87 lines
2.9 KiB
TypeScript
87 lines
2.9 KiB
TypeScript
/*
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* Copyright 2025 coze-dev Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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import { sleep } from './async';
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type Fn<ARGS extends unknown[], Ret = unknown> = (...args: ARGS) => Ret;
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/**
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* 限流器，对于被限流的异步方法进行以下形式的限流：
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* 1. 在 timeWindow 内的前 limit 个请求不做限制，立即发送
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* 2. timeWindow 内超过 limit 个请求后，对每个请求依次添加 onLimitDelay 毫秒的延迟
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*
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* 注意是排队添加，形如 invoke: [1(0ms), 2(0ms), 3(0ms), 4(0ms)]; limit: [1(0ms), 2(0ms), 3(100ms), 4(200ms)]
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*
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* 另注：这个设计遭到了猛烈抨击，认为 debounce 可以代替掉，实现过于复杂，但是考虑：
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* 1. 支持列表双向加载的拉取，简单使用 debounce 可能导致请求某侧丢失；添加延时可以保证不丢失请求
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* 2. 列表拉取一旦出现死循环，可能导致恶性问题，如密集地对服务端接口的高频访问
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*
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* 以上场景通常不应出现，所以 limit 设计也只是对极端场景的兜底，上层 UI 错误理应得到妥善解决
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* TODO: wlt - 补充 testcase
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*/
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export class RateLimit<ARGS extends unknown[], Ret> {
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constructor(
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private fn: Fn<ARGS, Promise<Ret>>,
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private config: {
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onLimitDelay: number;
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limit: number;
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timeWindow: number;
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},
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) {}
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private records: number[] = [];
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private getNewInvokeDelay(): number {
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const { timeWindow, limit, onLimitDelay } = this.config;
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const now = Date.now();
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const windowEdge = now - timeWindow;
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const idx = this.records.findIndex(t => t >= windowEdge);
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if (idx < 0) {
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return 0;
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}
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const lasts = this.records.slice(idx);
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if (lasts.length < limit) {
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return 0;
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}
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const last = lasts.at(-1);
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if (!last) {
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return 0;
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}
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return last + onLimitDelay - now;
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}
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private clearRecords() {
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const { timeWindow } = this.config;
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const now = Date.now();
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const windowEdge = now - timeWindow;
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const idx = this.records.findLastIndex(t => t < windowEdge);
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if (idx >= 0) {
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this.records = this.records.slice(idx + 1);
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}
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}
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invoke = async (...args: ARGS): Promise<Ret> => {
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const invokeDelay = this.getNewInvokeDelay();
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const now = Date.now();
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this.records.push(invokeDelay + now);
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if (invokeDelay) {
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await sleep(invokeDelay);
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}
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this.clearRecords();
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return this.fn(...args);
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};
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}
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