.3.8]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) [spring-webmvc-5.3.8.jar:5.3.8]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:626) [tomcat-embed-core-9.0.46.jar:4.0.FR]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) [spring-webmvc-5.3.8.jar:5.3.8]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) [tomcat-embed-core-9.0.46.jar:4.0.FR]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227) [tomcat-embed-core-9.0.46.jar:9.0.46]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) [tomcat-embed-core-9.0.46.jar:9.0.46]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) [tomcat-embed-websocket-9.0.46.jar:9.0.46]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) [tomcat-embed-core-9.0.46.jar:9.0.46]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) [tomcat-embed-core-9.0.46.jar:9.0.46]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) [spring-web-5.3.8.jar:5.3.8]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.3.8.jar:5.3.8]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) [tomcat-embed-core-9.0.46.jar:9.0.46]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) [tomcat-embed-core-9.0.46.jar:9.0.46]
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) [spring-web-5.3.8.jar:5.3.8]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.3.8.jar:5.3.8]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) [tomcat-embed-core-9.0.46.jar:9.0.46]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) [tomcat-embed-core-9.0.46.jar:9.0.46]
at org.springframework.cloud.sleuth.instrument.web.servlet.TracingFilter.doFilter(TracingFilter.java:89) [spring-cloud-sleuth-instrumentation-3.0.3.jar:3.0.3]
at org.springframework.cloud.sleuth.autoconfig.instrument.web.LazyTracingFilter.doFilter(TraceWebServletConfiguration.java:114) [spring-cloud-sleuth-autoconfigure-3.0.3.jar:3.0.3]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) [tomcat-embed-core-9.0.46.jar:9.0.46]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) [tomcat-embed-core-9.0.46.jar:9.0.46]
at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.doFilterInternal(WebMvcMetricsFilter.java:96) [spring-boot-actuator-2.5.1.jar:2.5.1]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.3.8.jar:5.3.8]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) [tomcat-embed-core-9.0.46.jar:9.0.46]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) [tomcat-embed-core-9.0.46.jar:9.0.46]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) [spring-web-5.3.8.jar:5.3.8]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.3.8.jar:5.3.8]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) [tomcat-embed-core-9.0.46.jar:9.0.46]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) [tomcat-embed-core-9.0.46.jar:9.0.46]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) [tomcat-embed-core-9.0.46.jar:9.0.46]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) [tomcat-embed-core-9.0.46.jar:9.0.46]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542) [tomcat-embed-core-9.0.46.jar:9.0.46]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143) [tomcat-embed-core-9.0.46.jar:9.0.46]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.46.jar:9.0.46]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) [tomcat-embed-core-9.0.46.jar:9.0.46]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357) [tomcat-embed-core-9.0.46.jar:9.0.46]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374) [tomcat-embed-core-9.0.46.jar:9.0.46]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) [tomcat-embed-core-9.0.46.jar:9.0.46]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:893) [tomcat-embed-core-9.0.46.jar:9.0.46]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1707) [tomcat-embed-core-9.0.46.jar:9.0.46]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.46.jar:9.0.46]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_291]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_291]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.46.jar:9.0.46]
at java.lang.Thread.run(Thread.java:748) [na:1.8.0_291]
Caused by: org.springframework.integration.MessageDispatchingException: Dispatcher has no subscribers
at org.springframework.integration.dispatcher.UnicastingDispatcher.doDispatch(UnicastingDispatcher.java:139) ~[spring-integration-core-5.5.0.jar:5.5.0]
at org.springframework.integration.dispatcher.UnicastingDispatcher.dispatch(UnicastingDispatcher.java:106) ~[spring-integration-core-5.5.0.jar:5.5.0]
at org.springframework.integration.channel.AbstractSubscribableChannel.doSend(AbstractSubscribableChannel.java:72) ~[spring-integration-core-5.5.0.jar:5.5.0]
... 62 common frames omitted

Answer 1

Your kafka-log-publisher indeed has o subscribers, hence the error. You simply defined message channel and sending message to it and since it does not have any subscriber you see the error.
What made you think that it is somehow connected to Kafka?
If you simply want to produce a Message and send it to a binding destination, you have two choices. One is via the Supplier and another via the StreamBridge

Answer 2

Producer code starts working by adding the below code.
#Bean
#ServiceActivator(inputChannel = KAFKA_LOG_PUBLISHER)
public AbstractMappingMessageRouter getMessageHandler() {
return new AbstractMappingMessageRouter() {
#Override
protected List<Object> getChannelKeys(Message<?> message) {
BindingProperties bindingProperties = binders.getBindings().get(KAFKA_LOG_PUBLISHER);
return Collections.singletonList(bindingProperties.getDestination());
}
};
}
KafkaBinder: to read application.yml file's spring.cloud.stream.bindings
#ConfigurationProperties(prefix = "spring.cloud.stream")
#NoArgsConstructor
#Getter
#Setter
#Component
public class KafkaBinders {
private Map<String, BindingProperties> bindings = ImmutableMap.of();
}