NodeJS - How to have express wait for a response? - node.js

Question

I am working with a very small piece of nodeJS code thats using express. The app receives a payload as a POST and sends it to another method which submits it to kafka. Once this happens, I need to return a response back to express so that it can close the connection based on the status (return a 200 response for example).
// producer.js
// Defined variables
var kafka = require('kafka-node'),
Producer = kafka.Producer;
module.exports = {
sendToProducer: function (payload) {
// Define our kafka settings
var client = new kafka.KafkaClient(),
producer = new Producer(client);
// On producer ready
producer.on('ready', function () {
// Send our payload to our topic
producer.send(payload, function (err, data) {
console.log(data);
// Return our response back to `app.js` so express can handle it.
});
});
// On producer error
producer.on('error', function (err) {
console.log('Producer Error', err)
})
}
};
// app.js
app.post('/payload', function (req, res) {
// Define our route
const payload = req.body;
const route = payload.route;
// Check to see if we have a route
if(!route){
logError('no route');
}
let mappedData = [{ topic: 'test', messages: 'hi... ', partition: 0 }]
// Based on the route
switch(route){
// Receive data
case 'ingest':
producer.sendToProducer(mappedData);
// How can I tell express the status of the above method so that we can close the request? (ex 200 response for example?)
break;
// Handle undefined routes
default:
break;
}
});
In my app.js case statement, how can I wait for a response/callback from producer.sendToProducer(mappedData); so that I can handle the express status appropriately ?

Answer 1

Make sure your sendToProducer() is a promise / async function :
app.post('/payload', async function (req, res) {
// Define our route
const payload = req.body;
const route = payload.route;
// Check to see if we have a route
if(!route){
logError('no route');
}
let mappedData = [{ topic: 'test', messages: 'hi... ', partition: 0 }]
// Based on the route
switch(route){
// Receive data
case 'ingest':
await producer.sendToProducer(mappedData);
// How can I tell express the status of the above method so that we can close the request? (ex 200 response for example?)
break;
// Handle undefined routes
default:
break;
}
});