Implement API Gateway Service Routing - Proxies

Implementation

An API Gateway provides a unified entry point for multiple microservices. Clients make one request to the gateway, which routes to the appropriate backend service.

Gateway architecture:

Clients → API Gateway → Microservices
  - /api/users/*    → users-service (3 instances)
  - /api/orders/*   → orders-service (2 instances)
  - /api/products/* → products-service (4 instances)
  - /api/payments/* → payments-service (2 instances)

Routing rules:

{
  "routes": [
    {
      "path_pattern": "/api/users/*",
      "service": "users-service",
      "version": "v1",
      "backends": ["users-1:8080", "users-2:8080", "users-3:8080"],
      "strip_prefix": false
    },
    {
      "path_pattern": "/api/v2/users/*",
      "service": "users-service",
      "version": "v2",
      "backends": ["users-v2-1:8080", "users-v2-2:8080"],
      "strip_prefix": false
    },
    {
      "path_pattern": "/api/orders/*",
      "service": "orders-service",
      "version": "v1",
      "backends": ["orders-1:8080", "orders-2:8080"],
      "strip_prefix": false
    }
  ]
}

Example gateway routing:

// Request to gateway:
Request:  {"type": "api_request", "msg_id": 1, "method": "GET", "path": "/api/users/123", "headers": {"Host": "api.example.com"}}
Response: {"type": "api_response", "in_reply_to": 1, "status": 200, "service": "users-service", "backend": "users-1", "body": "{"id": 123, "name": "Alice"}"}

// Request with versioning:
Request:  {"type": "api_request", "msg_id": 2, "method": "GET", "path": "/api/v2/users/123", "headers": {"Host": "api.example.com"}}
Response: {"type": "api_response", "in_reply_to": 2, "status": 200, "service": "users-service", "backend": "users-v2-1", "body": "{"id": 123, "name": "Alice", "email": "alice@example.com"}"}

Sample Test Cases

Route to correct serviceTimeout: 5000ms

Input

{"src":"client","dest":"gateway","body":{"type":"init","msg_id":1,"routes":[{"path_pattern":"/api/users/*","service":"users-service","backends":["users-1","users-2"]}]}}
{"src":"client","dest":"gateway","body":{"type":"api_request","msg_id":2,"method":"GET","path":"/api/users/123"}}

Expected Output

{"src": "gateway", "dest": "client", "body": {"type": "init_ok", "in_reply_to": 1}}

Service versioningTimeout: 5000ms

Input

{
  "src": "client",
  "dest": "gateway",
  "body": {
    "type": "api_request",
    "msg_id": 1,
    "method": "GET",
    "path": "/api/v2/users/123"
  }
}

Expected Output

{"src": "gateway", "dest": "client", "body": {"type": "api_response", "in_reply_to": 1, "status": 200, "service": "users-service", "version": "v2"}}

Hints

Hint 1▾

API gateway provides unified entry point for multiple microservices

Hint 2▾

Route requests to backend services based on URL patterns

Hint 3▾

Example: /api/users/* → users-service, /api/orders/* → orders-service

Hint 4▾

Support service versioning: /api/v1/users vs /api/v2/users

Hint 5▾

Handle service discovery: dynamically resolve service instances

Implementation

Sample Test Cases

Hints

Resources

Theoretical Hub

Key Concepts