LimitMe

A library for limiting the rate of execution of callbacks and Promises

const RateLimiter = require('limitme');
const limiter = new RateLimiter(250); // one callback/Promise each 250ms
for(let i = 0; i < 10; i++) {
  limiter.enqueue()
           .then(() =>
             new Promise((resolve) => {
               console.log(`resolved Promise ${i}`);
               resolve();
             }));
  limiter.enqueue(() => {
    console.log(`Resolved Callback ${i}`)
  });
}

Installation

npm install limitme

Usage

First, require and instantiate LimitMe

const RateLimiter = require('limitme');
const limiter = new RateLimiter(msPerTask);

Where msPerTask is a variable specifying minimal delay between task executions.

Then... Use LimitMe!

limiter.enqueue().then((timeWaited) => new Promise());

Where new Promise() is your API request you needed to execute for example, and timeWaited is the time your task had to wait since creation to actual execution

You can also use callback-style if you want to:

limiter.enqueue((timeWaited) => {
  doYourTask(timeWaited);
})

Where doYourTask(timeWaited) is... Well, you guessed.

You may also use priorities:

limiter.enqueue(RateLimiter.priority.HIGHEST).then((timeWaited) => new Promise());

This will be executed before all HIGH, NORMAL, LOW and LOWEST priority tasks

Callback-style is supported as well, with similar syntax:

limiter.enqueue(RateLimiter.priority.HIGHEST, (timeWaited) => {
  doYourTask(timeWaited);
});

The priorities available are following:

RateLimiter.priority.HIGHEST,

RateLimiter.priority.HIGH,

RateLimiter.priority.NORMAL,

RateLimiter.priority.LOW,

RateLimiter.priority.LOWEST

Using an older node version which does not have Promises, or you would like to use your own Promise implementation, like bluebird? Just set the Promise property of RateLimiter object!

RateLimiter.Promise = require('bluebird'); // Wham, it now is on bluebird!

And lastly, you may also queue task for immediate execution (albeit this is not recommended), just replace enqueue with immediate, and the task will be pushed on top of HIGHEST priority queue.

If you want API, look below:

API

RateLimiter

RateLimiter is a root object that LimitMe exports. You need to instantiate it.

constructor(rateLimit)

• rateLimit - an integer specifying how often tasks should be fired, for example, when you want tasks to be fired every 250ms you call new RateLimiter(250)

Properties

• static priorities - used for setting priority of a specific task, for example to execute the task with highest priorty, you call RateLimiter.enqueue(RateLimiter.priorty.HIGHEST). LimitMe supports following priorities:
  • HIGHEST
  • HIGH
  • NORMAL
  • LOWEST
  • LOW
• static Promise - Promise implementation you wish to use. By default uses vanilla Node promises
• totalQueuedTasks - number of total tasks awaiting processing

Methods

The following methods are available for public:

• enqueue([priority, callback]) - is used to queue a task for execution. If you specify no parameters, this will return a promise, which will resolve when the task is allowed execution, if you specify callback, it will be called when you should proceed with your task (i.e. API request). Both the callback and the promise are resolved with time waited before execution/resolve in milliseconds
• runImmediate([callback]) - is used to queue the task for first possible time slot, and by that I mean that the task will be put on top of HIGHEST priority queue

Support

Please report bugs on the issue tracker