Scaling up using child processes

parent-and-child-processes.js

// ////////////////
// Parent
// ////////////////
...
var cp = require('child_process');
...
//TODO use config to decide how many child processes to start
var NUM_KIDS = 2;
var PRODUCT_IDS = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 
                   '10', '11', '12', '13', '14', '15', '16', '17', '18', '19',
                   ...
                  ];
 
var chunk = PRODUCT_IDS.length / NUM_KIDS;
var kids = new Map();
for (var i=0, j=PRODUCT_IDS.length; i<j; i+=chunk) {
    var n = cp.fork('./lib/trading-engine-child.js');
    n.on('message', messageFromChild);
    var temparray = PRODUCT_IDS.slice(i,i+chunk);
    logger.info('created child process for products ' + temparray);
    _.each(temparray, function(e){
        logger.debug('mapping productId "' + e + '" to child process ' + n.pid);
        kids.set(e, n);
    });
}
...

// ////////////////
// Child
// ////////////////
process.on('message', function(model) {
    logger.debug('received command: "' + model.command + '"');
    if(model.command == t.EventType.PURCHASE){
        var buyer = ...
        var po = new m.PurchaseOrder(model.what.productId, model.what.quantity, model.what.maxPrice, model.id);
        buyer.addPurchaseOrder(po);
    }else if(model.command == t.EventType.SALE){
        ...
    }else{
        var msg = 'Unknown command ' + model.command;
        process.send({id: model.id, err: msg});            
    }
});