Amazon.com has added some new control features to its flagship EC2 cloud-computing service. The new features are load balancing, auto scaling, and cloud monitoring -- giving developers extra tools to track, monitor and adjust their use of EC2. It's the latest in a series of tweaks and add-ons to Amazon's suite of cloud services.

Here's how Amazon web services evangelist Jeff Barr describes the new controls in a blog post:

Amazon CloudWatch tracks and stores a number of per-instance performance metrics including CPU load, Disk I/O rates, and Network I/O rates. The metrics are rolled-up at one minute intervals and are retained for two weeks. Once stored, you can retrieve metrics across a number of dimensions including Availability Zone, Instance Type, AMI ID, or Auto Scaling Group. Because the metrics are measured inside Amazon EC2 you do not have to install or maintain monitoring agents on every instance that you want to monitor. You get real-time visibility into the performance of each of your Amazon EC2 instances and can quickly detect underperforming or underutilized instances.

Auto Scaling lets you define scaling policies driven by metrics collected by Amazon CloudWatch. Your Amazon EC2 instances will scale automatically based on actual system load and performance but you won't be spending money to keep idle instances running. The service maintains a detailed audit trail of all scaling operations. Auto Scaling uses a concept called an Auto Scaling Group to define what to scale, how to scale, and when to scale. Each group tracks the status of an application running across one or more EC2 instances. A set of rules or Scaling Triggers associated with each group define the system conditions under which additional EC2 instances will be launched or unneeded EC2 instances terminated. Each group includes an EC2 launch configuration to allow for specification of an AMI ID, instance type, and so forth.

Finally, the Elastic Load Balancing feature makes it easy for you to distribute web traffic across Amazon EC2 instances residing in one or more Availability Zones. You can create a new Elastic Load Balancer in minutes. Each one contains a list of EC2 instance IDs, a public-facing URL, and a port number. You will need to use a CNAME record in your site's DNS entry to associate your this URL with your application. You can use Health Checks to ascertain the health of each instance via pings and URL fetches, and stop sending traffic to unhealthy instances until they recover.