DCDN rules engine-Edge Security Acceleration(ESA)-阿里云帮助中心

Use the rules engine's graphical interface to define conditional rules based on request parameters and control exactly when DCDN configuration policies take effect.

Note

Note: When this feature references rule conditions from the Rules Engine, the execution order follows the priority order of the rule conditions configured in the Rules Engine, NOT the priority order of this feature's own configuration.

Background

The Alibaba Cloud DCDN console provides basic features such as configuring time-to-live (TTL) and rewriting back-to-origin parameters. These features cover most use cases but cannot handle all requirements. For example, you might need to route requests containing the path /example to a specific origin. For such scenarios, combine basic features with the rules engine for more flexible configurations. Alibaba Cloud DCDN also offers EdgeRoutine for advanced customization.

Configuration capability	Basic features	Basic features + rules engine	EdgeRoutine
Implementation	General-purpose configurations	Flexible custom configurations	Highly flexible custom configurations
Scenarios	Common use cases	Advanced custom requirements	Fully customized requirements
Difficulty	Low	Medium	High
Configuration flexibility	Low	Medium	High

Limitations

You can create a maximum of 50 rule conditions per domain name.
Each rule condition can contain a maximum of 20 sub-rules.
You cannot use regular expression match or regular expression mismatch operators when configuring rule conditions in the console or using OpenAPI. However, you can view existing configurations that use these operators. To use these operators, use ESA.
A rule condition can be referenced a maximum of five times across all features within a single domain name.
You can nest rule conditions up to three levels deep, and each level can have its own independent logical relationships.
If a feature, such as setting the cache expiration time or modifying outgoing request headers, references a rule condition, the condition's priority determines the execution order, not the feature's configuration order.
Among the preceding limits, the maximums of 50 rule conditions, 20 sub-rules, and 3 levels of nesting are hard limits that cannot be increased upon request. The maximum total number of references to rule conditions across all features within a single accelerated domain name, which is 5 by default, can be increased upon request.
- To increase the total number of times that rule conditions can be referenced for a single domain name (five by default), submit a ticket. Provide the following information in the ticket: the accelerated domain name for which you want to increase the limit, the target number of references, and a description of your business scenario.
- When adding another accelerated domain name, submit a separate ticket to increase the number of rule-condition references for that domain. The process is the same as for the first request.
Each condition can have a maximum of 32 match values for match types such as client IP, URI, file extension, filename, and User-Agent. If you have a large client IP allowlist, consolidate multiple IP addresses into CIDR blocks (for example, 120.209.XXX.X/24) to configure the IP addresses and conserve match-value capacity.
You can configure a maximum of 32 User-Agent match values. Values beyond this limit are ignored. To match a large number of User-Agents, use a wildcard (*) to consolidate similar User-Agent values. For example, *Chrome* matches all Chrome browser versions), or use EdgeScript for more flexible matching logic.

Rule condition syntax

A rule condition combines one or more conditional expressions by using logical operators. The following sections describe the syntax.

Logical operators

Logical operators evaluate conditions at the same level, including nested condition sets. The supported operators are and and or.

and (AND): A logical AND operator. A match succeeds only if all conditions are true.
or (OR): A logical OR operator. A match succeeds if any condition is true. For example, configuring multiple rule conditions for the same response header lets you add the same response header under different conditions. Example: When the URI contains /path-a or the URI contains /path-b , add the response header.

Parameters of a conditional expression

A conditional expression, the most granular unit of a rule, includes the following parameters:

Parameter	Corresponding configuration parameter in the condition function for domain name configuration	Description	Required
Conditional match	match	Specifies the conditional match expression.	Yes
Logical operator	logic	Specifies the logical operator for the conditional match expression. Valid values are `and` and `or`.	Yes
Criteria	criteria	Specifies the array of conditional expressions to be evaluated.	Yes
Match type	MatchType	Specifies the type of information in a client request to match.	Yes
Match object	MatchObject	Further refines the match type. For example, a client IP address can be specified as a POP connection IP or an XFF IP.	No
Match operator	MatchOperator	Specifies the comparison to perform.	Yes
Match value	MatchValue	The value to compare against data from the client request.	Yes
Negate condition	negate	Specifies whether to negate the result of the conditional expression. Valid values are true and false.	Yes
Case sensitivity	caseSensitive	Specifies whether the match value is case-sensitive.	No
Rule condition name	name	Specifies the name of the rule condition.	Yes
Status	status	Specifies the status of the rule condition.	Yes

Features supporting rule conditions

Feature category	Feature name
origin fetch configuration	Specify the origin host
	Modify incoming request headers
	origin HTTP request headers (New)
	origin HTTP response headers
cache configuration	Configure time-to-live
	Modify outgoing response headers
	custom cache key

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 Actions column.
In the left navigation pane, click Rule Engine.
Click Create Rule.
On the Create Rule page, set the Rule Name and Rule Content.
Click Submit.