In Yaydoc, we use the user access token to do various tasks like pushing documentation, registering webhook and to see it’s status.The user access token is very important to us, so I decided of adding Cron job which checks whether the user token has expired or not. But then one problem was that, if we have more number of users our cron job will send thousands of request at a time so it can break the app. So, I thought of queueing the process. I used `asyc` library for queuing the job.

const github = require("./github")
const queue = require("./queue")

User = require("../model/user");

exports.checkExpiredToken = function () {
  User.count(function (error, count) {
    if (error) {
      console.log(error);
    } else {
      var page = 0;
      if (count < 10) {
        page = 1;
      } else {
        page = count / 10;
        if (page * 10 < count) {
          page = (count + 10) /10;
        }
      }
      for (var i = 0; i <= page; i++) {
        User.paginateUsers(i, 10,
        function (error, users) {
          if (error) {
            console.log(error);
          } else {
            users.forEach(function(user) {
              queue.addTokenRevokedJob(user);
            })
          }
        })
      }
    }
  })
}

In the above code I’m paginating the list of users in the database and then I’m adding each user to the queue.

var tokenRevokedQueue = async.queue(function (user, done) {
  github.retriveUser(user.token, function (error, userData) {
    if (error) {
      if (user.expired === false) {
        mailer.sendMailOnTokenFailure(user.email);
        User.updateUserById(user.id, {
          expired: true
        }, function(error, data) {
          if (error) {
            console.log(error);
          }
        });
      }
      done();
    } else {
      done();
    }
  })
}, 2);

I made this queue with the help of async queue method. In the first parameter, I’m passing the logic and in second parameter, I’m passing how many jobs can be executed asynchronously. I’m checking if the user has revoked the token or not by sending API requests to GitHub’s user API. If it gives a response ‘200’ then the token is valid otherwise it’s invalid. If the user token is invalid, I’m sending email to the user saying that “Your access token in revoked so Sign In once again to continue the service”.

Resources:

• Async JS Queue documentation – Caolan
• Introducing Queue In NodeJs – Pedro Teixeira
• Implementing Job Queue With Nodejs – Prateek Bhatt