Run 10000 async calls through a sequencer in blocks of 500

example-sequence-10k-in-blocks-of-500.js

//
// Example #2 : sequence 10000 async calls in blocks of 500 using a collector
// 

function sequence(arr) {
  var self = function() {
    arr.length && arr.shift()(self);
  }
  self();
}

function collect(arr, finalCallback) {
  var size = arr.length;

  for (var i=0; i<arr.length; i++) {
    arr[i](function() {
        if (--size == 0) {
          console.log("Finished block");
          finalCallback();
        }
      }
    );
  }
}

//
// Build an array with 10000 sequencable async calls
//

var asyncCalls = [];

for (var i=0;i<10000;i++) {
  (function(no) {
      asyncCalls.push(
        function(callback) {
          console.log("Call #" + no);
          setTimeout(callback, 0); // Simulate async
        }
      );
    })(i);
}

//
// Chop the 10000 calls into blocks of 500
//

var BLOCKSIZE = 500;
var blocks = [];

do {
  blocks.push(asyncCalls.splice(0,BLOCKSIZE));
} while(asyncCalls.length != 0);

//
// Build a new sequence for collecting each block
//

var sequenceCalls = [];

for (var i=0; i<blocks.length; i++) {
  (function(offset) {
      sequenceCalls.push(
        function(callback){
          collect(blocks[offset], function() {
              console.log("Finished block #" + offset);
              callback();
            });
        })
    })(i);
}

//
// Add a finishing function at the end
//

sequenceCalls.push(function(callback) {
    console.log("Finished all tasks");
  });

sequence(sequenceCalls);