KafkaBindingRebalanceListener Bean not autowired by KafkaMessageChannelBinder Bean

Question

Documentation is pretty straight forward which suggests exposing a Bean of type KafkaBindingRebalanceListener and onPartitiosnAssigned method would be called internally. I'm trying to do the same and somehow while spring framework creates its KafkaMessageChannelBinder Bean the ObjectProvider.getIfUnique() always return null as it not able to find the required bean. It seems when application starts SpringFramework strats creating its Beans first and isnt able to find the Rebalance Listener Bean as it is not yet created. Following are the three code snippets from project. Please help if im missing anything to instruct application to create Beans in application package first before going to Spring Framework.

RebalanceListener

package io.spring.dataflow.sample.seekoffset.config;

import org.apache.kafka.clients.consumer.Consumer;
import org.apache.kafka.common.TopicPartition;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.cloud.stream.binder.kafka.KafkaBindingRebalanceListener;
import org.springframework.stereotype.Component;

import java.util.Collection;

@Component
public class KafkaRebalanceListener implements KafkaBindingRebalanceListener {
    Logger logger = LoggerFactory.getLogger(SeekOffsetConfig.class);

    @Override
    public void onPartitionsAssigned(String bindingName, Consumer<?, ?> consumer, Collection<TopicPartition> partitions, boolean initial) {
        logger.debug("onPartitionsAssigned");
    }
}

ConfigClass

package io.spring.dataflow.sample.seekoffset.config;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.cloud.stream.annotation.EnableBinding;
import org.springframework.cloud.stream.annotation.StreamListener;
import org.springframework.cloud.stream.messaging.Sink;
import org.springframework.messaging.Message;

@EnableBinding(Sink.class)
public class SeekOffsetConfig {
    Logger logger = LoggerFactory.getLogger(SeekOffsetConfig.class);

    @StreamListener(Sink.INPUT)
    public void receiveMessage(Message<String> message) {
        logger.debug("receiveMessage()");
    }
}

ApplicationClass

package io.spring.dataflow.sample.seekoffset;

import io.spring.dataflow.sample.seekoffset.config.KafkaRebalanceListener;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.ComponentScan;

@SpringBootApplication
public class SeekOffsetApplication {
    Logger logger = LoggerFactory.getLogger(SeekOffsetApplication.class);

    public static void main(String[] args) {
        SpringApplication.run(SeekOffsetApplication.class, args);
    }
}

score 1 · Accepted Answer · answered Jul 29 '20 at 16:19

1

What version are you using? This works fine for me with Boot 2.3.2 and Hoxton.SR6:

@SpringBootApplication
@EnableBinding(Sink.class)
public class So63157778Application {

    public static void main(String[] args) {
        SpringApplication.run(So63157778Application.class, args);
    }

    @StreamListener(Sink.INPUT)
    public void listen(String in) {
        System.out.println(in);
    }

    @Bean
    KafkaBindingRebalanceListener rebal() {
        return new KafkaBindingRebalanceListener() {

            @Override
            public void onPartitionsAssigned(String bindingName, Consumer<?, ?> consumer,
                    Collection<TopicPartition> partitions, boolean initial) {
                System.out.println(bindingName + " assignments: " + partitions + ", initial call :" + initial);
            }

        };
    }

}

input assignments: [input-0], initial call :true

This works for me too:

@SpringBootApplication
@EnableBinding(Sink.class)
public class So63157778Application {

    public static void main(String[] args) {
        SpringApplication.run(So63157778Application.class, args);
    }

    @StreamListener(Sink.INPUT)
    public void listen(String in) {
        System.out.println(in);
    }

}

@Component
class Foo implements KafkaBindingRebalanceListener {

    @Override
    public void onPartitionsAssigned(String bindingName, Consumer<?, ?> consumer,
            Collection<TopicPartition> partitions, boolean initial) {
        System.out.println(bindingName + " assignments: " + partitions + ", initial call :" + initial);
    }

}

answered Jul 29 '20 at 16:19

Gary Russell

166,535
14
146
179

Your code surely works. I tried an empty project with just your code and it did work. It seems i've messed up the YML config file and that is causing the issue. Now I'll try to figure that out. Thanks a bunch for your quick help. – hannan Jul 29 '20 at 18:55
@hannan Can you please tell us what did you do? I am also using boot 2.3.2 and Hoxton.SR6 and I am not able to autowire my rebalance listener – Sahil333 Apr 01 '21 at 15:49
It doesn't work if you are using multiple binders (or a named single binder). spring-cloud-stream 3.1 provides a new interface `BinderCustomizer` which can be used to inject such beans into named binders. https://docs.spring.io/spring-cloud-stream/docs/3.1.2/reference/html/spring-cloud-stream.html#binder-customizer If you are only using a single binder, don't name it. – Gary Russell Apr 01 '21 at 15:58
Thanks @GaryRussell. I am aware of multiple-binders issue. But can you please elaborate on named single binder? In my application, I only have one binder but not sure what named binder is. – Sahil333 Apr 01 '21 at 16:03
Is it a single binder defined under - ```spring.cloud.stream.binders.binder-name``` – Sahil333 Apr 01 '21 at 16:11
1

If you give a single binder a name (referring to the binder name in the binding), it is using multi-binder support (albeit with just one binder). The same problems occur because the binder is loaded in a different application context to the rebalance listener. – Gary Russell Apr 01 '21 at 16:16
I see. Thanks for the answer :D – Sahil333 Apr 01 '21 at 18:18

KafkaBindingRebalanceListener Bean not autowired by KafkaMessageChannelBinder Bean

1 Answers1

Linked