Custom Cache Key - Edge Security Acceleration - Alibaba Cloud Documentation Center

You can configure custom cache keys by creating rules that generate cache keys based on different parts of an HTTP request, such as the URI, request parameters, HTTP request headers, or custom variables. This feature converts requests for the same file into a single cache key, which prevents the same request from being cached as different files. As a result, this improves the cache hit rate, reduces origin fetches, and decreases response times and bandwidth consumption.

Use cases

Important

The custom cache key feature modifies only the cache identifier of a request and does not change the origin fetch URL. The content of the origin fetch request remains the same as the client request.

A cache key is a unique identifier for a file cached on a DCDN point of presence. By default, the cache key is the client’s request URL, including query parameters.

Use case 1

Clients send requests with complex query parameters. Even when multiple requests access the same file, different parameter values cause DCDN points of presence to treat them as requests for different files. Consequently, DCDN caches multiple copies and increases the number of origin fetches.

Use custom cache key rules to unify cache keys for similar requests. This reduces origin fetches.

Use case 2

Clients send identical URLs. DCDN treats these as requests for the same file. However, HTTP headers include a client field that distinguishes client systems. You want DCDN to treat these requests as distinct files. 场景一

Add the value of the client header to the cache key. DCDN then treats the two requests as having different cache keys. 场景二

Procedure

Log on to the DCDN console.
In the left-side navigation pane, click Domain Names.
On the Domain Names page, find the domain name that you want to manage and click Configure.
In the left-side navigation tree of the domain name, click Caching.

On the Custom Cache Key tab, configure the custom cache key.

Note

You can modify the URI, query parameters, and HTTP headers. You can also define custom variables to extract fields from requests. The final cache key combines four parts: URI, parameter operations, HTTP headers, and custom variables.

自定义Cachekey

Parameter Type	Operation Description
Rule Condition	Rule conditions identify various parameters in a user request to determine whether a configuration applies to the request. Do not use: Do not use rule conditions. To add or edit rule conditions, manage them in the Rules Engine.
URIs	If the client’s request URI matches the configured Source URI, DCDN replaces the origin URI with the configured Final URI to generate the cache key. You can configure multiple URI replacement rules. DCDN applies them in order, from top to bottom. When it matches an Source URI, DCDN uses the corresponding Final URI and stops checking further rules. Source URI: A URI that starts with a forward slash (/). It must not include the `http://` prefix or domain name. Supports PCRE regular expressions. Final URI: URI that starts with a forward slash (/) and does not include the http:// prefix or domain name.
Parameter Actions	These operations apply to query parameters in the client’s original request URL. You can Add, Delete, Modify, or Reserve parameters. The result of these operations appends to the cache key. You can configure multiple operations. DCDN applies them in order, from top to bottom. Add: Add a new query parameter to the cache key. For example, if the original URL is `http://image.example.com/cat.jpg` and you add `type=jpg`, the cache key becomes `http://image.example.com/cat.jpg?type=jpg`. Delete: Remove a specified query parameter from the original URL when generating the cache key. For example, if the original URL is `http://image.example.com/cat.jpg?type=jpg` and you delete the `type` parameter, the cache key becomes `http://image.example.com/cat.jpg`. Modify: Modify the specified parameter in the original request URL when generating the cache key. For example, if the original URL is `http://image.example.com/cat.jpg?type=jpg` and you modify the parameter to `type=png`, the cache key is. Reserve: Keep only specified query parameters from the original URL when generating the cache key. For example, if the original URL is `http://image.example.com/cat.jpg?type=jpg&path=image` and you keep only the `type` parameter, the cache key becomes `http://image.example.com/cat.jpg?type=jpg`.
HTTP Headers	Append the value of a specified HTTP header from the client’s original request to the cache key. You can specify multiple HTTP header names, separated by spaces. DCDN appends their values to the cache key in order. For example, if the original URL is `http://image.example.com/cat.jpg` and the client sends an HTTP header `path:image`, and you set `path` in the HTTP Headers configuration, the cache key becomes `http://image.example.com/cat.jpgimage`.
Custom Variables	Use a regular expression to match values from request parameters, HTTP headers, cookies, or URIs in the client’s original request. If the regular expression matches, append the matched value to the cache key. For details, see Configuration examples.

Click OK to complete the configuration.

Configuration examples

URIs

Requests for http://aliyundoc.com/a/b/image.jpg and http://aliyundoc.com/a/b/c/image.jpg refer to the same file. The cache key is http://aliyundoc.com/c/image.jpg. URI

Parameter Actions

The client’s request http://aliyundoc.com/a/b/image.jpg?delete_par=1&modify_par=1 adds add_par=1, deletes delete_par, and modifies modify_par to 2. The final cache key is http://aliyundoc.com/a/b/image.jpg?modify_par=2&add_par=1.

Important

In parameter operations, if you apply multiple operations to the same variable, they take effect in this order: add > delete > keep > modify.

参数操作

HTTP Headers

The values of the User-Agent and Accept-Language HTTP headers from a client request are appended to the cache key. For example, if a request for http://aliyundoc.com/a/b/image.jpg contains the headers User-Agent=Mozilla/5.0 (Linux; X11) and Accept-Language=en, the cache key for the request is http://aliyundoc.com/a/b/image.jpgMozilla/5.0(Linux;X11)en. HTTP Header

Custom Variables

Example 1

The variable name is language. Its source is the Request Header. The source field name is Accept-Language. The matching pattern is ([%w]+),([%w]+). The variable expression is $1aa. 自定义变量

For the client request http://aliyundoc.com/a/b/image.jpg with the HTTP header Accept-Language=en,ch , the pattern matches en and assigns it to $1. The variable expression appends aa, resulting in the variable value enaa. This variable, aliased as language, is then appended to the URL to form the final cache key: http://aliyundoc.com/a/b/image.jpgenaa.

Note

In a variable expression, $n refers to the content matched by the nth pair of parentheses in the matching rule. For example, in Example 1, Accept-Language=en,ch, the matching rule is ([%w]+),([%w]+). Therefore, $1=en and $2=ch.

Example 2

The variable name is expired. The source is Request Cookie. The source field name is a. The matching rule is [%w]+:(.*). The variable expression is $1. Custom variable

For the client request http://aliyundoc.com/a/b/image.jpg with the cookie Cookie a=expired_time:12635187, the pattern matches 12635187 and assigns it to $1. This variable, aliased as expired, is then appended to the URL to form the final cache key: http://aliyundoc.com/a/b/image.jpg12635187.

Example 3

Configure both URI rules and custom variables.

URI:
Match all URIs that follow the pattern /abc/.*/abc and replace them with /abc.
Custom variable:
The variable name is testname. Its source is the Path. The matching pattern is /abc/xyz/(.*). The variable expression is $1.
For the client request URL http://aliyundoc.com/abc/xyz/abc/image.jpg, the URI rule modifies the cache key to http://aliyundoc.com/abc/image.jpg. The custom variable rule then matches /abc/xyz/(.*). In this case, $1 equals abc. DCDN appends this to the modified cache key to form the final cache key: http://aliyundoc.com/abc/image.jpgabc. This combination of rules supports more complex caching logic.
If no custom variable matches, DCDN does not append the variable expression $1 to the cache key.