HTTP keep-alive in node.js

I am trying to set-up a HTTP client to keep the underlying connection open (keep-alive) in node.js, but it seems that the behaviour does not correspond to the docs ().

I am creating a new HTTP agent, setting the maxSockets property to 1 and requesting an url (for instance ) every second.

It seems that on every request the socket is closed and a new socket is created. I have tested this with node.js 0.10.25 and 0.10.36 under Ubuntu 14.04.

Has anyone been able to get keep alive to work?

Here is the code:

var http = require("http");
var agent = new http.Agent();
agent.maxSockets = 1;
var sockets = [];
function request(hostname, path, callback) { var options = { hostname: hostname, path: path, agent: agent, headers: {"Connection": "keep-alive"} }; var req = http.get(options, function(res) { res.setEncoding('utf8'); var body = ""; res.on('data', function (chunk) { body += chunk; }); res.on('end', function () { callback(null, res, body); }); }); req.on('error', function(e) { return callback(error); }); req.on("socket", function (socket) { if (sockets.indexOf(socket) === -1) { console.log("new socket created"); sockets.push(socket); socket.on("close", function() { console.log("socket has been closed"); }); } });
}
function run() { request(' '/', function (error, res, body) { setTimeout(run, 1000); });
}
run();

3 Answers

If I'm not mistaken the connection pool was implemented in 0.12.

So if you want to have a connection pool prior 0.12 you can simply use the request module:

var request = require('request')
request.get(' {forever: true}, function (err, res, body) {});

If you are using node 0.12+ and you want to use the HTTP core module directly, then you can use this to initialize your agent:

var agent = new http.Agent({ keepAlive: true, maxSockets: 1, keepAliveMsecs: 3000
})

Notice the keepAlive: true property, that is required to keep the socket open.

You can pass an agent to the request module as well, again that works only on 0.12+ otherwise it defaults to internal pool implementation.

I guess it should work on node 0.12+. You may also want to use a different agent for this purpose. For example keep-alive-agent can do what you want:

var KeepAliveAgent = require('keep-alive-agent'), agent = new KeepAliveAgent();

The below worked for me in meteor which uses the npm module for keepaliveagent

var agent = new KeepAliveAgent({ maxSockets: 1 });
var options = { agent:agent, headers: {"Connection":"Keep-Alive"}
}
try { var client = Soap.createClient(url); var result = client.myfirstfunction(args,options);
//process result result = client.mysecondfunction(args,options);
}

Both the method calls returns data in one socket connection. You pass the options in each method call