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Overview

This endpoint demonstrates KrakenD’s powerful aggregation and transformation capabilities by combining data from multiple GitHub API endpoints into a single response. HTTP Method: GET
Endpoint: /git/{user}

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Parameters

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user
string
required
The GitHub username to fetch data for (e.g., “octocat”)

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What It Demonstrates

  • Aggregation: Combines data from two separate GitHub API calls
  • Field Filtering: Uses allow to return only specific fields
  • Field Mapping: Renames fields (e.g., blog → website)
  • Grouping: Organizes user profile data under a user object
  • Collection Handling: Properly handles the repositories array

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Request Example

curl http://localhost:8080/git/octocat

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Expected Response

{
  "user": {
    "avatar_url": "https://avatars.githubusercontent.com/u/583231?v=4",
    "name": "The Octocat",
    "company": "@github",
    "website": "https://github.blog",
    "location": "San Francisco",
    "mail": null,
    "hireable": null,
    "followers": 5000,
    "public_repos": 8,
    "public_gists": 8
  },
  "repos": [
    {
      "id": 1296269,
      "name": "Hello-World",
      "full_name": "octocat/Hello-World",
      "description": "My first repository on GitHub!",
      "stargazers_count": 1500,
      "language": "JavaScript"
    }
  ]
}

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Backend Services Called

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1. GitHub User Profile

  • Host: https://api.github.com
  • URL Pattern: /users/{user}
  • Purpose: Fetches user profile information
  • Group: user
Allowed Fields:
  • avatar_url
  • name
  • company
  • blog (mapped to website)
  • location
  • mail
  • hireable
  • followers
  • public_repos
  • public_gists

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2. GitHub User Repositories

  • Host: https://api.github.com
  • URL Pattern: /users/{user}/repos
  • Purpose: Fetches user’s public repositories
  • Collection: Mapped to repos field

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KrakenD Configuration

{
  "@comment": "Feature: Aggregation + Basic transformation (filtering & mapping) + grouping",
  "endpoint": "/git/{user}",
  "backend": [
    {
      "host": ["https://api.github.com"],
      "url_pattern": "/users/{user}",
      "allow": [
        "avatar_url",
        "name",
        "company",
        "blog",
        "location",
        "mail",
        "hireable",
        "followers",
        "public_repos",
        "public_gists"
      ],
      "mapping": {
        "blog": "website"
      },
      "group": "user"
    },
    {
      "host": ["https://api.github.com"],
      "url_pattern": "/users/{user}/repos",
      "mapping": {
        "collection": "repos"
      },
      "is_collection": true
    }
  ]
}

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Key Configuration Options

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allow

Filters the backend response to include only the specified fields. This reduces payload size and prevents exposing unnecessary data.

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mapping

Transforms field names in the response. In this example, GitHub’s blog field becomes website in the API response.

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group

Nests the backend response under a specific key. The user profile data is grouped under user to organize the aggregated response.

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is_collection

Indicates that the backend returns an array. Combined with mapping, this properly handles the repositories collection.

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Use Cases

  • Developer portfolio APIs
  • GitHub integration dashboards
  • User profile aggregation services
  • Simplified GitHub API wrapper

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