http.get(url, cb) hangs after 5 requests on node v0.10.32

[hidekiy]

I found the strange behavior when I use http.get(url, cb) simply.

I verified this on Windows 7 / 8.1, CentOS 6.5 with official binary.

node v0.11.9 looks good.

I think this condition is insufficient:
https://github.com/joyent/node/blob/v0.10.32/lib/http.js#L1694-L1698

Test code is below:

var http = require('http');

http.createServer(function (req, res) {
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end('Hello World\n');
}).listen(2000);

var ix = 0;
setInterval(function () {
    http.get('http://localhost:2000/', function (r) {
        console.log({ix: ix++, status: r.statusCode});
        // the next line will resolve this problem:
        // r._dump();
    });
}, 200);

Output with NODE_DEBUG=http

HTTP: outgoing message end.
HTTP: SERVER new http connection
HTTP: write ret = true
HTTP: outgoing message end.
HTTP: AGENT incoming response!
HTTP: AGENT isHeadResponse false
{ ix: 0, status: 200 }
HTTP: outgoing message end.
HTTP: SERVER new http connection
HTTP: write ret = true
HTTP: outgoing message end.
HTTP: AGENT incoming response!
HTTP: AGENT isHeadResponse false
{ ix: 1, status: 200 }
HTTP: outgoing message end.
HTTP: SERVER new http connection
HTTP: write ret = true
HTTP: outgoing message end.
HTTP: AGENT incoming response!
HTTP: AGENT isHeadResponse false
{ ix: 2, status: 200 }
HTTP: outgoing message end.
HTTP: SERVER new http connection
HTTP: write ret = true
HTTP: outgoing message end.
HTTP: AGENT incoming response!
HTTP: AGENT isHeadResponse false
{ ix: 3, status: 200 }
HTTP: outgoing message end.
HTTP: SERVER new http connection
HTTP: write ret = true
HTTP: outgoing message end.
HTTP: AGENT incoming response!
HTTP: AGENT isHeadResponse false
{ ix: 4, status: 200 }
HTTP: outgoing message end.
HTTP: outgoing message end.
HTTP: outgoing message end.
HTTP: outgoing message end.
HTTP: outgoing message end.
HTTP: outgoing message end.
HTTP: outgoing message end.
HTTP: outgoing message end.
HTTP: outgoing message end.

[chrisdickinson]

You are using the default (pooled) http agent from the client, which limits the number of maximum open connections to the same server to 5. In addition, the r variable received in the callback is a ClientResponse, which is a paused readable stream. In order to free the socket back to the agent pool, you must exhaust the ClientResponse:

var http = require('http');
http.createServer(function (req, res) {
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end('Hello World\n');
}).listen(2000);

var ix = 0;
setInterval(function () {
    http.get('http://localhost:2000/', function (res) {
      // enter flowing mode
      res.resume();
      console.log({ix: ix++, status: res.statusCode});
    });
}, 200);

While this isn't a bug, it would be great to add to the http.get and http.request documentation so that future users aren't surprised by this behavior! Would you care to do the honors?