75 lines
2.2 KiB
Markdown
75 lines
2.2 KiB
Markdown
# throat
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Throttle the parallelism of an asynchronous, promise returning, function / functions. This has special utility when you set the concurrency to `1`. That way you get a mutually exclusive lock.
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[](https://travis-ci.org/ForbesLindesay/throat)
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[](https://coveralls.io/r/ForbesLindesay/throat?branch=master)
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[](https://gemnasium.com/ForbesLindesay/throat)
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[](http://badge.fury.io/js/throat)
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[](https://saucelabs.com/u/throat)
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## Installation
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npm install throat
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## API
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### throat(concurrency)
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This returns a function that acts a bit like a lock (exactly as a lock if concurrency is 1).
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Example, only 2 of the following functions will execute at any one time:
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```js
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// with polyfill or in iojs
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require('promise/polyfill')
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var throat = require('throat')(2)
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// alternatively provide your own promise implementation
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var throat = require('throat')(require('promise'))(2)
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var resA = throat(function () {
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//async stuff
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return promise
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})
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var resA = throat(function () {
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//async stuff
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return promise
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})
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var resA = throat(function () {
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//async stuff
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return promise
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})
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var resA = throat(function () {
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//async stuff
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return promise
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})
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var resA = throat(function () {
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//async stuff
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return promise
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})
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```
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### throat(concurrency, worker)
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This returns a function that is an exact copy of `worker` except that it will only execute up to `concurrency` times in parallel before further requests are queued:
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```js
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// with polyfill or in iojs
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require('promise/polyfill')
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var throat = require('throat')
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// alternatively provide your own promise implementation
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var throat = require('throat')(require('promise'))
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var input = ['fileA.txt', 'fileB.txt', 'fileC.txt', 'fileD.txt']
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var data = Promise.all(input.map(throat(2, function (fileName) {
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return readFile(fileName)
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})))
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```
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Only 2 files will be read at a time, sometimes limiting parallelism in this way can improve scalability.
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## License
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MIT
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