If you enable parameter filtering, Alibaba Cloud CDN nodes remove the parameters (query strings) that follow the question mark (?) in request URLs. These parameters contain information such as the user identity and request source. The original URLs are used as the cache keys. This topic describes how to configure parameter filtering.

Overview

Note The URL signing feature has a higher priority over the parameter filtering feature. The signature information of authentication type A contains the parameters of an HTTP request. Therefore, Alibaba Cloud CDN verifies the signature of the request URL before the CDN nodes cache a copy of the requested resource. For information about how to configure URL signing, see Configure URL signing.
  • Ignore parameters
    Description Scenario
    Alibaba Cloud CDN removes the parameters that follow the question mark (?) in request URLs so that requests that are destined for the same file but carry different URL parameters can hit the cache. Parameter filtering increases the cache hit ratio, reduces the back-to-origin routing frequency, and accelerates file distribution. Some users append parameters after the question mark (?) in request URLs to pass information such as the user ID (UID), request source, and recommendation code to the origin server. In this case, these URLs carry different query strings even if the requests are sent to the same file.
    We recommend that you enable parameter filtering if the parameters that follow the question mark (?) in URLs are irrelevant to the requested resource. Example:
    • Request from user A: http://example.com/1.jpg?uid=123***
    • Request from user B: http://example.com/1.jpg?uid=654***
    If the CDN node uses the original URLs from user A and user B, the requests cannot hit the same file in the cache. The requests must be redirected to the origin server.

    After parameter filtering is enabled, the CDN node removes the UIDs that follow the question mark (?) in the request URLs. The final URL http://example.com/1.jpg is used to match the cache.

  • Retain parameters in back-to-origin requests
    Description Scenario
    The original URLs are redirected to the origin server so that key user information can be passed to the origin server. If you enable parameter filtering, CDN nodes redirect the URLs processed by parameter filtering to the origin server. In the preceding example, the requests from user A and user B both use the URL http://example.com/1.jpg. The UIDs are not passed to the origin server during back-to-origin routing.

    If you choose to retain parameters in back-to-origin requests, CDN nodes redirect the original URLs to the origin server so that the UIDs are passed to the origin server.

Parameter filtering can retain or remove specified parameters. The following figure shows the process of parameter filtering.Parameter filtering

Procedure

  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.
    域名管理
  4. In the left-side navigation pane of the domain name, click Optimization.
  5. In the Ignore Parameters section, click Modify. In the dialog box that appears, select a filter mode based on your business requirements and configure the parameters.
    Important If you switch to another filter mode, existing configurations are cleared.
    • Filter Mode: Retain Specified ParametersParameter filtering
      Parameter Description Example
      Ignore Parameters
      • Yes: enables parameter filtering. Parameters that follow the question mark (?) are removed from URLs.
        Note If you enable Ignore Parameters and do not specify the Retain Specified Parameters parameter, all parameters that follow the question mark (?) are removed.
      • No: disables parameter filtering.
      		If the original URL is http://example.com/1.jpg?key1=1&key2=2&key3=3, the following examples show how the URL is processed based on different settings:
      • Example 1: removes all parameters and redirects the final URL to the origin server.
        • Parameter settings: Ignore Parameters is set to Yes, no value is specified for Retain Specified Parameters, and Retain Parameters in Back-to-origin Requests is set to No.
        • Cache key: http://example.com/1.jpg.
        • URL redirected to the origin server: http://example.com/1.jpg.
      • Example 2: retains specified parameters and redirects the final URL to the origin server.
        • Parameter settings: Ignore Parameters is set to Yes, Retain Specified Parameters is set to key1, and Retain Parameters in Back-to-origin Requests is set to No.
        • Cache key: http://example.com/1.jpg?key1=1.
        • URL redirected to the origin server: http://example.com/1.jpg?key1=1.
      • Example 3: removes all parameters and redirects the original URL to the origin server.
        • Parameter settings: Ignore Parameters is set to Yes, no value is specified for Retain Specified Parameters, and Retain Parameters in Back-to-origin Requests is set to Yes.
        • Cache key: http://example.com/1.jpg.
        • URL redirected to the origin server: http://example.com/1.jpg?key1=1&key2=2&key3=3.
      • Example 4: retains specified parameters and redirects the original URL to the origin server.
        • Parameter settings: Ignore Parameters is set to Yes, Retain Specified Parameters is set to key1, and Retain Parameters in Back-to-origin Requests is set to Yes.
        • Cache key: http://example.com/1.jpg?key1=1
        • URL redirected to the origin server: http://example.com/1.jpg?key1=1&key2=2&key3=3.
      Retain Specified Parameters You can specify up to 10 parameters that you want to retain. Separate multiple parameters with commas (,).
      Retain Origin Parameters
      • Yes: retains all parameters in URLs during back-to-origin routing.
      • No: retains only specified parameters in URLs during back-to-origin routing. The parameters remain the same as those in the cache key.
    • Filter Mode: Remove Specified ParametersRemove specified parameters
      Parameter Description Example
      Remove Specified Parameters You can specify up to 10 parameters that you want to remove. Separate multiple parameters with commas (,). If the original URL is http://example.com/1.jpg?key1=1&key2=2&key3=3, the following examples show how the URL is processed based on different settings:
      • Example 1: removes specified parameters and redirects the final URL to the origin server.
        • Parameter settings: Remove Specified Parameters is set to key1, and Retain Parameters in Back-to-origin Requests is set to No.
        • Cache key: http://example.com/1.jpg?key2=2&key3=3.
        • URL redirected to the origin server: http://example.com/1.jpg?key2=2&key3=3.
      • Example 2: removes specified parameters and redirects the original URL to the origin server.
        • Parameter settings: Remove Specified Parameters is set to key1, and Retain Parameters in Back-to-origin Requests is set to Yes.
        • Cache key: http://example.com/1.jpg?key2=2&key3=3.
        • URL redirected to the origin server: http://example.com/1.jpg?key1=1&key2=2&key3=3.
      Retain Origin Parameters
      • Yes: retains all parameters in URLs during back-to-origin routing.
      • No: removes only specified parameters in URLs during back-to-origin routing. The parameters remain the same as those in the cache key.
  6. Click OK.