Feature Overview

eSurfing Cloud Content Delivery Network (CDN) supports the following methods of purging: URL-based purge, directory-based purge, and regex-based purge. These methods have different implementation mechanisms while they ensure that users can access the latest content. The purge feature is often used to remove stale contents on CDN nodes after the contents on origin servers are updated.

• URL-based Purge : After a URL-based purge task is executed, the cache entries corresponding to the specified URLs are deleted from CDN POPs directly. When a client sends a request for accessing the content corresponding to the URL to a CDN POP, the CDN POP will send a request to origin to get the new content. After the CDN POP receives the new content from the origin server, the content will be stored in cache and passed to the client at the same time.

• Directory-based Purge and regex-based Purge : After a directory-based or regular expression-based purge task is executed, the corresponding cached entries are marked as stale despite of the cache TTL. When a client sends a request for accessing the content to a CDN POP, the CDN POP will send a request with the If-Modified-Since or If-None-Match header to the origin server to check whether the content is updated on origin. If the origin server returns the 304 status code that indicates the content on the origin server is not updated, the CDN POP only updates the cache status and does not pull the content from the origin server. In such a case, the CDN POP returns the cached content to the client. If the origin server returns the 200 or 206 status code that indicates the content on the origin server is updated. The CDN POP will receive the new content from the origin server and store it in cache, and then pass the new content to the client.

Procedure

Log in to the CDN console.
Go to Purge & Prefetching page,
Click Create Task .
Select URL Purge , Directory Purge , or Regex Purge based on your business requirements.
Follow the instructions to enter the required information. If you select URL Purge , enter the URLs that you want to update.
After you complete the configuration, click Submit .

Options	Descriptions
URL Purge	Specify the explicit URLs for purge, starting with http:// OR https://, for example, http://www.example.com/images/test.jpg, one URL per line (carriage return–linefeed)，the characters in the URL are case-sensitive.
Directory Purge	Specify the diectory for purge, starting with http:// OR https:// and ending with a slash(/), for example, http://www.example.com/images/ If not other special configurations, diectroy purge should start with HTTP. one URL per line (carriage return–linefeed)，the characters in the URL are case-sensitive.
Regex Purge	Specify the Regex for purge, starting with http:// OR https://, for example, http://www.example.com/\w+， one URL per line (carriage return–linefeed)，the characters in the URL are case-sensitive.

Additional Considerations

Update CDN caches irregularly. When your origin server content is updated and users need to access the latest resources, you can achieve this by submitting a purge task.
Bulk purge and prefetching taks may cause high-concurrency origin requests. If the origin server's egress bandwidth is small, it is recommended to submit tasks in small scale.
Each URL should be on a separate line (use line breaks). Each submission can contain up to 50 lines, and pay attention to the case sensitivity of letters in the URLs. Purge tasks generally take effect within 5 to 10 minutes.
By default, http and https share the same caches, and the directory purge should be submitted using the HTTP protocol(starting with http://). If the target domain has special configurations to cache http and https respectively, please specify the actual contents need to be purged as you need.
Purge quotas:

URL purge: 10,000 entries/day/account.
Directory purge: 100 entriesday/account.
Regex refresh: 10 entries/day/account (maximum limit of 10 entries/day for a single domain).

Notes:

To prevent resource abuse, the eSurfing Cloud CDN platform has limited the allocated usage of various service resources. If the current usage cannot meet your needs, please contact our customer support team via hotline (852)31000000 or email global.noc@chinatelecomglobal.com to request an increase in quotas. Quota adjustments will be evaluated and configured based on the actual needs of your business.