Error on deploying mongodb and express project-CodePudding

I'm deploying my express app which has mongoose connection. On localhost everything working perfectly. But when I deploy to heroku, I'm getting an error "Application error" with status 503.

When I tried to deploy without mongoose connection my application was working on heroku server perfectly. So I got that problem might be on mongoose connection.

index.js mongoose connection part of code (not working on heroku):

app.get("/", (req, res) => {
  res.send(`Server launched perfectly!`);
});

const PORT = process.env.PORT || 5000;

mongoose.connect(process.env.CONNECTION_URL, { useNewUrlParser: true, useUnifiedTopology: true })
  .then(() => app.listen(PORT, () => console.log(`Server Running on Port: http://localhost:${PORT}`)))
  .catch((error) => console.log(`${error} did not connect`));

mongoose.connect(process.env.CONNECTION_URL).then(()=>{console.log('...')});

index.js without mongoose connection (working perfectly on heroku):

app.get("/", (req, res) => {
  res.send(`Server launched perfectly!`);
});

const PORT = process.env.PORT || 5000;

app.listen(PORT, () => console.log(`Server Running on Port: http://localhost:${PORT}`));

It might be a different problem, but Procfile and package.json are fine.

CodePudding user response：

The connection should be asynchronous, you can create a function like this:

const connect = async () => {
    try {
        const db = await mongoose.connect(DB_URL, {
            useUnifiedTopology: true,
            useNewUrlParser: true,
            useFindAndModify: false
        });
        
        const { name, host } = db.connection;
        console.log(`Conección correcta a la base de datos ${name} en ${host}`);
    } catch(error) {
        console.log('Problemas al conectarse a la DB. Error ->', error);
    }
};