Edge Security Acceleration:Configure Range origin fetch

How it works

Range is an HTTP request header that specifies the range of content to retrieve. For example, Range: bytes=0-100 requests the first 101 bytes of a file.

After you enable Range origin fetch, when DCDN receives a user request and the resource is not cached on the DCDN node or has expired, the node uses Range requests to retrieve the required portion of the resource from the origin server in segments and caches it locally.

Prerequisites

• The origin server supports Range requests. The HTTP request header must contain the Range field, and the origin server must respond with HTTP 206 Partial Content. If the origin server does not support Range requests, enabling Range origin fetch prevents resources from being cached.

Considerations

Before you configure Range origin fetch, note the following:

• Multipart Ranges — The Multipart Ranges feature is disabled by default. Enabling Range origin fetch does not automatically enable Multipart Ranges. Submit a ticket to request access to the Multipart Ranges feature.

• QPS impact — Enabling Range origin fetch increases the QPS to the origin server. If the origin server has rate limiting configured, take precautions to avoid triggering rate limits. You can use DescribeL2VipsByDomain to query the IP addresses of DCDN origin fetch nodes and add them to the origin server's IP allowlist.

• Rule engine priority — When Range origin fetch references rule conditions in the rule engine, the execution order follows the priority of rule conditions configured in the rule engine, not the priority configured for this feature.

Procedure

DCDN

1. On the Origin Fetch tab, find Range Origin Fetch and click Modify.

2. Set Range origin fetch to Disable, Follow Client Range Request, or Enable (Recommended If Large Files Requested) based on the following parameter descriptions.

   When you set Range origin fetch to Enable (Recommended If Large Files Requested) or Follow Client Range Request, you can also configure Chunk Size. The default chunk size is 512 KB.

   Parameter	Option	Description
   Range Origin Fetch	Disable	Range origin fetch is disabled by default. Regardless of whether the client uses Range requests to the node, the node requests the entire file from the origin server. This results in lower file distribution efficiency in large file scenarios.
   	Follow Client Range Request	The node sends Range requests to the origin server only when the client includes Range in its requests. The first origin fetch request rounds up to the nearest multiple of the chunk size based on the Range size in the client request. All subsequent requests use the specified chunk size.
   	Enable (Recommended If Large Files Requested)	The node always sends Range requests to the origin server, regardless of whether the client includes Range in its requests. All origin fetch Range requests use the specified chunk size. This option is recommended for large file scenarios.
   Chunk Size	512 KB, 1 MB, 2 MB, 4 MB	When Range origin fetch is set to Follow Client Range Request or Enable (Recommended If Large Files Requested), you can configure the chunk size. The default chunk size is 512 KB.
   Rule Conditions	Disable	Rule conditions identify parameter information carried in user requests to determine whether the Range origin fetch configuration applies to a specific request.