gistfile1.js

/* Simplified implementation of ranger stat server using node.js. */
var sys = require('sys'),
    http = require('http');
var buffer = '';
var ring = new Array();
var window = 300; // how wide is the window?
var percentile = 0.95;
var server;

// stdin worker
process.stdio.open();
process.stdio.addListener('data', function(chars){
        buffer = buffer + chars;
        while (true) {
            var nl = buffer.indexOf('\n');
            if (nl >= 0) {
                var line = buffer.substring(0, nl);
                buffer = buffer.substring(nl + 1);
                try { 
                    var entry = JSON.parse(line);
                } catch(err) {
                    sys.puts('JSON parse error: ' + err);
                    continue;
                }
                if (entry.servlet == 'home') {
                    if (entry.status_code != 200)
                        continue;
                    var elapsed = entry.response_write_time - entry.log_begin_time;
                    if (!elapsed)
                        continue;
                    ring.push({'start': entry.log_begin_time, 'elapsed': elapsed});
                    var i = 0;
                    while (entry.log_begin_time - ring[i].start > window)
                        i++;
                    if (i)
                        ring = ring.slice(i) // memcpy :-(
                }
            } else
                break;
        }
});
process.stdio.addListener('close', function() {
        sys.puts('No more data to process, shutting down HTTP server');
        if (server)
            server.close();
});

// http server
server = http.createServer(function(req, resp) {
        var body;
        if (ring.length < 20)
            body = "too few requests, only have " + ring.length + ' items in buffer\n';
        else {
            var times = new Array();
            for (i = 0; i < ring.length; i++)
                times.push(ring[i].elapsed);
            times.sort();
            body = (times[(times.length * percentile) | 0] * 1000).toFixed(2) + ' ms with ' + ring.length + ' items in buffer\n'; 
        }
        resp.sendHeader(200, {
                "Content-Length": body.length,
                "Content-Type": "text/plain"
        });
        resp.sendBody(body);
        resp.finish();
});
server.listen(8080, "localhost");