SpringBoot @SqsListener - not working - with Exception - TaskRejectedException

Question

I have a AWS SQS with 5000 messages already on the Queue (Sample Message looks like this 'Hello @ 1') I created a SpringBoot Application and inside one of the Component Classes create a method to read messages from the SQS.

package com.example.aws.sqs.service;

import org.springframework.cloud.aws.messaging.listener.SqsMessageDeletionPolicy;
import org.springframework.cloud.aws.messaging.listener.annotation.SqsListener;
import org.springframework.stereotype.Component;
import lombok.extern.slf4j.Slf4j;

@Component
@Slf4j
public class MessageReceiverService {   

@SqsListener(value = { "${cloud.aws.sqs.url}" }, deletionPolicy = SqsMessageDeletionPolicy.ALWAYS)
public void readMessage(String message){
    log.info("Reading Message... {}", message);
}

}

My main SpringBoot Class

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

Exception I get when the application runs:

s.c.a.m.l.SimpleMessageListenerContainer : An Exception occurred while polling queue '<my sqs name>'. The failing operation will be retried in 10000 milliseconds
org.springframework.core.task.TaskRejectedException: Executor [java.util.concurrent.ThreadPoolExecutor@7c1594a5[Running, pool size = 3, active threads = 3, queued tasks = 0, completed tasks = 20]] did not accept task: org.springframework.cloud.aws.messaging.listener.SimpleMessageListenerContainer$SignalExecutingRunnable@1cbd9ef2
at org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor.execute(ThreadPoolTaskExecutor.java:309) ~[spring-context-5.0.7.RELEASE.jar:5.0.7.RELEASE]
at org.springframework.cloud.aws.messaging.listener.SimpleMessageListenerContainer$AsynchronousMessageListener.run(SimpleMessageListenerContainer.java:286) ~[spring-cloud-aws-messaging-2.0.0.RELEASE.jar:2.0.0.RELEASE]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [na:1.8.0_65]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_65]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_65]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_65]
at java.lang.Thread.run(Thread.java:745) [na:1.8.0_65]
Caused by: java.util.concurrent.RejectedExecutionException: Task org.springframework.cloud.aws.messaging.listener.SimpleMessageListenerContainer$SignalExecutingRunnable@1cbd9ef2 rejected from java.util.concurrent.ThreadPoolExecutor@7c1594a5[Running, pool size = 3, active threads = 2, queued tasks = 0, completed tasks = 20]
at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:2047) ~[na:1.8.0_65]
at java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:823) [na:1.8.0_65]
at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1369) [na:1.8.0_65]
at org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor.execute(ThreadPoolTaskExecutor.java:306) ~[spring-context-5.0.7.RELEASE.jar:5.0.7.RELEASE]
... 6 common frames omitted

I am NOT configuring any custom Executor services. Using the preconfigured Spring Beans. springBootVersion = '2.0.3.RELEASE' springCloudVersion = 'Finchley.RELEASE'

Answer 1

Adding @EnableSqs annotation on the MessageRecieverService

Answer 2

setting the max number of messages seems to solve the issue:

@Bean
public SimpleMessageListenerContainerFactory simpleMessageListenerContainerFactory(AmazonSQSAsync amazonSQS){
    SimpleMessageListenerContainerFactory factory = new SimpleMessageListenerContainerFactory();
    factory.setAmazonSqs(amazonSQS);
    factory.setMaxNumberOfMessages(10);
    return factory;
}