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Amazon CloudWatch Events
User Guide

What is Amazon CloudWatch Events?

Amazon CloudWatch Events delivers a near real-time stream of system events that describe changes in Amazon Web Services (AWS) resources to AWS Lambda functions, Amazon SNS topics, Amazon SQS queues, streams in Amazon Kinesis Streams, or built-in targets. Using simple rules that you can quickly set up, you can match events and route them to one or more target functions or streams. CloudWatch Events becomes aware of operational changes as they occur. CloudWatch Events responds to these operational changes and takes corrective action as necessary, by sending messages to respond to the environment, activating functions, making changes, and capturing state information.

Concepts

Before you begin using CloudWatch Events, you should understand the following concepts:

  • Events—An event indicates a change in your AWS environment. AWS resources can generate events when their state changes. For example, Amazon EC2 generates an event when the state of an EC2 instance changes from pending to running, and Auto Scaling generates events when it launches or terminates instances. AWS CloudTrail publishes events when you make API calls. You can generate custom application-level events and publish them to CloudWatch Events. You can also set up scheduled events that are generated on a periodic basis.

  • Targets—A targets processes events. Targets include AWS Lambda functions, Amazon SNS topics, Amazon SQS queues, Amazon Kinesis streams, or built-in targets (such as CloudWatch alarm actions). A target receives events in JSON format.

  • Rules—A rule matches incoming events and routes them to targets for processing. A single rule can route to multiple targets, all of which are processed in parallel. Rules are not processed in a particular order. This enables different parts of an organization to look for and process the events that are of interest to them. A rule can customize the JSON sent to the target, by passing only certain parts or by overwriting it with a constant.

The following services are used in conjunction with CloudWatch Events:

  • AWS CloudTrail enables you to monitor the calls made to the CloudWatch Events API for your account, including calls made by the AWS Management Console, the AWS CLI and other services. When CloudTrail logging is turned on, CloudWatch Events writes log files to an S3 bucket. Each log file contains one or more records, depending on how many actions are performed to satisfy a request. For more information, see Logging Amazon CloudWatch Events API Calls in AWS CloudTrail.

  • AWS Identity and Access Management (IAM) helps you securely control access to AWS resources for your users. Use IAM to control who can use your AWS resources (authentication), what resources they can use, and how they can use them (authorization). For more information, see Authentication and Access Control for Amazon CloudWatch Events.

  • Amazon Kinesis Streams enables rapid and continuous data intake and aggregation. The type of data used includes IT infrastructure log data, application logs, social media, market data feeds, and web clickstream data. Because the response time for the data intake and processing is in real time, processing is typically lightweight. For more information, see the Amazon Kinesis Streams Developer Guide.

  • AWS Lambda enables you to build applications that respond quickly to new information. Upload your application code as Lambda functions and Lambda runs your code on high-availability compute infrastructure. Lambda performs all the administration of the compute resources, including server and operating system maintenance, capacity provisioning, automatic scaling, code and security patch deployment, and code monitoring and logging. For more information, see the AWS Lambda Developer Guide.