45 lines
1.4 KiB
TypeScript
45 lines
1.4 KiB
TypeScript
// Copyright 2021 Signal Messenger, LLC
|
|
// SPDX-License-Identifier: AGPL-3.0-only
|
|
|
|
import * as durations from './durations';
|
|
|
|
const BACKOFF_FACTOR = 1.9;
|
|
const MAX_BACKOFF = 15 * durations.MINUTE;
|
|
|
|
/**
|
|
* For a given attempt, how long should we sleep (in milliseconds)?
|
|
*
|
|
* The attempt should be a positive integer, and it is 1-indexed. The first attempt is 1,
|
|
* the second is 2, and so on.
|
|
*
|
|
* This is modified from [iOS's codebase][0].
|
|
*
|
|
* [0]: https://github.com/signalapp/Signal-iOS/blob/6069741602421744edfb59923d2fb3a66b1b23c1/SignalServiceKit/src/Util/OWSOperation.swift
|
|
*/
|
|
export function exponentialBackoffSleepTime(attempt: number): number {
|
|
const failureCount = attempt - 1;
|
|
if (failureCount === 0) {
|
|
return 0;
|
|
}
|
|
return Math.min(MAX_BACKOFF, 100 * BACKOFF_FACTOR ** failureCount);
|
|
}
|
|
|
|
/**
|
|
* If I want to retry for X milliseconds, how many attempts is that, roughly? For example,
|
|
* 24 hours (86,400,000 milliseconds) is 111 attempts.
|
|
*
|
|
* `desiredDurationMs` should be at least 1.
|
|
*/
|
|
export function exponentialBackoffMaxAttempts(
|
|
desiredDurationMs: number
|
|
): number {
|
|
let attempts = 0;
|
|
let total = 0;
|
|
// There's probably some algebra we could do here instead of this loop, but this is
|
|
// fast even for giant numbers, and is typically called just once at startup.
|
|
do {
|
|
attempts += 1;
|
|
total += exponentialBackoffSleepTime(attempts);
|
|
} while (total < desiredDurationMs);
|
|
return attempts;
|
|
}
|