Heroku 503 Service Unavailable

Question

I am currently building a simple CRUD app using ExpressJS, and host it on Heroku using free account.

The problem I ran into is:

• GET API for getting all items works on localhost, but show status 503 when hosting on Heroku;
• POST API for updating one item works on localhost, but same issue as GET API above;
• All 503 errors are after 30s of loading, this should be a setting from Heroku.

I do have other API end points that work on both local and Heroku server:

• GET API for getting one item using ID

My guessing:

• The issue should not be a code issue
• There is some issue when the code is deployed and Heroku cannot process this request

I tried to find some articles on the web but this seems hard to diagnose, anyone who has experience please let me know how I can solve this issue. Appreciate your comments.

My Mongoose Schema

const mongoose = require("mongoose");

const ThoughtSchema = mongoose.Schema({
  title: {
    type: String,
    required: true
  },
  content: {
    type: String,
    required: true
  },
  date: {
    type: Date,
    default: Date.now
  }
});

module.exports = mongoose.model("Thought", ThoughtSchema);

2 end points that do not work

// Returns all thoughts
router.get("/", async (req, res) => {
  try {
    const thought = await Thought.find();
    res.json(thought);
  } catch (err) {
    res.json({ message: err });
  }
});

// Submit a post
router.post("/", async (req, res) => {
  const thought = new Thought({
    title: req.body.title,
    content: req.body.content
  });

  try {
    const savedThought = await thought.save();
    res.json(savedThought);
  } catch (err) {
    res.json({ message: err });
  }
});

The end point that works

// Specific thought
router.get("/:thoughtId", async (req, res) => {
  try {
    const thought = await Thought.findById(req.params.thoughtId);
    res.json(thought);
  } catch (err) {
    res.json({ message: err });
  }
});

My package.json for this express app

{
  "name": "my-thoughts-app",
  "version": "0.1.0",
  "description": "An app to records user's thoughts",
  "main": "index.js",
  "scripts": {
    "start": "node index.js",
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "repository": {
    "type": "git",
    "url": "git+https://github.com/PayneTang/my-thoughts-app.git"
  },
  "author": "Payne Tang",
  "license": "ISC",
  "bugs": {
    "url": "https://github.com/PayneTang/my-thoughts-app/issues"
  },
  "homepage": "https://github.com/PayneTang/my-thoughts-app#readme",
  "dependencies": {
    "dotenv": "^8.2.0",
    "express": "^4.17.1",
    "mongoose": "^5.8.11"
  },
  "devDependencies": {
    "typescript": "^3.7.5"
  }
}

EDIT: My index.js

const express = require("express");
const path = require("path");
const app = express();
const mongoose = require("mongoose");
const thoughtRoute = require("./routes/thought");
require("dotenv").config();

console.log(process.env);

// Mongoose settings
mongoose.connect(
  process.env.DB_CONNECTION,
  { useNewUrlParser: true, useUnifiedTopology: true },
  () => {
    console.log("Connected to DB!");
  }
);

app.use(express.json());
app.use((req, res, next) => {
  res.header("Access-Control-Allow-Origin", "*");
  res.header("Access-Control-Allow-Methods", "*");
  res.header(
    "Access-Control-Allow-Headers",
    "Origin, X-Requested-With, Content-Type, Accept"
  );
  next();
});

app.use("/api/thought", thoughtRoute);
app.get("/api/test", (req, res) => {
  res.send("hi");
});

// Serve client side
app.use(express.static(path.join(__dirname, "client/build")));
app.use(express.static(path.join(__dirname, "client/public")));
// app.get("*", (req, res) => {
//   res.sendFile(path.join(__dirname, "client/build/index.html"));
// });

const PORT = process.env.PORT || 5000;
app.listen(PORT, () => {
  console.log("Listening on port " + PORT + "...");
});

Answer 1

The root cause after checking is due to the access restriction from Heroku to Mongo atlas.

After adding 0.0.0.0/0 for IP whitelist, I am able to get data from MongoDB.

Reference: https://docs.atlas.mongodb.com/security-whitelist/#add-whitelist-entries