file-lock.ts

import { writeFile } from "fs/promises";
import path from "path";
import lockFile from "proper-lockfile";
import { log } from "./logger";

export async function withFileLock<T>(fileName: string, fn: () => T): Promise<T> {
  const file = await createEmptyTmpFile(fileName);

  let releaseLockFn;
  try {
    log.debug(`Acquiring lock file "${file}"...`);
    releaseLockFn = await lockFile.lock(file, {
      retries: { forever: true, factor: 1, minTimeout: 500, maxTimeout: 3000, randomize: true },
    });
    log.debug(`Acquired lock file "${file}"`);
    return await fn();
  } finally {
    if (releaseLockFn) {
      log.debug(`Releasing lock file "${file}"...`);
      await releaseLockFn();
      log.debug(`Released lock file "${file}"`);
    }
  }
}

async function createEmptyTmpFile(fileName: string): Promise<string> {
  const tmp = await import("tmp");
  const file = path.resolve(tmp.tmpdir, fileName);
  try {
    await writeFile(file, "", { flag: "wx" });
  } catch (err) {
    const isExistError = err && typeof err === "object" && "code" in err && err.code === "EEXIST";
    if (!isExistError) {
      throw err;
    }
  }
  return file;
}