Monitoring application and service availability

CloudWatch helps you monitor and analyze the performance and runtime aspects of your applications and workloads. You should also monitor the availability and reachability aspects of your applications and workloads. You can achieve this by using an active monitoring approach with Amazon Route 53 health checks and CloudWatch Synthetics.

You can use Route 53 health checks when you want to monitor connectivity to a webpage through HTTP or HTTPS, or network connectivity through TCP to a public Domain Name System (DNS) name or IP address. Route 53 health checks initiate connections from the Regions that you specify on ten-second or 30-second intervals. You can choose multiple Regions for the health check to run in, each health check runs independently, and you must choose at least three Regions. You can search the response body of an HTTP or HTTPS request for a specific substring if it appears in the first 5,120 bytes of data returned for health check evaluation. An HTTP or HTTPS request is considered healthy if it returns a 2xx or 3xx response. Route 53 health checks can be used to create a composite health check by checking the health of other health checks. You can do this if you have multiple service endpoints and you want to perform the same notification when one of them becomes unhealthy. If you use Route 53 for DNS, you can configure Route 53 to fail over to another DNS entry if a health check becomes unhealthy. For each critical workload, you should consider setting up Route 53 health checks for external endpoints that are critical for normal operations. Route 53 health checks can help you avoid writing failover logic into your applications.

CloudWatch synthetics allows you to define a canary as a script to evaluate the health and availability of your workloads. Canaries are scripts written in Node.js or Python and work over HTTP or HTTPS protocols. They create Lambda functions in your account that use Node.js or Python as a framework. Each canary that you define can perform multiple HTTP or HTTPS calls to different endpoints. This means you can monitor the health of a series of steps, such as a use case or an endpoint with downstream dependencies. Canaries create CloudWatch metrics that include each step that was run so you can alarm and measure different steps independently. Although canaries require more planning and effort to develop than Route 53 health checks, they provide you with a highly customizable monitoring and evaluation approach. Canaries also support private resources running within your virtual private cloud (VPC), which makes them ideal for availability monitoring when you don’t have a public IP address for the endpoint. You can also use canaries to monitor on-premises workloads as long as you have connectivity from within the VPC to the endpoint. This is particularly important when you have a workload that includes endpoints that exist on premises.