Queue endpoint

index.js

const express = require("express");
const app = express();
const queue = require("./queue");

app.get("/stats", (req, res) => {
  res.send(JSON.stringify(queue.dump()));
});

app.get("/enqueue", (req, res) => {
  const message = req.query.message;
  queue.enqueue(message);
  res.send("message queued = " + message);
});

app.get("/dequeue", (req, res) => {
  const m = queue.dequeue();
  if (m) {
    res.send("message is = " + m.message);
  } else {
    res.send("no message in queue");
  }
});

app.listen(3000, () => {
  console.log("Server is running on port 3000");
});

queue.js

const queue = [];
const deadQueue = [];
const processMap = {};

const RETRY_TIMEOUT = 3000; // in ms

let id = 1;

module.exports = {
  enqueue(message) {
    if (typeof message == "string") {
      message = { message, id: id++ };
    }
    processMap[message.id] = (processMap[message.id] || 0) + 1;

    if (processMap[message.id] > 3) {
      deadQueue.push(message);
      return;
    }
    queue.push(message);
  },

  dequeue() {
    const m = queue.shift();
    if (m) {
      this.process(m);
      return m;
    }
    return null;
  },

  process(m) {
    setTimeout(this.enqueue.bind(this, m), RETRY_TIMEOUT);
  },

  dump() {
    return {
      queue,
      deadQueue,
    };
  },
};