bottleneck

Bottleneck is a simple and efficient Asynchronous Rate Limiter for Node.JS and the browser. When dealing with services with limited resources, it's important to ensure that they don't become overloaded. Bottleneck is the easiest solution as it doesn't add any complexity to the code.

Databases, file systems, network access, APIs, etc. are all services that can easily be overwhelmed.

#Install

Node

npm install bottleneck

Browser

<script type="text/javascript" src="bottleneck.min.js"></script>

#Example

Most APIs have a rate limit. For example, the Reddit.com API limits programs to 1 request every 2 seconds.

var Bottleneck = require("bottleneck"); //Node.JS only

// Wait at least 2000ms between each request.
// Never more than 1 request running at a time.
var limiter = new Bottleneck(1, 2000);

Instead of doing

someAsyncCall(arg1, arg2, argN, callback);

You now do

limiter.submit(someAsyncCall, arg1, arg2, argN, callback);

And now you can be assured that someAsyncCall will abide by your rate guidelines!

All the submitted requests will be executed in order.

#Docs

###Constructor new Bottleneck(maxNb, minTime, highWater, strategy);

• maxNb : How many requests can be running at the same time. Default: 0 (unlimited)
• minTime : How long to wait after launching a request before launching another one. Default: 0ms
• highWater : How long can the queue get? Default: 0 (unlimited)
• strategy : Which strategy use if the queue gets longer than the high water mark. Default: Bottleneck.strategy.LEAK.

###submit()

This adds a request to the queue.

It returns true if the queue's length is under the high water mark, otherwise it returns false.

If a callback isn't necessary, you must pass null instead.

###strategies

####Bottleneck.strategy.LEAK When submitting a new request, if the highWater mark is reached, drop the oldest request in the queue. This is useful when requests that have been waiting for too long are not important anymore.

####Bottleneck.strategy.OVERFLOW When submitting a new request, if the highWater mark is reached, do not add that request. The submit call did nothing.

###stopAll()

limiter.stopAll();

Cancels all queued up requests and prevents additonal requests from being submitted.

###changeSettings()

limiter.changeSettings(maxNb, minTime, highWater, strategy)

Same parameters as the constructor, pass null to skip a parameter and keep it to its current value.