froatsnook / meteor-sleep

Fiber-friendly/async sleep statements

Fiber-friendly/async sleep statements

Example

console.assert(Meteor.isServer); // Meteor.sleep (without ES7) only works on the server
Meteor.sleep(1000); // ms

console.assert(Meteor.isServer); // Meteor.sleepUntil (without ES7) only works on the server
Meteor.sleepUntil(new Date(2020, 3, 1));

Why?

Meteor's fibers let you wait (i.e. during I/O) without blocking the event loop. But the greatest of all ways to wait has been unattainable until now. This package lets you sprinkle sleep statements throughout your code to convince your boss to buy better hardware. Or to rate-limit your API usage without using setTimeout.

// Shopify wants no more than two events per second.
var results = [];
for (var i = 0; i < numPages; i++) {
    Meteor.sleep(500);

    var currentPage = FetchOrders(i);
    results = results.concat(currentPage);
}
HandleResults(results);

Now with ES7 support

Have you ever wondered what the best ES7 feature is? Well, the answer is async/await. Here's why:

console.assert(Meteor.isClient); // Meteor.sleep works on the client with ES7
async function() {
    // Do stuff

    // Sleep 2 seconds
    await Meteor.sleep(2000);

    // Sleep for days
    await Meteor.sleepUntil(new Date(2020, 3, 1));

    // Do other stuff
}

In other words, Meteor.sleep also works on the client now. This won't actually work until Meteor 1.3, but prepare yourself.

In a future version it should be possible to use await Meteor.sleep() on the server for a truly isomorphic experience.

Alternatives

The real advantage is code clarity. The following examples demonstrate how this code might be written in the browser (where fibers are not available).

// plain javascript
var results = [];
(function fetcher(i) {
    if (i === 5) {
        HandleResults(results);
        return;
    }

    var currentPage = FetchOrders(i);
    results = results.concat(currentPage);
    Meteor.setTimeout(function() {
        fetcher(i + 1);
    }, 500);
})(0);

// async.js
async.concatSeries(_.range(5), function(i, callback) {
    var currentPage = FetchOrders(i);
    Meteor.setTimeout(function() {
        callback(null, currentPage);
    }, 500);
}, function(err, results) {
    HandleResults(results);
});

Setup

• Install meteor add froatsnook:sleep

License

MIT