How to detect thread is waiting for atomic reference

Question

I have singleton which holds connection to external service, this connection is declared as atomic reference

Connection connection = new AtomicReference<>(new Connection());

As long as this connection is used by my webservice, many threads may want to access this reference, so if one is using it at the moment, all others will wait.

I want to log information that thread is waiting for this reference, does anybody know how to detect that thread is waiting for atomic reference ?

Should I extend AtomicReference and wrap methods ? Is there any other way ?

Answer 1

AtomicReferences are a non-blocking concurrency primitive. All readers will be able to instantly dereference it, and only if there are many concurrent writers, and they are using a Compare-and-Swap action to update the reference (not the plain, unconditional set), there will be some stalling, but again not in the form of blocking; instead they will be running their busy write-retry loops. All this writing will still leave the readers uninfluenced.

So, any blocking may occur only on your Connection instance, if it has such blocking implemented. This, of course, is out of scope for any AtomicReference-related concerns.