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| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 | 1x 6x 3x 3x 3x 3x 3x 29x 6x 6x 6x 6x 3x 3x 6x 29x 29x 29x 29x | import { sleep } from 'simple';
const DEFAULT_CONFIG = {
batchSize: 100,
delay: 0,
log: (...args) => console.log(...args)
};
// throttles the number of promises a promise generating function can execute. This is useful
// when you are firing off a large number of promises without waiting for them to be complete.
//
// the decorator maintains a count of the number of executions, and if the count hits a defined
// batch size, it blocks all subsequent promises until the current batch of promises complete.
export default function throttled(asyncFn, config) {
let count = 0;
let waitChain = Promise.resolve();
let promiseQueue = [];
config = {
...DEFAULT_CONFIG,
...(config || {})
};
return (...args) => {
if (count % config.batchSize === 0) {
// replaces the current wait chain with a Promise
// that waits for the current set of Promises to complete
// first before allowing any more promises to execute
//
// awkward, because of the mutable aspect of promiseQueue
// and count, we use an immediately executing function
// block where they do not mutate.
waitChain = (
(queue, count) =>
waitChain.then(() => {
config.log(`Completed ${count}`);
if (config.delay === 0) {
return Promise.all(queue);
} else {
return Promise.all(queue).then(sleep.bind(null, config.delay));
}
})
)(promiseQueue, count);
promiseQueue = [];
}
// we always return the tail.
const tail = waitChain.then(() => asyncFn(...args));
promiseQueue.push(tail);
count += 1;
return tail;
}
}
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