Health checking

Certain routing policies in Route 53 also support health checks. A health check will allow the DNS service to check the target and determine whether the response it receives is healthy or not. A Route 53 health check can either be TCP or HTTP/HTTPS based. The TCP check will simply check the response on the port, while a HTTP/HTTPS health check can also check for a specific string in the origin. Health checks can also include a maximum response time, which can also determine whether the site is responding too slowly to be of any use to clients.

The health-check operation is demonstrated in the following diagram:

Considering the preceding diagram, we see the following:

1. The user requests the address, packtpub.com
2. The Route 53 service checks the origins and determines a healthy host
3. The address of the healthy host is returned to the user

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