Inconsistent behavior with CompletableFuture and custom Executor in Java 17
I need help solving I'm a bit lost with I've been banging my head against this for hours. Quick question that's been bugging me - I'm experiencing inconsistent behavior when using `CompletableFuture` with a custom `Executor` in my Java 17 application. The tasks I submit to the `CompletableFuture` sometimes execute as expected, but other times they seem to hang indefinitely. Here's the code that sets up the `CompletableFuture`: ```java import java.util.concurrent.*; public class CompletableFutureTest { private static final ExecutorService executor = Executors.newFixedThreadPool(2); public static void main(String[] args) { CompletableFuture<Void> future = CompletableFuture.runAsync(() -> { try { Thread.sleep(2000); System.out.println("Task completed"); } catch (InterruptedException e) { e.printStackTrace(); } }, executor); future.thenRun(() -> System.out.println("Next task executed")); executor.shutdown(); } } ``` In this example, I expect the console to print "Task completed" followed by "Next task executed" after a 2-second delay. However, sometimes I see the second message printed immediately, and at other times, the application just hangs without any output. I've tried a couple of things: 1. Adjusting the thread pool size in the `ExecutorService` to see if it affects execution. 2. Adding a timeout to the `CompletableFuture` to see if that resolves the hanging scenario. Here's how I added a timeout: ```java future.orTimeout(5, TimeUnit.SECONDS) .exceptionally(ex -> { System.out.println("behavior: " + ex.getMessage()); return null; }); ``` However, the timeout doesn’t seem to trigger either when the tasks hang. I'm concerned that there might be something fundamental I'm missing about how `CompletableFuture` interacts with the provided executor. Is there any additional configuration or best practice I should consider to avoid these inconsistencies? I would appreciate any insights on where I might be going wrong or if there are nuances with `CompletableFuture` in Java 17 that I need to be aware of. For context: I'm using Java on Ubuntu. Has anyone else encountered this? I've been using Java for about a year now. Any pointers in the right direction? The project is a web app built with Java. I'm working in a Linux environment. Thanks for taking the time to read this! The stack includes Java and several other technologies.