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56 lines
2.3 KiB
56 lines
2.3 KiB
2 years ago
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# 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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[Professionally supported throat is now available](https://tidelift.com/subscription/pkg/npm-throat?utm_source=npm-throat&utm_medium=referral&utm_campaign=readme)
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[](https://github.com/ForbesLindesay/throat/actions?query=workflow%3ATest+branch%3Amaster)
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[](https://coveralls.io/github/ForbesLindesay/throat)
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[](https://rollingversions.com/ForbesLindesay/throat)
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[](https://www.npmjs.com/package/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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const throat = require('throat')(2);
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const resA = throat(async () => { /* async stuff... */ });
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const resB = throat(async () => { /* async stuff... */ });
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const resC = throat(async () => { /* async stuff... */ });
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const resD = throat(async () => { /* async stuff... */ });
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const resE = throat(async () => { /* async stuff... */ });
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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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const throat = require('throat');
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const input = ['fileA.txt', 'fileB.txt', 'fileC.txt', 'fileD.txt'];
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const data = Promise.all(
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input.map(throat(2, (fileName) => 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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## Security contact information
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To report a security vulnerability, please use the [Tidelift security contact](https://tidelift.com/security). Tidelift will coordinate the fix and disclosure.
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## License
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MIT
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