lib/db.js


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import { sleep } from "$lib/utils";
import { createClient } from "redis";

export const db = createClient({ url: "redis://db" });
await db.connect();
export default db;

export let g = async k => JSON.parse(await db.get(k));
export let s = (k, v) => db.set(k, JSON.stringify(v));

let retries = {};
export let t = async (k, f) => {
  let result;
  try {
    result = await db.executeIsolated(async db => {
      await db.watch(k);
      let v = await db.get(k);
      await db
        .multi()
        .set(k, await f(v))
        .exec();
    });
  } catch (err) {
    if (!err.message.includes("watch")) throw err;

    let r = retries[k] || 0;
    retries[k] = r + 1;

    if (r < 10) {
      await sleep(100);
      await t(k, f);
    } else {
      delete retries[k];
      throw new Error("unable to obtain lock");
    }
  }

  delete retries[k];
  return result;
};