qhttp-agent

Note: this package is deprecated, use the http.Agent included in newer nodejs.

Edited version of http.Agent from node-v0.10.29

This is a drop-in replacement for http.Agent that fixes connection reuse and speeds up requests by up to 50%. All connections are opened with keepAlive: true. This version is not an event emitter, and does not emit Agent events.

Fixes the socket TIME_WAIT leak, fixes connection reuse, and is overall much faster than the one in in node-v0.10. Uses a timeout thread to harvest idle sockets if socket.unref is not available, so might work with node-v0.8 too.

    npm install qhttp-agent
    npm test qhtt-pagent

Usage

new HttpAgent( [options] )

HttpAgent is passed in as an option to http.request to be used in place of http.globalAgent.

    HttpAgent = require('qhttp-agent');
    var agent = new HttpAgent(options);

Options

• maxSockets - limit connections to each destination (default 5)
• socketIdleTimeout - how long to hold on to an open socket before releasing it (default 2000 ms)
• allowHalfOpen - allow sockets to be closed for writes but still be read (default false)

http.Agent passes all options to net.createConnection. This seems odd, but HttpAgent emulates this behavior, so socket options can be included as well (eg allowHalfOpen).

Example

    var http = require('http');
    var HttpAgent = require('qhttp-agent');
    var requestOptions = {
        method: "GET",
        host: "google.com",
        path: "/",
        agent: new HttpAgent(),
    };
    var req = http.request(requestOptions, function(res) {
        var body = "";
        res.on('data', function(chunk) {
            body += chunk;
        });
        res.on('end', function() {
            console.log(res.headers);
            console.log(body);
            res.socket.end();
        });
    });
    req.write("");
    req.end();

Analysis

The node-v0.10.29 http.Agent only reuses a keepAlive connection if a second request arrives before the first finishes. Then the second request will be sent on the same connection as the first, otherwise the connection is closed. It would be better to keep around the open socket and reuse it.

Also, the http.Agent maxSockets option limits the number of connection per host:port destination, not the overall number of sockets allowed. The default of 5 still allows an unlimited number of concurrent connections. This is counter-intuitive.

As a consequence of the above, allowing more sockets makes it less likely that any socket will be reused. Even the default 5 is too many in some cases. All the closed sockets enter a TIME_WAIT state and become unusable for 60 seconds, making a scarce resource even scarcer.

Related Work

agentkeepalive - another keepAlive agent, a little slower