improve http request response time - node.js

Question

I've created a nodejs script that make HTTP requests every 50ms, but it takes too long to receive response as request number grows.
how can I improve response time?
function makeRequest() {
superagent
.post('http://example.com')
.send({"test": "test"})
.set('Connection', 'keep-alive')
.then(console.log, console.log);
}
setInterval(() => makeRequest(), 50);

Answer 1

This is troublesome code. If your http request takes longer than 50ms to complete, then the number of active requests in flight will get larger and larger until eventually, you will consume too many system resources (sockets, memory, etc...). Things may get slower and slower or you may actually exhaust some resource and start to get errors or crash.
In addition, you don't want to be hitting the target server with thousands of simultaneous requests as it may also slow down under that type of load. This type of issue can also lead to an avalanche failure where a slight delay in the responsiveness of the response causes sudden build-up of requests which slows down the target server which leads to more build-up which quickly gets out of control and something dies. It's important to always code these types of things to avoid any sort of avalanche failure.
What I would suggest is making a new request some fixed number of ms from completion of the previous request (so there is only one request at a time in flight). Or a more complicated version would make a new request 50ms from when the previous one started, but not before the previous one finishes. This way, you'd only ever have one request in flight at a time and they would never build-up and accumulate and resource usage should stay fairly constant, not building over time, even if the target server gets slow for some reason.
Here's a way to make the next request after the completion of the previous request and no more often than once every 50ms:
function makeRequest() {
return superagent
.post('http://example.com')
.send({ "test": "test" })
.set('Connection', 'keep-alive');
}
function delay(t) {
return new Promise(resolve => {
setTimeout(resolve, t);
});
}
function run() {
const repeatTime = 50;
const startTime = Date.now();
return makeRequest().catch(err => {
console.log(err);
// decide here if you want to keep going or not
// if so, then just return
// if not, then throw
}).then(result => {
console.log(result);
let delta = Date.now() - startTime;
if (delta < repeatTime) {
// wait until at least repeatTime has passed before starting next request
return delay(repeatTime - delta).then(run);
} else {
return run();
}
}).catch(() => {
// aborted because of error
});
}
run();