I am writing a new release of my Spring CQRS Module(link1, link2), including a parallel execution feature. Concurrency issues can be hard to solve especially with new programming language features.

The issue with Java 8 promises

However, I am encountering several issues with the Java 8 promises aka CompletableFutures.

My issues are :

• I am using a dedicated ForkNodePool but some promises are stilled created outside my pool
• Some threads are slow to die (WAITING state is too long)
• Completable.allOf is creating promises in the common ForkNodePool
• I had an exceeded waiting for thread exception

Here are two links that are helping me a lot to solve these problems :

• Java Parallel Calamity: link
• The Java Fork/Join Framework: link2

These two articles are well documented and explain in detail how Java/Threads/Java/JVM/Promises and parallel streams work.