When a point of presence (POP) retrieves a resource from the origin server, the origin server returns an HTTP status code. You can configure a cache time-to-live (TTL) for the HTTP status code in the Edge Security Acceleration (ESA) console. When a client requests the same resource, the POP returns the HTTP status code without triggering origin fetch. This reduces loads on the origin server. After a cached HTTP status code expires, requests that trigger the code are redirected to the origin server.
Scenarios
The cache TTL of HTTP status codes is used to specify the period during which caching operations can be performed on the POP when the origin server returns an abnormal HTTP status code.
In normal cases where a POP retrieves the requested resource from the origin server and the origin server returns an HTTP 2xx status code, the resource is cached based on default cache rules. If the origin server cannot quickly return all HTTP status codes, such as non-HTTP 2xx status codes, and you do not want all requests to be responded by the origin server, you can configure a cache TTL for HTTP status codes to allow POPs to return HTTP status codes. This reduces loads on the origin server.
Sample scenario
File A is deleted from the origin server and is not cached on POPs. When clients continue to request the file, all requests for file A are redirected to the origin server. The origin server returns an HTTP 4xx status code for all the requests. This increases loads on the origin server. If you configure a cache TTL for the HTTP 4xx status code, POPs cache the HTTP 4xx status code after the first request for file A is responded by the origin server. During the TTL, when a client requests file A again, the POP returns the HTTP 4xx status code without redirecting the request to the origin server.
Procedure
Log on to the ESA console.
In the left-side navigation pane, click Websites.
On the Websites page, find the website that you want to manage, and click the website name or View Details in the Actions column.
In the left-side navigation tree, choose .
Click Create Rule and specify the Rule Name parameter.
In the If requests match... section, specify the conditions for matching incoming requests. For more information about how to configure a rule, see Overview.
In the Bypass Cache section, specify whether to bypass cache. For more information, see Bypass cache.
In the Edge Cache TTL section, click Configure.
Click Add next to Status Code Cache TTL, select an HTTP status code, and specify the TTL.
Click OK.