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Amazon CloudWatch monitors your Amazon Web Services (AWS) resources and the applications you run on AWS in real-time. You can use CloudWatch to collect and track metrics, which are the variables you want to measure for your resources and applications. CloudWatch alarms send notifications or automatically make changes to the resources you are monitoring based on rules that you define. For example, you can monitor the CPU usage and disk reads and writes of your Amazon Elastic Compute Cloud (Amazon EC2) instances and then use this data to determine whether you should launch additional instances to handle increased load. You can also use this data to stop under-used instances to save money. In addition to monitoring the built-in metrics that come with AWS, you can monitor your own custom metrics. With CloudWatch, you gain system-wide visibility into resource utilization, application performance, and operational health.
The rest of this section introduces the key concepts and terms that will help you understand what you need to do to monitor your resources and applications with CloudWatch.
The Getting Set Up with CloudWatch section walks you through the process of signing up for AWS and setting up the CloudWatch command-line interface (CLI). The Getting Started with CloudWatch section walks you through the process of publishing metrics, getting statistics, and setting alarms.
Amazon CloudWatch is basically a metrics repository. An AWS product—such as Amazon EC2—puts metrics into the repository, and you retrieve statistics based on those metrics. If you put your own custom metrics into the repository, you can retrieve those statistics as well.
You can use metrics to calculate statistics and present the data graphically in the CloudWatch console. For more information about the other AWS resources that generate and send metrics to CloudWatch, see Amazon CloudWatch Namespaces, Dimensions, and Metrics Reference.
You can configure alarm actions to stop, start, or terminate an Amazon EC2 instance when certain criteria are met. In addition, you can create alarms that initiate Auto Scaling and Amazon Simple Notification Service (Amazon SNS) actions on your behalf. For more information about creating CloudWatch alarms, see Alarms.