A simple demonstrantion of a sheduler done in Node.JS. Tasks can be split up in multiple Queues. Tasks can be marked as "exclusive" if they should not be run concurrent with other tasks.

scheduler.js

var http = require('http'),
    async = require('async'),
    queueBuilder,
    taskBuilder,
    counter,
    maxConcurrent = Number.POSITIVE_INFINITY,
    debug = true,
    queues = {},
    tasks = {};

// Some Helper functions, used for debugging / logging:

counter = (function() {
  var current = 0;
  return function() {
    return ++current;
  } 
})();

debugTaskBuilder = function(task, debugBefore, debugAfter) {
  return function(cb) {
    console.log(debugBefore);
    task.call(this, function() {
      console.log(debugAfter);
      cb();
    });
  };
};

// Tasks which get executed by workers
// within the Queue

tasks.fakeTimeout = function(cb) {
  setTimeout(function() {
    cb();
  }, Math.floor((Math.random()*10000)+1));
};

tasks.httpRequest = function(cb) {
  http.get("http://www.spiegel.de", function(res) {
    cb();
  });
};

tasks.concurrencyOne = function(cb) {
  this.concurrency = 1;
  cb();
};

tasks.concurrencyMax = function(cb) {
  this.concurrency = maxConcurrent;
  cb();
};

// Queue factory

queueBuilder = function() {
  var queue = async.queue(function(task, cb) {
    task.call(queue, function() {
      cb();
    });
  }, maxConcurrent);
  return queue;
};

// Build Queues

queues.cook = queueBuilder();
queues.wash = queueBuilder();

// Adding Tasks:
// Normal: http://127.0.0.1:9999/?queue=wash
// Exclusive: http://127.0.0.1:9999/?queue=wash&exclusive=1
// Specific Task: http://127.0.0.1:9999/?queue=wash&task=httpRequest

http.createServer(function(req, res) {
  var query = require('url').parse(req.url,true).query;
  
  if (!(query.queue && queues[query.queue])) {
    res.end('0');
    return;
  }

  var id = counter(),
      queue = queues[query.queue],
      task = (query.task && tasks[query.task])?query.task:'fakeTimeout';

  if (query.exclusive == 1) {

    // Set Concurreny to 1 before running
    // an exclusive task
    queue.push(tasks.concurrencyOne);

    // Add Exclusive Task
    if (debug) {
      queue.push(debugTaskBuilder(tasks[task], 
        'Start exclusive Task #'+id+' in Queue ' + query.queue,
        'End exclusive Task #'+id
      ));
    } else {
      queue.push(tasks[task]);
    }

    // Set Concurrency back to maxConcurrent
    queue.push(tasks.concurrencyMax);
  } else {

    // Add Normal Task
    if (debug) {
      queue.push(debugTaskBuilder(tasks[task], 
      'Start Task #'+id+' in Queue ' + query.queue,
      'End Task #'+id
    ));
    } else {
      queue.push(tasks[task]);
    }
  }
  res.end('1');
}).listen(9999);

AB Ergebnis. 1 Millionen Requests / 100 Parallel:

simon@simon-desktop:~/Arbeitsfläche/sheduler$ ab -n 1000000 -c 100 http://127.0.0.1:9999/?queue=wash
This is ApacheBench, Version 2.3 <$Revision: 655654 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 127.0.0.1 (be patient)
Completed 100000 requests
Completed 200000 requests
Completed 300000 requests
Completed 400000 requests
Completed 500000 requests
Completed 600000 requests
Completed 700000 requests
Completed 800000 requests
Completed 900000 requests
Completed 1000000 requests
Finished 1000000 requests


Server Software:        
Server Hostname:        127.0.0.1
Server Port:            9999

Document Path:          /?queue=wash
Document Length:        1 bytes

Concurrency Level:      100
Time taken for tests:   160.431 seconds
Complete requests:      1000000
Failed requests:        0
Write errors:           0
Total transferred:      76000000 bytes
HTML transferred:       1000000 bytes
Requests per second:    6233.19 [#/sec] (mean)
Time per request:       16.043 [ms] (mean)
Time per request:       0.160 [ms] (mean, across all concurrent requests)
Transfer rate:          462.62 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.0      0       4
Processing:     1   16   8.3     16      54
Waiting:        1   16   8.3     15      54
Total:          2   16   8.3     16      54

Percentage of the requests served within a certain time (ms)
  50%     16
  66%     20
  75%     22
  80%     23
  90%     27
  95%     31
  98%     34
  99%     37
 100%     54 (longest request)
simon@simon-desktop:~/Arbeitsfläche/sheduler$