spring-kafka

Thread name convention in spring kafka ConcurrentMessageListenerContainer consumerr

I am using spring-kafka to consume messages from a topic and we are using ConcurrentMessageListenerContainer.

Below is my application.yml

spring:
  kafka:
    listener:
      concurrency: 2
    consumer:
      group-id: test-consumer-group
      topic: CONSUMER-TOPIC

In the log we can see thread name is printed as test-consumer-group-0-C-1.

2021-10-04 11:04:41.254 [test-consumer-group-0-C-1]

I have checked the below file to see how this thread name is arrived.

Here, the thread name is like this: [group-id]-[concurrency]-C-X. Unable to understand how this X is arrived at.

Solution

  • It is well explained in the docs: https://docs.spring.io/spring-kafka/reference/kafka/receiving-messages/container-thread-naming.html

    So, with a bean name of container, threads in this container will be named container-0-C-1, container-1-C-1 etc., after the container is started the first time; container-0-C-2, container-1-C-2 etc., after a stop and subsequent start.

    So, the X in your equation belongs to the thread number when it is obtained from an executor to handle KafkaConsumer interaction. See CustomizableThreadCreator:

    /**
 * Return the thread name to use for a newly created {@link Thread}.
 * <p>The default implementation returns the specified thread name prefix
 * with an increasing thread count appended: e.g. "SimpleAsyncTaskExecutor-0".
 * @see #getThreadNamePrefix()
 */
protected String nextThreadName() {
    return getThreadNamePrefix() + this.threadCount.incrementAndGet();
}