Modifications to the node.jsj trading engine

trading-engine-persistSales.js

function persistSales(sales, callback){
    if(sales.length === 0 || process.env.skipPersistence) {
        callback(); //nothing to do, so continue immediately
    }else{
        resources.dbConnection(function(err, connection) {
            if(err) callback(err); else {
                logger.info('preparing to persist ' + sales.length + ' sales');
                var count = sales.length;
                _.each(sales, function(sale){ //save them in parallel
                    connection.query(
                            'INSERT INTO SALES (BUYER_NAME, SELLER_NAME, PRODUCT_ID, PRICE, QUANTITY, PO_ID, SO_ID) values (?, ?, ?, ?, ?, ?, ?)',
                            [sale.buyer.name, sale.seller.name, sale.productId, sale.price, sale.quantity, sale.po.id, sale.so.id],
                            function(err, rows, fields) {
                                if(err) callback(err); else {
                                    sale.id = rows.insertId;
                                    count--;
                                    if(count == 0){
                                        logger.info('persisted all sales');
                                        connection.release();
                                        callback();
                                    }
                                }
                            }
                    );
                });
            }
        });
    }
}