delayingRequestExecution_workerProcessCancelFunctions_taskQueue.js

function makeJobId (task) {
  const hash = crypto.createHash("md5");
  hash.update(JSON.stringify(task), "utf8");
  return hash.digest("hex");
}

/**
 * Registers `workerFn` as a function for adding and processing tasks.
 * The tasks are identified by workerFn's name property, so use named functions.
 *
 * @param {*} workerFn The function to register.
 * @returns
 */
function makeWorker (workerFn) {
  if (workerFn == null || typeof workerFn !== "function") {
    return null;
  }
  undoQueueWorkers.set(workerFn.name, workerFn);

  /**
   * Adds jobs to be processed by `workerFn`.
   *
   * @param {any[]} args Arguments to be passed to `workerFn`.
   * @returns {Promise<string|number>}
   */
  async function addJob (...args) {
    const task = {
      worker: workerFn.name,
      args
    };
    const jobId = makeJobId(task);
    const job = await queue.add(task, {
      jobId
    });
    return job.id;
  };

  return addJob;
}
exports.makeWorker = makeWorker;

/**
 * queueWorker receives jobs from the queue and calls the worker functions
 * that registered them to process them.
 *
 * @param {object} job The job to process
 * @returns {any} The return value of the worker function.
 */
async function queueWorker (job) {
  const workerFn = undoQueueWorkers.get(job.data.worker);
  if (workerFn == null) {
    const error = new Error(`No worker registered for job ${job.id}.`);
    error.data = `${job.data}`;
    throw error;
  }
  const args = job.data.args;
  const result = await workerFn(...args);
  return result;
}

// register queueWorker to process jobs from the queue
queue.process(queueWorker);

/**
 * Cancels the processing of a job waiting to be processed.
 * The job cannot be cancelled if it has already been, or is being, processed.
 *
 * @param {string|number} jobId The ID of the job to cancel
 * @returns {Promise<boolean>}
 */
async function cancelJob (jobId) {
  const job = await queue.getJob(jobId);
  if (job != null) {
    await job.remove();
    return true;
  }
  return false;
}
exports.cancelJob = cancelJob;