[FIXED] Cannot requesting API of Spring-Boot while reading asynchronously E-Mail via IMAPS

Issue

following situation. I have a Spring-Boot Application which handles two main features.

1. Reading asynchronously E-Mail from Server via IMAPS. (See below for configuration)
2. Providing an API for generating and reading order (this is my business object)

The Problem is curious. If I start my Application without connection to IMAP and reading E-Mails I'm able to make any request to my API. But in the case of starting the E-mail Connection and reading E-Mails I'm not able to make any request to my API.

I receive always following error:

Error: connect ECONNREFUSED 127.0.0.1:8081

Can anyone help me and give me an advise how to handle this?

// Email Connection
        Store store = null;
        var props = new Properties();
        props.setProperty("mail.store.protocol", mailProperties.getProtocol());
        try {
            var session = Session.getInstance(props, null);
            store = session.getStore();
            store.connect(
                    mailProperties.getHost(),
                    mailProperties.getUsername(),
                    decodeAsString(mailProperties.getPassword())
            );
            var inbox = store.getFolder("INBOX");
            inbox.open(Folder.READ_WRITE);
            waitForNewMessages(inbox);
       ...

       inbox.addMessageCountListener(new MessageCountAdapter() {
            @Override
            @SneakyThrows
            public void messagesAdded(MessageCountEvent ev) {
                for (Message message : ev.getMessages()) {
                    log.info("Message received subject={}, from={}", message.getSubject(), message.getFrom());
                    emailMessageHandler.handle(message);
                }
            }
        });
       ...


    private void waitForNewMessages(Folder inbox) throws MessagingException {
        while (inbox.isOpen()) {
            //every 25 minutes poke the server with a inbox.getMessageCount() to keep the connection active/open
            var scheduler = Executors.newScheduledThreadPool(1);
            final Runnable pokeInbox = () -> {
                try {
                    inbox.getMessageCount();
                } catch (MessagingException ex) {
                    //nothing doin'
                }
            };
            scheduler.schedule(pokeInbox, 25, TimeUnit.MINUTES);
            ((IMAPFolder) inbox).idle();
        }
    }

Solution

After researching the whole www, I found the following solution IdleManager. IdleManager uses an ExecutorService for listening for all events from the SMTP-Server and it doesn't block the Web-Application for other incoming request.

For getting in touch and more information you can see the following documentation. IdleManager

Answered By - ramazan86