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import {isAbortError, catchAbortError} from './AbortError'; | ||
import {delay} from './delay'; | ||
import {execute} from './execute'; | ||
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export type ProactiveRetryOptions = { | ||
/** | ||
* Base delay between attempts in milliseconds. | ||
* | ||
* Defaults to 1000. | ||
* | ||
* Example: if `baseMs` is 100, then retries will be attempted in 100ms, | ||
* 200ms, 400ms etc (not counting jitter). | ||
*/ | ||
baseMs?: number; | ||
/** | ||
* Maximum for the total number of attempts. | ||
* | ||
* Defaults to `Infinity`. | ||
*/ | ||
maxAttempts?: number; | ||
/** | ||
* Called after each failed attempt. | ||
* | ||
* Rethrow error from this callback to prevent further retries. | ||
*/ | ||
onError?: (error: unknown, attempt: number) => void; | ||
}; | ||
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/** | ||
* Proactively retry a function with exponential backoff. | ||
* | ||
* Also known as hedging. | ||
* | ||
* The function will be called multiple times in parallel until it succeeds, in | ||
* which case all the other calls will be aborted. | ||
*/ | ||
export function proactiveRetry<T>( | ||
signal: AbortSignal, | ||
fn: (signal: AbortSignal, attempt: number) => Promise<T>, | ||
options: ProactiveRetryOptions = {}, | ||
): Promise<T> { | ||
const {baseMs = 1000, onError, maxAttempts = Infinity} = options; | ||
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return execute(signal, (resolve, reject) => { | ||
const innerAbortController = new AbortController(); | ||
let attemptsExhausted = false; | ||
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const promises = new Map</* attempt */ number, Promise<T>>(); | ||
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function handleFulfilled(value: T) { | ||
innerAbortController.abort(); | ||
promises.clear(); | ||
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resolve(value); | ||
} | ||
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function handleRejected(err: unknown, attempt: number) { | ||
promises.delete(attempt); | ||
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if (attemptsExhausted && promises.size === 0) { | ||
reject(err); | ||
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return; | ||
} | ||
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if (isAbortError(err)) { | ||
return; | ||
} | ||
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if (onError) { | ||
try { | ||
onError(err, attempt); | ||
} catch (err) { | ||
innerAbortController.abort(); | ||
promises.clear(); | ||
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reject(err); | ||
} | ||
} | ||
} | ||
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async function makeAttempts(signal: AbortSignal) { | ||
for (let attempt = 0; ; attempt++) { | ||
const promise = fn(signal, attempt); | ||
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promises.set(attempt, promise); | ||
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promise.then(handleFulfilled, err => handleRejected(err, attempt)); | ||
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if (attempt + 1 >= maxAttempts) { | ||
break; | ||
} | ||
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// https://aws.amazon.com/ru/blogs/architecture/exponential-backoff-and-jitter/ | ||
const backoff = Math.pow(2, attempt) * baseMs; | ||
const delayMs = Math.round((backoff * (1 + Math.random())) / 2); | ||
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await delay(signal, delayMs); | ||
} | ||
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attemptsExhausted = true; | ||
} | ||
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makeAttempts(innerAbortController.signal).catch(catchAbortError); | ||
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return () => { | ||
innerAbortController.abort(); | ||
}; | ||
}); | ||
} |