Feature Overview

When CDN POPs obtain resources from an origin server, the origin server returns negative http status codes. In the eSurfing Cloud CDN console, you can configure a cache TTL for negative status codes such as 4XX and 5XX. If a client requests the same resource again before cache TTL expires, CDN directly returns the cached status code instead of sending the request to the origin server. This reduces the workload on the origin server. One the cache expires, a request for the same resource is sent to the origin server.

Typical scenario: A client continues to request file X after the file is deleted from an origin server. In this scenario, all the requests are redirected to the origin server because CDN POPs do not cache the file. As a response, the origin server returns a 4XX status code. This significantly increases the workload of the origin server. If you specify that CDN POPs cache a 4XX status code, the 4XX status code is cached on the POPs after the first back-to-origin request for file A. If a client requests the file again before the preset expiration time, the CDN POPs directly return a 4XX status code instead of sending the request to the origin server.

Note: If no expiration time is configured for status codes, CDN caches 4XX status codes based on the cache settings of the origin server and does not cache 5XX status codes by default. If the expiration time is configured, CDN ignores cache headers from the origin server and caches status codes based on the time configured in the CDN console. The cache headers include Pragma: no-cache, Cache-Control, and Expires. The priorities of these headers are sorted in descending order as follows: Pragma: no-cache/Cache-Control: no-cache/private/no-store > Cache-Control: max-age=n(n>=0) > Expires.

Procedure

Log in to the CDN console.
Go to Domain Management -> Domain List page.
On the Domain List page, find the target domain name, and click Edit in the Actions column.
Click Cache .
Click the Status Code Expiration tab.
Click Add and setup cache TTL for status codes.
Click OK and Save.

Notes:

Select a unit for Expire In , such as seconds, minutes, hours, or days. Then, enter the TTL.
Enter one or more error status codes that you need to cache into the Status Code field. Separate the status codes with commas (,). Enter valid status codes such as 404 and 500.
For 3xx status code, 301/302 is supported, while 304 is not supported.

Content Delivery Network

Cache TTL for HTTP status code