The app was encountering this exception while submitting new task to the pool. There was not much details for the error message.

Application run failed java.util.concurrent.RejectedExecutionException: null at java.util.concurrent.ForkJoinPool.externalSubmit( at java.util.concurrent.ForkJoinPool.externalPush( at java.util.concurrent.ForkJoinPool.invokeAll(

Turns out the issue was due to the case that pool is a common pool which has been shutdown (not accepting new connections) in some other part of the application.

Originally published at on May 19, 2021.