[undertow-dev] Inconsistency in performing async task

Hi, I'm trying to perform expensive tasks (like sending email/sms etc) as an async task (using CompletableFuture API) after my undertow worker completes and i'm about to respond to the client. These tasks are supposed to work like fire and forget and I don't want to wait until the task completes and then respond to the client. I've noticed that sometimes the task doesn't execute and sometimes it does. It's inconsistent and hard to reproduce. Is there a way to be able to perform these async tasks consistently? May be i'm using wrong thread-pool? Or may be there's already a way in Undertow to do such tasks. Please comment. Thanks.