Starting Spring Boot application without check for Kafka Server - spring

Question

I have got an application that uses SpringBoot 2.10.0.Release and kafka in the version 2.10.0. The application has got a simple producer and consumer: The sender works with KafkaTemplate and the consumer with KafkaListener.
What I try to achieve is to be able to start the SpringBoot application even if the KafkaServer is not running.
Currently without a running KafkaBroker the application cannot be started with this error message:
org.springframework.context.ApplicationContextException:
Failed to start bean 'org.springframework.kafka.config.internalKafkaListenerEndpointRegistry';
nested exception is org.apache.kafka.common.errors.TimeoutException
Is there a way to achieve this and if yes could anybody give me hint or a keyword how to manage this?

Answer 1

When running the Spring-Boot application with a KafkaListener, the listener will per default try to listen to Kafka. If the KafkaBroker is invalid or missing, then you will get a org.apache.kafka.common.KafkaException.
You can change the default behaviour of the container factory by setting the autoStartup property to false. One way to do this is by adding autoStartup = "false" element to your KafkaListener annotation:
#KafkaListener(topics = "some_topic", autoStartup = "false")
public void fooEventListener(){
Now your spring boot application will start. You will still get an error when trying to use the KafkaListener if the broker is still down or invalid, but you will now be able to handle the error within your Java code instead of a Spring Boot server crash.
Documentation about KafkaListner autoStartup element.
It have to be mentioned that the error you are receiving (TimeoutException) is not because the broker is down, it is what Kafka will throw if the buffer is full.
The batch records will then be removed from the queue and will not be delivered to the broker. This error will not be the reason for you application using Kafka not to start.