Create a cache expiration rule

Scenarios

CDN nodes respond to requests based on the cache status. If the requested resource is not cached on CDN nodes, the request is redirected to the origin server to retrieve the resource. After the resource is retrieved from the origin server, an HTTP 2XX status code is returned to the CDN node. The retrieved resource is cached on the CDN node and also returned to the client.

If resources on your origin server are updated but the resources cached on CDN nodes are not, CDN nodes may return outdated resourced to clients or respond to requests slowly. In this case, you can create a cache expiration rule. After resources expire based on the cache expiration rule, CDN nodes retrieve the latest resources from the origin server. We recommend that you set a greater TTL value for infrequently requested resources. This increases the cache hit ratio and accelerates content delivery.

Procedure

When you update resources on the origin server, we recommend that you use different names for different versions of the same resource. This separates outdated and updated resources on the origin server. You can use version numbers to indicate different versions of a resource, for example, img-v1.0.jpg and img-v2.1.jpg.

1. Log on to the Alibaba Cloud CDN console.
2. In the left-side navigation pane, click Domain Names.
3. On the Domain Names page, find the domain name that you want to manage and click Manage in the Actions column of the domain name.
4. In the management pane of the domain name, click Cache.
5. On the Cache Expiration tab, click Create Rule.
6. In the Create Expiration Rule dialog box, set the parameters.
   

   Parameter	Description
   Type	You can select Directory or File Extension. Select a type based on your business requirements. Directory: specifies the resources that are cached in the specified directory. File Extension: specifies the file types of the cached resources.
   Object	If you select Directory, take note of the following rules: You can add only one directory in each rule. You can enter a full path. It must start with a forward slash (/), for example, /directory/aaa. If you select File Extension, take note of the following rules: You can enter one or more file extensions. Separate multiple file extensions with commas (,), for example, JPG,TXT. You cannot use an asterisk (*) to specify all file types.
   Expire In	Specify the TTL value of the cached resources. You can set the TTL value to at most three years. Specify a TTL value of one month or longer for static files that are infrequently updated, such as images and application packages. Specify a TTL value based on your actual workloads for static files that are frequently updated, such as JS and CSS files. Specify a TTL value of 0 seconds to disable caching for dynamic files, such as PHP, JSP, and ASP files.
   Weight	Specify the weight of the cache expiration rule. The weight indicates the priority of the cache expiration rule. Valid values are from 1 to 99. A greater value indicates a higher priority. Note We recommend that you specify a different weight for each cache expiration rule. If rules have the same weight, they are randomly applied. If you have created multiple cache expiration rules for a cached resource, only the first matched rule is applied.

7. Click OK.

   After a cache expiration rule is created, it is displayed on the Cache Expiration tab. You can Modify or Delete the rule.

Examples

Related API operations

BatchSetCdnDomainConfig