Node.js http.request keepAlive

Question

I'm trying to use http.Agent({ keepAlive: true}) on http.request to keep the connection open for future requests.

I created a simple server to log each new connection but when i run my request.js the server logs two new connections.

How can i use the HTTP keep-alive with Node.js native modules?

request.js:

const http = require("http");

const agent = new http.Agent({
    keepAlive: true
});

var req1 = http.request({
    agent: agent,
    method: "GET",
    hostname: "localhost",
    port: 3000
}, function (res1) {
    console.log("REQUEST_1");

    var req2 = http.request({
        agent: agent,
        method: "GET",
        hostname: "localhost",
        port: 3000
    }, function (res2) {
        console.log("REQUEST_2");
    });

    req2.end();
});

req1.end();

server.js:

const http = require('http');

var server = http.createServer(function (req, res) {
    res.end('OK');
    console.log("REQUEST");
})

server.on('connection', function (socket) {
    console.log("NEW CONNECTION");
})

server.listen(3000);

output:

NEW CONNECTION
REQUEST
NEW CONNECTION
REQUEST

kuba · Accepted Answer · 2019-05-22 12:55:51Z

6

Set maxSockets options like this:

const agent = new http.Agent({
    keepAlive: true,
    maxSockets: 1
});

By default maxSockets is set to Infinity - https://nodejs.org/api/http.html#http_new_agent_options

Full example on node v10

const http = require("http");

const agent = new http.Agent({
    keepAlive: true,
    maxSockets: 1
});

var req1 = http.request({
    agent: agent,
    method: "GET",
    hostname: "localhost",
    port: 3000
}, function (res1) {
    console.log("REQUEST_1");

    res1.on('data', function () {
        console.log("REQUEST_1 data");
    });

    res1.on('end', function () {
        console.log("REQUEST_1 end");
    });

    var req2 = http.request({
        agent: agent,
        method: "GET",
        hostname: "localhost",
        port: 3000
    }, function (res2) {
        console.log("REQUEST_2");

        res2.on('data', function () {
            console.log("REQUEST_2 data");
        });

        res2.on('end', function () {
            console.log("REQUEST_2 end");
        });
    });
    req2.end();
});
req1.end();

edited May 22, 2019 at 12:55

answered May 22, 2019 at 12:12

kuba

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4 Comments

isflavior Over a year ago

I got the same result, however now the "REQUEST_2" was delayed. It seems like the second request is waiting for the first one to close.

isflavior Over a year ago

Thanks. Now its working, i was not handling the events ''data' and 'end' of the requests.

Andrea Franchini Over a year ago

Why it doesn't work without handling (even a 'noop' is fine) the events 'data' and 'end' of the requests?

kuba Over a year ago

The explenation is here: nodejs.org/dist/latest-v10.x/docs/api/… , starts with "If no 'response' handler is added". You can omit end event in this case but I've added this to cover it all.

Stanley Ulili · Accepted Answer · 2024-09-26 07:33:56Z

5

Starting with Node.js v19, the keepAlive option is set to true by default for all outgoing HTTP(s)/1.1 connections.

You can read more about it on Node.js's v19 documentation.

edited Sep 26, 2024 at 7:33

answered Dec 23, 2022 at 14:50

Stanley Ulili

1,64216 silver badges18 bronze badges

2 Comments

Martin Luther ETOUMAN NDAMBWE Over a year ago

Thank you @Stanley. they say for "HTTP(S)/1.1". Do you know if this also applies to HTTPS/2 ?

Stanley Ulili Over a year ago

I haven't seen anything in the documentation indicating that it also applies to HTTP(S)/2. I’ve updated the answer to clarify that—thanks for the question!

lucaswxp · Accepted Answer · 2020-07-30 18:57:49Z

0

The accepted answer doesn't make clear that the code posted will allow only one request simultaneously per host per thread.

That is usually not what you want and will lead to requests slowing down waiting for the previous one to complete.

answered Jul 30, 2020 at 18:57

lucaswxp

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1 Comment

mactyr Over a year ago

This is a helpful clarification, but it should really be a comment on the other answer, not an answer of its own. By itself, it does not answer the question.

Xt Z · Accepted Answer · 2022-12-30 09:53:24Z

0

your demo not set res1's on data listener ,it will cause the socket not be close ,so the second request have to create a new connect to server ,just add a data listener

answered Dec 30, 2022 at 9:53

Xt Z

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