82 lines
2.8 KiB
TypeScript
82 lines
2.8 KiB
TypeScript
/*
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* Copyright (C) 2026 Fluxer Contributors
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*
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* This file is part of Fluxer.
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*
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* Fluxer is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Fluxer is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Affero General Public License for more details.
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*
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* You should have received a copy of the GNU Affero General Public License
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* along with Fluxer. If not, see <https://www.gnu.org/licenses/>.
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*/
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export interface ExponentialBackoffPolicy {
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baseSeconds: number;
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minimumSeconds: number;
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maximumSeconds: number;
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maxExponent: number;
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}
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export interface ExponentialBackoffInput {
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attemptCount: number;
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policy?: ExponentialBackoffPolicy;
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}
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export const DefaultExponentialBackoffPolicy: ExponentialBackoffPolicy = {
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baseSeconds: 1,
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minimumSeconds: 1,
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maximumSeconds: 600,
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maxExponent: 30,
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};
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function normalizeAttemptCount(attemptCount: number): number {
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if (!Number.isFinite(attemptCount)) {
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return 0;
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}
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return Math.max(0, Math.floor(attemptCount));
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}
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function validateExponentialBackoffPolicy(policy: ExponentialBackoffPolicy): void {
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if (!Number.isFinite(policy.baseSeconds) || policy.baseSeconds <= 0) {
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throw new Error(`Invalid exponential backoff baseSeconds: ${policy.baseSeconds}`);
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}
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if (!Number.isFinite(policy.minimumSeconds) || policy.minimumSeconds <= 0) {
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throw new Error(`Invalid exponential backoff minimumSeconds: ${policy.minimumSeconds}`);
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}
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if (!Number.isFinite(policy.maximumSeconds) || policy.maximumSeconds <= 0) {
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throw new Error(`Invalid exponential backoff maximumSeconds: ${policy.maximumSeconds}`);
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}
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if (policy.maximumSeconds < policy.minimumSeconds) {
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throw new Error(
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`Invalid exponential backoff policy: maximumSeconds(${policy.maximumSeconds}) is smaller than minimumSeconds(${policy.minimumSeconds})`,
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);
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}
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if (!Number.isFinite(policy.maxExponent) || policy.maxExponent < 0) {
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throw new Error(`Invalid exponential backoff maxExponent: ${policy.maxExponent}`);
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}
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}
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export function computeExponentialBackoffSeconds(input: ExponentialBackoffInput): number {
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const policy = input.policy ?? DefaultExponentialBackoffPolicy;
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validateExponentialBackoffPolicy(policy);
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const normalizedAttemptCount = normalizeAttemptCount(input.attemptCount);
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const exponent = Math.min(normalizedAttemptCount, Math.floor(policy.maxExponent));
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const backoffSeconds = policy.baseSeconds * 2 ** exponent;
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const cappedBackoffSeconds = Math.min(backoffSeconds, policy.maximumSeconds);
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return Math.max(cappedBackoffSeconds, policy.minimumSeconds);
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}
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