Zaid Humaimidi
c3954c277f
Separated cwmp and ui code into distinct files to enhance clarity and maintainability with varied internal data representations.
92 lines
2.6 KiB
TypeScript
92 lines
2.6 KiB
TypeScript
/**
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* Copyright 2013-2019 GenieACS Inc.
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*
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* This file is part of GenieACS.
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*
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* GenieACS 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
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* published by the Free Software Foundation, either version 3 of the
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* License, or (at your option) any later version.
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*
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* GenieACS 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 GenieACS. If not, see <http://www.gnu.org/licenses/>.
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*/
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import { setTimeoutPromise } from "./util";
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import { acquireLock, get, releaseLock, set } from "./cache";
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const REFRESH = 5000;
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const EVICT_TIMEOUT = 120000;
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export class LocalCache<T> {
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private nextRefresh = 1;
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private currentRevision: string = null;
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private snapshots: Map<string, T> = new Map();
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constructor(
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private cacheKey: string,
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private callback: () => Promise<[string, T]>
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) {}
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async getRevision(): Promise<string> {
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if (Date.now() > this.nextRefresh) await this.refresh();
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return this.currentRevision;
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}
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hasRevision(revision: string): boolean {
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return this.snapshots.has(revision);
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}
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get(revision: string): T {
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const snapshot = this.snapshots.get(revision);
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if (!snapshot) throw new Error("Cache snapshot does not exist");
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return snapshot;
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}
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async refresh(): Promise<void> {
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if (!this.nextRefresh) {
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await setTimeoutPromise(20);
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await this.refresh();
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return;
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}
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const now = Date.now();
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if (now < this.nextRefresh) return;
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this.nextRefresh = 0;
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const dbHash = await get(this.cacheKey);
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if (this.currentRevision && dbHash === this.currentRevision) {
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this.nextRefresh = now + (REFRESH - (now % REFRESH));
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return;
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}
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const lockToken = await acquireLock(this.cacheKey + "_lock", 5000);
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const [hash, snapshot] = await this.callback();
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if (this.currentRevision) {
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const r = this.currentRevision;
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const s = this.snapshots.get(r);
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setTimeout(() => {
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if (this.snapshots.get(r) === s) this.snapshots.delete(r);
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}, EVICT_TIMEOUT).unref();
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}
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this.currentRevision = hash;
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this.snapshots.set(hash, snapshot);
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if (lockToken) {
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if (hash !== dbHash) await set(this.cacheKey, hash, 300);
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await releaseLock(this.cacheKey + "_lock", lockToken);
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}
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this.nextRefresh = now + (REFRESH - (now % REFRESH));
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}
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}
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