CDN:Configure a conditional origin

Usage notes

• Feature conflict: The conditional origin and advanced origin features are mutually exclusive. You can enable only one.

• Wildcard support: In the rules engine, the URI match value supports the wildcard * (matches any number of characters) and ? (matches any single character). Path matching in the advanced origin feature supports only exact values, not wildcards.

• Rule priority and matching order: Conditional origins are evaluated based on the priority of the associated Rule Condition in the rules engine, not the order of the conditional origin configurations. When a request matches a rule, evaluation stops. Rule priority in the rules engine is determined by creation order: rules created earlier have higher priority. To adjust the matching priority, you must delete and recreate the rules in the desired order.

• Multi-path configuration tip: When creating rules to "include" or "exclude" a path, you can enter multiple paths (in multiple lines or as multiple values) in the match value field of a single rule to simplify your configuration.

• Rule limit: The number of Rule Conditions that a conditional origin can reference is subject to a global limit in the rules engine. For a single domain, the total number of references to Rule Conditions across all features, including conditional origin, advanced origin, and Referer-based hotlink protection, cannot exceed five. In complex multi-origin scenarios, exceeding this limit causes the configuration to fail. We recommend that you plan your rule usage carefully or use separate domains for acceleration if you have many origins.

Considerations for OSS origins

• If an origin is an OSS bucket, you must add its address under Domain Names > Basics > Origin Information and set the origin type to OSS Domain. This enables CDN to authenticate correctly with OSS.

• Multi-OSS origin scenarios: When you configure multiple OSS origins, you must configure a specific origin Host for each one. The Host value must exactly match the corresponding OSS bucket domain, such as dev-3mir.oss-cn-guangzhou.aliyuncs.com.

  If the origin Host is not configured correctly or if you rely on the default origin Host, requests may be routed to the wrong bucket. This can cause 403 SignatureDoesNotMatch or 404 Not Found errors. You must explicitly bind every conditional origin rule, including match rules and fallback rules, to its corresponding origin and origin Host. When you configure multiple origins, we recommend setting equal weights for the basic origins and creating separate Rule Conditions for each conditional origin to ensure predictable routing.

Origin type comparison

Both conditional origins and advanced origins can reference Rule Conditions from the rules engine to create flexible origin routing policies. CDN automatically selects an origin if a request matches a Rule Condition:

Procedure

1. Log on to the CDN console.

2. In the left navigation pane, click Domain Names.

3. On the Domain Names page, find the target domain name and click Manage in the Actions column.

4. In the Origin Information section, click Expand next to Conditional Origin.

5. Click Add Conditional Origin.

6. Set the Rule Condition.

   • If this is your first time adding a configuration or you need to modify an existing Rule Condition, click Conditional Origin in the Rules Engine dialog box. This opens the rules engine where you can add or modify configurations. For more information, see rules engine.

   • If you have an existing Rule Condition, select it from the Rule Condition drop-down list.

7. In the Origin Address field, enter the origin address. The origin address can be an IP address, a domain name, an OSS bucket, or a Function Compute (FC) endpoint.

8. Click OK to complete the configuration.

Example: Routing /api/* requests to FC

Example: Referer-based routing

The following example shows how to route requests to different origins based on the Referer header. This is useful for hotlink protection or for controlling access based on the source of the request.

Example: Cookie-based routing

The following example shows how to route requests to different origins based on the value of a cookie in the request. This is useful for A/B testing or canary release scenarios.

Example: Routing users from the Chinese mainland and outside the Chinese mainland to different origins

The following example shows how to use conditional origins with the rules engine to route users from Chinese mainland and outside Chinese mainland to different origin servers.

1. Log on to the CDN console. On the Domain Names page, find the target domain and click Manage in the Actions column. In the left navigation pane, click Rules Engine, and then click Add Rule.

2. Configure the Chinese mainland rule: In the rule content area, click the plus icon to add a match condition. Set Match type to IP Location, Match operator to Include Any and click Modify to select Chinese mainland from the drop-down list as the match value. Submit and save the rule.

3. Configure the overseas rule (fallback): Create another rule. Set Match type to IP Location, Match operator to Exclude Any, and set the match value to Chinese mainland. Submit and save the rule.

4. Configure the conditional origin: In the Origin Information section, associate each rule with its corresponding origin:

   • Associate the Chinese mainland rule with a domestic origin (for example, a domestic OSS bucket or a domestic server).

   • Associate the overseas rule with an overseas origin (for example, an overseas OSS bucket or an overseas server).

5. Configure the origin Host: Configure a dedicated Origin Host for each origin to ensure the Host value matches the corresponding origin domain.

   • In the left navigation pane of the domain management page, go to Origin Fetch > Configurations tab. In the Specify Origin Host section, click Add.

   • In the Specify Origin Host dialog box, configure the following parameters. Add one entry for each origin:

   Parameter	Value
   Origin Type	Custom origin. The origin addresses configured in conditional origins do not appear in the Basic origin address drop-down list. You must select Custom origin and manually enter the address. If the origin address is already added in the basic origin configuration (for example, as an OSS origin), you can also select Basic origin address and choose it from the drop-down list.
   Origin Address	Enter the origin address associated with the conditional origin (for example, the domain of the domestic or overseas OSS bucket).
   Origin Host Type	Custom origin Host
   Origin Host	Enter the Host value that matches the origin domain (for example, bucket.oss-cn-hangzhou.aliyuncs.com).
   Rule Condition	Select the rule condition that corresponds to this origin (for example, the Chinese mainland rule or the rule for outside the Chinese mainland).

   Click OK to complete the configuration.

You do not need to disable the default origin Host. When the default origin Host and the origin Host for a specific origin are configured for the same origin, the origin Host for the specific origin takes effect. For origins that do not have a specific origin Host configured, the default origin Host remains in effect.