ESA employs rules as its core. You can configure rules using general syntax rules and filter conditions for features.
Before you begin
If you configure a feature using both rule and global settings, the rule takes precedence for matching incoming requests.
The length of a single rule configuration (including the rule condition and feature configuration) can be up to 4 KB in size.
All configuration information, including global settings and rules, must not exceed a total size of 512 KB (excluding security rules).
The rule name must be 1 to 128 characters in length.
Rule structure
In ESA, a rule usually consists of a rule expression and an action.
Rule expression
Specifies the filter conditions for your request. A condition is composed of a match field, match operator, and match value.
In the ESA console, the If requests match... section lists rule expressions. By default, is selected for you to quickly configure filter conditions.
You can also select All Requests to apply the rule to all requests.
In the ESA console, you can also directly edit expressions.
Action
Specifies the action you want to take on requests that meet the filter conditions.
In the Then execute... section in the ESA console, you can set up rules for desired features.
Filter conditions
For a single expression
Sometimes, a single filter condition may not be enough. The ESA rules support combining multiple conditions, using the following logical relationships:
AND: Click
to create an AND logical relationship. The following figure shows a rule expression, where the hostname and country/region are
example-1.comand Chinese mainland, respectively.OR: Click
to create an OR logical relationship. The following figure shows a rule expression, where the hostname is
example-1.comorexample-2.com.
The maximum number of conditions allowed in a rule expression depends on your plan type. For example, an Enterprise plan supports up to 20 conditions in a single expression.
For a nested expression
The ESA rules support nesting AND logical relationships within an OR relationship.
For example, you can set the following filter conditions:
The hostname is
example-1.com.Or the hostname is
example-2.comand the country/region is not the Chinese mainland.Or the hostname is
example-3.com.
Expression builder
In addition to graphical controls, ESA also provides an expression builder for configuring rule expressions via code.
Preview an expression
After you configure a rule expression using graphical controls, ESA automatically generates it in code format.
Single expression: (<Match field> <Match operator> <Match value>)
Example: (http.host eq "example-1.com")
Nested expression: (<Single expression 1> <Nested logical operator> <Single expression 2>)
Example: (http.host eq "example-1.com" and http.host eq "example-2.com")
Edit an expression
Click Edit Expression to directly edit a rule expression.