Run multiple promise-returning & async functions with limited concurrency by key. The package maintains a mapping of p-limit object per key, so when the limit is called with the same key the promises' execution will be limited (following the concurrency value) but when used with different keys the promises' execution will not limit each other. The package automatically deletes the p-limit objects when they are no longer needed.

$ npm install p-key-limit

const myDbWrapper = require('./my-db-wrapper'); // assumes to have an async function called getInfo.
const pKeyLimit = require('p-key-limit');

const limit = pKeyLimit(5);

// Each user gets its own "p-limit" queue and can execute 5 parallel info requests.
function getInfoForUser(userId, infoKey) {
    if (limit.getSize(userId) > 20) {
        // user is overflowing with requests!
        throw new Error("That's too much, man!");
    }
    return limit(userId, () => myDbWrapper.getInfo(infoKey))
}

Returns a limit function.

Type: number
Minimum: 1

Concurrency limit.

Returns the promise returned by calling fn(...args).

Type: Function

Promise-returning/async function.

Any arguments to pass through to fn.

Support for passing arguments on to the fn is provided in order to be able to avoid creating unnecessary closures. You probably don't need this optimization unless you're pushing a lot of functions.

Returns the number of promises that are currently running for the given key plus the number of promises that are currently queued for the given key. Useful to detect overflows.

• p-limit - Run multiple promise-returning & async functions with limited concurrency

MIT © Oren Zomer