parallel requests to SimpleDB in node

web.js

var express = require('express'),
    simpledb = require('simpledb'),
    Step = require('step'),
    
    sdb = new simpledb.SimpleDB({
        keyid: 'your aws key',
        secret: 'your aws secret'
    }),
    
    app = express.createServer(express.logger()),
    
    REQUESTS = 50;

// Query SimpleDB
function sdb_request(callback) {
    sdb.select("select field from INTERACTIONS",
    function(error, result, meta) {
        callback(error, result);
    });
}

// 50 calls guaranteed to return in order, when one completes another is made
app.get('/sync',
    function(request, response) {
        var start = new Date().getTime();
        function looper(incr) {
            // We loop using this recursive function.
            if (incr == REQUESTS) {
                // Stopping condition
                var end = new Date().getTime();
                var time = end - start;
                // Exit here
                response.send(REQUESTS + " synchronous calls to SimpleDB took: " + time);
            } else {
                sdb_request(function(err, result) {
                    if (err) {
                        throw err;
                    } else {
                        looper(incr + 1);
                        // call again!
                    }
                });
            }
        }
        looper(0); // start loop @ 0
    }
);


// 50 parallel calls, may not return in order, final function called when done with each response
app.get('/parallel',
    function(request, response) {
        var start = new Date().getTime();
        Step(
            function() {
                for (var i = 0; i < REQUESTS; i++) {
                    sdb_request(this.parallel()); // special callback provided by Step
                }
            },

            function(err, result1, result2, result3) { // etc, there will be 51 params
                // each result is available as an argument to the final function, see this.arguments
                if (err) {
                    throw err;
                }
                var end = new Date().getTime();
                var time = end - start;
                // Exit here
                response.send(REQUESTS + " parallel calls to SimpleDB took: " + time);
            }
        );
    }
);

var port = process.env.PORT || 3000;
app.listen(port,
function() {
    console.log("Listening on " + port);
});