request-callout

Request Callout Example

This example demonstrates how to use Kong's Request Callout plugin to enrich API requests with data from multiple backend services.

Overview

The setup includes:

• A main service that receives requests and enriches them with user and address data
• A mock service that simulates user and address backend APIs
• Two callouts that fetch data sequentially (user data first, then address data)

Prerequisites

• Docker
• Docker Compose
• Kong Enterprise license (for the Request Callout plugin)

Setup

1. Start the Kong Gateway:

docker compose up -d

2. Verify the services are running:

curl localhost:8001/services

Testing the Setup

Send a request with a user ID:

curl -X POST http://localhost:8000 \
  -H "Host: callout.dev" \
  -H "Content-Type: application/json" \
  -d '{"id": "123"}'

Expected response:

{
  "username": "John Doe",
  "country": "USA"
}

How It Works

1. When a request arrives with a user ID, the first callout (c1) fetches user data:

   • Calls /v1/users/{id}
   • Returns user information including username and address_id

2. The second callout (c2) uses the address_id from the first callout:

   • Calls /v1/addresses/{id}
   • Returns address information including country

3. The final response combines:

   • Username from the first callout
   • Country from the second callout

Mock API

The example includes a mock API (using Kong's Mocking plugin) that simulates two backend services:

• User Service (/v1/users/{id}):

  • Returns user details including username and address_id
  • Example users: 123 (John Doe), 124 (Jane Smith)

• Address Service (/v1/addresses/{id}):

  • Returns address details including country
  • Example addresses: 456 (USA), 457 (Germany)

Configuration Files

• kong-config/kong.yaml: Main Kong configuration including services, routes, and plugins
• mock-api.yaml: OpenAPI specification for the mock backend services
• docker-compose.yaml: Docker Compose configuration for running Kong

Additional Notes

• The Request Callout plugin requires Kong Enterprise
• The mock service runs on the same Kong instance using the Mocking plugin
• Callouts are executed sequentially, with c2 depending on the response from c1