51 lines
1.4 KiB
TypeScript
51 lines
1.4 KiB
TypeScript
import { collections } from "./db/db.ts";
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const CLOCK_SKEW_TOLERANCE = 30000;
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export async function acquireLock(
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lockName: string,
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ttl: number,
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timeout = 0,
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token = Math.random().toString(36).slice(2),
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): Promise<string> {
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try {
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const now = Date.now();
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const r = await collections.locks.findOneAndUpdate(
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{ _id: lockName, value: token },
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{
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$set: {
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expire: new Date(now + ttl + CLOCK_SKEW_TOLERANCE),
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},
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$currentDate: { timestamp: true },
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},
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{ upsert: true, returnDocument: "after" },
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);
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if (Math.abs(r.value.timestamp.getTime() - now) > CLOCK_SKEW_TOLERANCE)
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throw new Error("Database clock skew too great");
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} catch (err) {
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if (err.code !== 11000) throw err;
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if (!(timeout > 0)) return null;
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const w = 50 + Math.random() * 50;
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await new Promise((resolve) => setTimeout(resolve, w));
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return acquireLock(lockName, ttl, timeout - w, token);
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}
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return token;
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}
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export async function releaseLock(
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lockName: string,
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token: string,
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): Promise<void> {
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const res = await collections.locks.deleteOne({
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_id: lockName,
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value: token,
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});
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if (res.deletedCount !== 1) throw new Error("Lock expired");
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}
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export async function getToken(lockName: string): Promise<string> {
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const res = await collections.locks.findOne({ _id: lockName });
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return res?.value;
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}
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