Resource Constrained Thread Per Task Executor

[Colin Redmond]

Thanks for sharing that. It is a nice solution to my problem. I wouldn't have thought about having a ThreadFactory with a Semaphore for a ThreadFactory. But it looks simple and solves the problem.

________________________________
From: loom-dev <loom-dev-retn at openjdk.org> on behalf of Daniel Avery <danielaveryj at gmail.com>
Sent: May 13, 2024 6:56 PM
To: loom-dev <loom-dev at openjdk.java.net>
Subject: Re: Resource Constrained Thread Per Task Executor

If you did need to integrate a semaphore into an ExecutorService, you might find it easier to implement a ThreadFactory, and then leverage the utility methods in Executors to get an ExecutorService.

```

Semaphore sem = new Semaphore(permits);

ThreadFactory factory1 = Thread.ofVirtual().factory();

ThreadFactory factory2 = runnable -> {

    try {

        sem.acquire();

        return factory1.newThread(() -> {

            try {

                runnable.run();

            } finally {

                sem.release();

            }

        });

    } catch (InterruptedException ie) { // interrupted in acquire()

        Thread.currentThread().interrupt();

        throw new RuntimeException(ie);

    } catch (Throwable t) { // threw in newThread()

        sem.release();

        throw t;

    }

};

ExecutorService es = Executors.newThreadPerTaskExecutor(factory2);

```

- Daniel
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