executor service never gets cleaned up

[bohnman]

Version:

7.22.0

Code Snippet

public static void main(String[] args) {
   Twilio.init("username", "password");
   Twilio.getExecutorService().submit(() -> System.out.println("Run"));
   Message.creator(new PhoneNumber("to"), new PhoneNumber("from"), "Testing.").create();
}

Steps to Reproduce

1. Run the provided code
2. Notice how the jvm doesn't shut down

The JVM doesn't shut down because there is a thread left hanging around in the executor service.

I would recommend the following:

Add a new field:

private static boolean selfCreatedExecutorService = false;

Modify setExecutorService:

public synchronized void setExecutorService(ListeningExecutorService executorService) {
    ListeningExecutorService oldExecutorService = Twilio.executorService;
    Twilio.executorService = executorService;
    
    if (oldExecutorService != null && selfCreatedExecutorService) {
        oldExecutorService.shutdownNow();
    }

    selfCreatedExectorService = false;
}

Modify getExecutorService, adding the line right after the creation and assignment of the executor service and after applying multi-threading fixes as described in #430.

selfCreatedExecutorService = true;

Add a destroy method:

public static synchronized void destroy() {
    if (executorService != null && selfCreatedExecutorService) {
        executorService.shutdownNow();
    }
}

Add a shutdown hook:

static {
   Runtime.getRuntime().addShutdownHook(new Thread(() -> Twilio.destroy()));
}

Finally, document that it is recommended to call Twilio.destroy before JVM shutdown. However, the shutdown hook will take care of it as a fallback.

[atbaker]

Hey @bohnman - really appreciate these thoughtful issues. Our team took a look at them and agree they're good suggestions, but I can't say exactly when we'll be able to implement them.

I'd love to send you a Twilio t-shirt to thank you for your thoughtful issues, though. Can you shoot me an email at [email protected] with your address and t-shirt size?

Thank you!

[bohnman]

email sent. Thanks!

[thinkingserious]

Thanks @bohnman!

This issue has been added to our internal backlog to be prioritized. Pull requests and +1s on the issue summary will help it move up the backlog.

With best regards,

Elmer