CEL Rule Engine

This repository contains a configurable rule engine using CEL (Common Expression Language) for flexible business logic and validation.

Features

• YAML-based configuration for rules, rulesets, execution policies, and environment overrides
• CEL expressions for powerful, type-safe rule logic
• Customizable error handling and logging
• Environment-specific overrides for development and production

Example: Defining Rules

Rules are defined in rules.yml under the rules: section.
Example:

rules:
  age_validation:
    name: "Age Validation"
    description: "Validates user age requirements"
    expression: "user.age >= globals.min_age"

  email_format:
    name: "Email Format Check"
    description: "Validates email format using regex"
    expression: |
      user.email.matches("^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,}$")

Example: Combining Rules

Rulesets allow you to combine multiple rules using logical operators:

rulesets:
  user_registration:
    name: "User Registration Validation"
    description: "All rules must pass for successful registration"
    combination_type: "AND" # OR is allowed, default is AND
    rules:
      - age_validation
      - email_format
      - user_status

Execution Policies

Control how rules are executed:

execution_policies:
  fail_fast:
    name: "Fail Fast Execution"
    stop_on_failure: true

  collect_all:
    name: "Collect All Results"
    stop_on_failure: false
    collect_errors: true

Error Handling

Customize error handling and logging:

error_handling:
  execution_policy: "collect_all"
  custom_error_messages:
    age_validation: "User must be at least 18 years old"
    email_format: "Please provide a valid email address"
    domain_whitelist: "Email domain is not allowed"
    business_hours: "Service only available during business hours (9 AM - 5 PM)"

Environment Overrides

Override globals and policies per environment:

environments:
  development:
    globals:
      min_age: 13 # Lower age requirement for testing

  production:
    globals:
      min_age: 18
    error_handling:
      default_policy: "fail_fast"

Usage

To use the rule engine, load the configuration from rules.yml, set up the environment cel.Env, and evaluate rules against input data context.

For more details, see the comments in rules.yml or consult the CEL documentation.

Performance

Using approximately 600 rules and 300 rulesets

goos: darwin
goarch: arm64
pkg: github.com/mobanhawi/ruleengine
cpu: Apple M1 Pro
BenchmarkRuleEngine_EvaluateAllRulesets
BenchmarkRuleEngine_EvaluateAllRulesets-8           	     601	   1902203 ns/op
BenchmarkNewRuleEngine
BenchmarkNewRuleEngine-8                            	      30	  39444917 ns/op
BenchmarkRuleEngineOptimise_EvaluateAllRulesets
BenchmarkRuleEngineOptimise_EvaluateAllRulesets-8   	    2580	    462594 ns/op
BenchmarkNewRuleEngineOptimise
BenchmarkNewRuleEngineOptimise-8                    	      28	  40634042 ns/op