How to limit number of threads all concurrent methods at once

Question

I am working on a legacy project which uses Java 8, Spring, HikariCP, and MySQL. Microservices' methods are triggered with a Kafka topic and start a reporting operation. Almost all triggered methods have this and some of them have the same usage inside their blocks.

new ForkJoinPool().submit(() -> { users.parallelStream().forEach(user ->

The application creates 8-9k threads and all of them try to get or create a record. However, the database couldn't handle these requests and started to throw exceptions and Zabbix sends mails about heap memory usage above %90:

Caused by: java.sql.SQLTransientConnectionException: HikariPool-2 - Connection is not available, request timed out after 30000ms.

When I check the database and see the variable for max_connections = 600, but this is not enough.

I want to set a limit for thread count for the application level. I tried setting these parameters but the thread size doesn't decrease.

SPRING_TASK_EXECUTION_POOL_QUEUE-CAPACITY , SPRING_TASK_EXECUTION_POOL_MAX-SIZE, -Djava.util.concurrent.ForkJoinPool.common.parallelism

Is there any property to solve this problem?

Answer 1

I have changed all new ForkJoinPool() to ForkJoinPool.commonPool() and use this parameter to control thread creation -Djava.util.concurrent.ForkJoinPool.common.parallelism after that I have fixed my problem.