Online Order Rule Engine with n8n

🚀 Overview

This project is an online ordering system that uses .NET Core Web API and SQL Server, with n8n acting as the Rule Engine. The Rule Engine evaluates customer and product eligibility based on their scores, approving or rejecting orders based on whether they meet the criteria.

🔧 Architecture

1. .NET Core Web API
   • Manages incoming order requests and provides endpoints to fetch customer and product data.
2. SQL Server
   • Stores customer and product scores.
3. n8n Rule Engine
   • Validates whether an order should be approved or rejected based on the scores retrieved from the API.

⚙️ How It Works

1. A customer places an order via the .NET Core API.
2. The order is sent to n8n for rule evaluation.
3. n8n fetches:
   • Customer Score from the API endpoint:

     GET /users/{id}

   • Product Score from the API endpoint:

     GET /product/{id}

4. n8n compares both scores:
   • If the customer score is greater than or equal to the product score threshold → Order Approved
   • If the scores don’t match → Order Rejected
5. The decision is sent back to the .NET API, which updates the order status in SQL Server.

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🔄 n8n Workflow Implementation

1. Trigger the Workflow:
   • A Webhook Node receives the order details from the .NET API.
2. Fetch Customer & Product Scores:
   • Use HTTP Request Nodes to call /users/{id} to retrieve customer_score.
   • Use HTTP Request Nodes to call /product/{id} to retrieve product_score_threshold.
3. Decision Making:
   • The IF Node compares customer_score with product_score_threshold.
   • If the customer score meets the threshold, the order is approved; if not, it is rejected.
4. Respond to Webhook:
   • If approved → Update the order status to "Confirmed" in the .NET API.
   • If rejected → Update the order status to "Rejected" in the .NET API.

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⚖️ Example Rule Logic

IF customer_score >= product_score_threshold THEN
    Approve order
ELSE
    Reject order

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🛠️ Technology Stack

• Backend: .NET Core Web API
• Database: SQL Server
• Rule Engine: n8n
• Workflow Automation: n8n Nodes (Webhook, HTTP Request, IF Condition)

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📝 Setup Instructions

1. Docker Configuration for n8n

• The Docker configurations for n8n are located in the docker folder.
• Set up necessary environment variables and volume mappings in the configuration files.
• Use the following command to start the setup:

  docker-compose up -d

  This will bring up n8n with all the required configurations.

2. Setup .NET Core API

• Clone the repository and configure the SQL Server connection string.
• Run database migrations to create tables for customers, products, and orders.
• Make sure the following endpoints are set up in the API:
  • GET /users/{id} → Returns customer score.
  • GET /product/{id} → Returns product score threshold.
  • PATCH /orders/{id} → Updates the order status.

3. Deploy n8n

• Use Docker or install n8n locally:
• Create a Webhook Trigger in n8n to listen for order requests.
• Use HTTP Request Nodes to fetch customer and product scores.
• Implement the workflow to compare scores and respond back to the .NET API.

4. Test the Integration

• Place an order via the .NET Core API.
• Verify the order status in SQL Server.
• Monitor n8n executions to confirm that the rule engine is functioning as expected.

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🔧 WorkFlow Example for n8n

Here's the JSON file for the n8n workflow. Copy and paste it into n8n to run it:

