superagent-throttle

A plugin for superagent that throttles requests. Useful for rate or concurrency limited APIs.

Features

• This doesn't just delay requests by an arbitrary number of ms, but intelligently manages requests so they're sent as soon as possible whilst staying beneath rate limits.
• Can make serialised subqueues on the fly.
• Follows superagent .use(throttle.plugin()) architecture
• Hackable
• Can use multiple instances

Install

  npm i --save superagent-throttle

Basic Usage

const request     = require('superagent')
const _           = require('underscore')
const Throttle    = require('superagent-throttle')

let throttle = new Throttle({
  active: true,     // set false to pause queue
  rate: 5,          // how many requests can be sent every `ratePer`
  ratePer: 10000,   // number of ms in which `rate` requests may be sent
  concurrent: 2     // how many requests can be sent concurrently
})

_.each(_.range(1, 15), function(iteration) {
  let width = 100 + iteration
  request
  .get('http://placekitten.com/' + width + '/100')
  .use(throttle.plugin())
  .end(function(err, res) {
    console.log(err ? err : 'retrieved ' + iteration)
  })
  console.log('added ' + iteration)
})

Serialised Sub Queues

When using API's to update a client, you may want some serialised requests which still count towards your rate limit, but do not block other requests. You can do that by passing a uri (not necessarily a valid url) to throttle.plugin, for those requests you want to serialise, and leave it out for other async requests. This can be done on the fly, you don't need to initialise subqueues first.

let endpoint = 'http://example.com/endpoint'
request
.get(endpoint)
.set('someData': someData)
.use(throttle.plugin(endpoint))
.end(callback)

it's common to use an endpoint for the uri, simply to serialise requests to that endpoint without interfering with requests to other endpoints

Options

• active: whether or not the queue is paused.
• rate: how many requests can be sent every ratePer
• ratePer: number of ms in which rate requests may be sent
• concurrent: how many requests can be sent concurrently

Options can be set after instantiation using the set method.

    var throttle = new require('./index')({ active: false }) // start paused
    throttle.set('active', true) // unpause

Advanced Usage

See theMovieDbApi

Api

See the fancy annotated code.

Author

Levi Wheatcroft levi@wht.cr

Contributing

Contributions welcome; Please submit all pull requests against the master branch.

License

• MIT : http://opensource.org/licenses/MIT