App hang when using promises/async on connecting

[Aykelith]

I'm using NodeJS 8.11.3 with Monk 6.0.6 and I have the next piece of code:

function monkConnect(url) {
    return new Promise(resolve => {
        resolve(monk(url));
    });
}

await monkConnect("some valid url");

I have tried in so many ways to make this works( using the callback from monk(url), making the function async and calling await on monk, and so many methods) and the code just freeze/hang and nothing happen and I don't know how to resolve it. Please some help.

[szm1]

I ran into this problem yesterday as well and have tried all manner of things. I'm not sure if the monk constructor is returning a proper promise. It sets up a bunch of functions on it including a then function:

Manager.prototype.then = function (fn) {
  return new Promise(function (resolve, reject) {
    this.once('open', resolve)
    this.once('error-opening', reject)
  }.bind(this)).then(fn.bind(null, this))
}

However, if mongo isn't actually running when monk tries to connect, it doesn't use the reject function passed into the then function above, it just breaks out and I get an unhandled promise rejection error.

It would be great if this problem could get fixed, because I'm trying to use async/await to wait until monk connects before trying to get some data out of the database, but that's not possible currently.

[nevyn-lookback]

Monk constructor is indeed not returning a promise at all. It's returning a function that vaguely looks like a promise. Not only that: the promise is also not resolving to the monk instance, so you can't do const db = await monk()!

I would strongly encourage monk's maintainer to either make monk() actually return a real promise and not a make-believe one; or separating connection logic into a connect(): Promise<> function.

A hack meanwhile:

const db = monk(mongoUrl);
await monk(mongoUrl).then(function() {});

If I could also request JS developers everywhere to stop returning type-punned results that look like many different things, and instead be a single value, I'd be very happy :(

[mathieudutour]

Happy to accept a PR

[nevyn-lookback]

Sorry for my tone. Had a really bad day. Working on a PR.

[toniov]

I just want to note that the hack above is creating two connections actually, but we are not getting the second connection instance back, so it's impossible to close (causing the Node process to stay alive even if all the operations are done).

[Darkhogg]

A year later, this is still a problem, and I don't think there's a solution that doesn't break compatibility.

The only workaround I've been able to use is:

function connect (uri) {
    const db = monk(uri);
    db.then = null;

    return new Promise((accept, reject) => {
      db.once('open', () => accept(db));
      db.once('error-opening', reject);
    });
}

Essentially, remove the then to avoid JS treating it as a then-able (which will cause it to never resolve, because it resolves to itself in a loop forever), then constructing my own promise.