{
  "nodes": [
    {
      "parameters": {
        "httpMethod": "POST",
        "path": "RuleEngine",
        "responseMode": "responseNode",
        "options": {}
      },
      "type": "n8n-nodes-base.webhook",
      "typeVersion": 2,
      "position": [
        -180,
        180
      ],
      "id": "77be25d3-2fea-417a-9933-b0ab495142cb",
      "name": "Webhook",
      "webhookId": "cab59b31-26f8-493a-b68f-a08fcd5db279"
    },
    {
      "parameters": {
        "url": "=http://192.168.11.18:5000/products/{{$json.body.productId}}",
        "options": {}
      },
      "type": "n8n-nodes-base.httpRequest",
      "typeVersion": 4.2,
      "position": [
        60,
        -100
      ],
      "id": "e8aa5627-1442-47b6-a9dd-57f9530ed339",
      "name": "Get Product"
    },
    {
      "parameters": {
        "url": "=http://192.168.11.18:5000/users/{{$('Webhook').item.json.body.userId}}",
        "options": {}
      },
      "type": "n8n-nodes-base.httpRequest",
      "typeVersion": 4.2,
      "position": [
        280,
        180
      ],
      "id": "2ab2f920-b880-4530-ba5c-591fc5783014",
      "name": "Get User"
    },
    {
      "parameters": {
        "conditions": {
          "options": {
            "caseSensitive": true,
            "leftValue": "",
            "typeValidation": "strict",
            "version": 2
          },
          "conditions": [
            {
              "id": "5f3dcb94-147e-487d-b8c6-c4189be03541",
              "leftValue": "={{ $('Get Product').item.json.limitBonus }}",
              "rightValue": "={{ $json.bonus }}",
              "operator": {
                "type": "number",
                "operation": "gt"
              }
            }
          ],
          "combinator": "and"
        },
        "options": {}
      },
      "type": "n8n-nodes-base.if",
      "typeVersion": 2.2,
      "position": [
        520,
        180
      ],
      "id": "651b2eba-6c8e-4475-b013-8dc8520839a9",
      "name": "Check For Bonus"
    },
    {
      "parameters": {
        "conditions": {
          "options": {
            "caseSensitive": true,
            "leftValue": "",
            "typeValidation": "strict",
            "version": 2
          },
          "conditions": [
            {
              "id": "85d7d2c5-7c95-4faf-b30f-ff42a3358366",
              "leftValue": "={{ $json.verified }}",
              "rightValue": "",
              "operator": {
                "type": "boolean",
                "operation": "true",
                "singleValue": true
              }
            }
          ],
          "combinator": "and"
        },
        "options": {}
      },
      "type": "n8n-nodes-base.if",
      "typeVersion": 2.2,
      "position": [
        740,
        280
      ],
      "id": "37fb92d3-3812-44b8-8beb-c313b8f56862",
      "name": "Check For Verified User"
    },
    {
      "parameters": {
        "respondWith": "json",
        "responseBody": "{\n  \"Response\": \"Ok\"\n}",
        "options": {}
      },
      "type": "n8n-nodes-base.respondToWebhook",
      "typeVersion": 1.1,
      "position": [
        1120,
        180
      ],
      "id": "8d4e0db8-f583-4b6f-a407-0d039796ee8b",
      "name": "Ok"
    },
    {
      "parameters": {
        "respondWith": "json",
        "responseBody": "{\n  \"Response\": \"To purchase from our business, the user must be verified.\"\n}",
        "options": {}
      },
      "type": "n8n-nodes-base.respondToWebhook",
      "typeVersion": 1.1,
      "position": [
        1020,
        500
      ],
      "id": "ae1be130-26ff-4053-9912-74edc01eb47d",
      "name": "Error For User Not Verify"
    },
    {
      "parameters": {
        "respondWith": "json",
        "responseBody": "{\n  \"Response\": \"You Have Does Not Enought Of Bonus For Buy This Product\"\n}",
        "options": {}
      },
      "type": "n8n-nodes-base.respondToWebhook",
      "typeVersion": 1.1,
      "position": [
        780,
        -40
      ],
      "id": "3ae0c3ab-ecff-4a4e-b274-1c221d8ac511",
      "name": "Error For User Bouns Balance"
    }
  ],
  "connections": {
    "Webhook": {
      "main": [
        [
          {
            "node": "Get Product",
            "type": "main",
            "index": 0
          }
        ]
      ]
    },
    "Get Product": {
      "main": [
        [
          {
            "node": "Get User",
            "type": "main",
            "index": 0
          }
        ]
      ]
    },
    "Get User": {
      "main": [
        [
          {
            "node": "Check For Bonus",
            "type": "main",
            "index": 0
          }
        ]
      ]
    },
    "Check For Bonus": {
      "main": [
        [
          {
            "node": "Error For User Bouns Balance",
            "type": "main",
            "index": 0
          }
        ],
        [
          {
            "node": "Check For Verified User",
            "type": "main",
            "index": 0
          }
        ]
      ]
    },
    "Check For Verified User": {
      "main": [
        [
          {
            "node": "Ok",
            "type": "main",
            "index": 0
          }
        ],
        [
          {
            "node": "Error For User Not Verify",
            "type": "main",
            "index": 0
          }
        ]
      ]
    }
  },
  "pinData": {}
}

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🚀 Future Enhancements

• Implement Caching: Reduce API calls for improved performance.
• Dynamic Pricing & Fraud Detection: Add more complex rules to improve the decision-making process.
• Real-Time Order Processing: Integrate a messaging system like RabbitMQ or Kafka for real-time updates.