Feature/graphql API Integration with Strawberry

[OJEM22]

Description

Implements a comprehensive GraphQL API for querying GTFS transit data using Strawberry GraphQL. This provides a modern, flexible alternative to the REST API with support for nested queries, field selection, pagination, and geographic search. The implementation includes 8 GraphQL types covering all major GTFS entities, 20+ query resolvers, comprehensive documentation (750+ lines), demo queries, and a full test suite (219 lines).

Type of Change

• New feature (MINOR)
• Bug fix (PATCH) - Fixed app naming conflict
• Documentation update

Transportation Context

• GTFS data handling
• Data analysis enhancement
• API endpoint modification

Testing

• Unit tests added/updated - gql/tests.py (219 lines)
• Integration tests pass - GraphQL queries tested end-to-end
• Manual testing completed - GraphiQL interface tested with multiple query patterns

Test Execution:

python manage.py test gql

Test Coverage:

• ✅ Query execution validation
• ✅ Schema structure tests
• ✅ Endpoint accessibility tests
• ✅ GTFS model fixtures
• ✅ Error handling tests
• ✅ Pagination functionality tests

Documentation

• Code comments updated
• API documentation updated - Complete gql/README.md (750+ lines)
• README.md updated - Added GraphQL API section with quick example
• CHANGELOG.md updated - Comprehensive entry following Keep a Changelog format

TRL Impact

Current TRL: 6 → New TRL: 6 (no change)

Justification: This feature adds a new API interface but does not fundamentally change the system's technology readiness level. The GraphQL API provides an alternative query interface to existing GTFS data without modifying core transit data processing capabilities. While it enhances developer experience and query flexibility, it represents an incremental improvement rather than a readiness level advancement.

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Detailed Changes

New Features

GraphQL API (/gql/ endpoint)

• Modern GraphQL Interface: Alternative to REST API with enhanced query capabilities
• Interactive GraphiQL: Browser-based visual query builder for API exploration
• 8 GraphQL Types: GTFSProvider, Agency, Stop, Route, Trip, StopTime, Calendar, GeoShape
• 20+ Query Resolvers: Multiple access patterns for flexible data retrieval
  • Basic entity lookups by ID
  • Paginated list queries
  • GTFS code-based lookups
  • Geographic proximity search (stopsNear)
  • Filtered queries by relationships
• Pagination: Connection pattern with PageInfo metadata (totalCount, hasNextPage, pageNumber, numPages)
• Nested Queries: Single-request retrieval of related data (e.g., routes → trips → stops)
• Geographic Search: PostGIS spatial queries for finding stops within radius
• Performance Optimization: ORM query optimization with select_related() and prefetch_related()
• Self-Documenting: GraphQL introspection for automatic documentation

Documentation

• gql/README.md (750+ lines)

  • Complete API reference
  • Query examples for all resolvers
  • Integration examples (Python, JavaScript, cURL)
  • Performance optimization guidelines
  • GraphQL vs REST comparison
  • Troubleshooting guide
  • Architecture documentation

• gql/DEMO_QUERIES.md

  • Curated real-world query examples
  • Basic to advanced patterns
  • Geographic search demos
  • Complex nested query examples

• CHANGELOG.md (NEW)

  • Created following Keep a Changelog format
  • Comprehensive GraphQL feature documentation
  • Technical implementation details
  • Future enhancements section

• README.md Updates

  • New GraphQL API section with quick example
  • Updated Application Structure
  • Updated Project Structure

Test Suite

• gql/tests.py (219 lines)
  • Comprehensive test coverage
  • Query execution validation
  • Schema structure tests
  • Endpoint accessibility tests
  • GTFS model fixtures
  • Error handling tests
  • Pagination functionality tests

Technical Implementation

Schema Architecture

• gql/schema.py: Strawberry Schema definition with Query type registration
• gql/types.py (271 lines): Strawberry Django model types with field mappings, custom pagination types (Connection, PageInfo), relationship fields
• gql/queries.py (265 lines): Query resolvers optimized with Django ORM

Django Integration

• gql/apps.py: Django app configuration
• datahub/settings.py: Added gql.apps.GqlConfig to INSTALLED_APPS
• datahub/urls.py: Added GraphQL endpoint routing
• GraphiQL interface enabled in development
• ASGI/Daphne server compatibility maintained

Bug Fixes

• App Naming Conflict: Renamed graphql/ directory to gql/ to avoid import collision with Python's graphql-core library (dependency of Strawberry)

Dependencies Added

• strawberry-graphql==0.285.0 - GraphQL schema definition library
• strawberry-graphql[django]==0.285.0 - Django integration for Strawberry
• Updated uv.lock with new dependencies and dependency tree

Configuration

• GraphQL endpoint: /gql/
• GraphiQL interface accessible in browser (development mode)
• ASGI server compatible
• No additional environment variables required

Impact on System

Positive Impacts

• Enhanced Developer Experience: Modern GraphQL interface with field selection and nested queries
• Reduced API Calls: Single request can fetch related data across multiple entities
• Flexible Querying: Clients request only needed fields, reducing bandwidth
• Self-Documenting: GraphQL introspection provides automatic, accurate documentation
• Geographic Capabilities: PostGIS integration enables spatial queries
• Performance: Optimized resolvers prevent N+1 query problems

No Breaking Changes

• GraphQL API is additive - all existing REST endpoints unchanged
• Both APIs coexist and can be used independently
• No modifications to existing functionality
• Backward compatible with all clients

How to Test

Access GraphiQL Interface

# Start development environment
docker compose up

# Open browser
open http://localhost:8000/gql/

Run Test Suite

# Run all GraphQL tests
docker compose exec web python manage.py test gql

# Run with verbose output
docker compose exec web python manage.py test gql --verbosity=2

Example Queries

Basic Query:

query {
  hello {
    message
  }
}

Geographic Search:

query {
  stopsNear(lat: 9.9356, lon: -84.049, radiusKm: 0.5, page: 1, pageSize: 5) {
    edges {
      stopName
      stopLat
      stopLon
    }
    pageInfo {
      totalCount
    }
  }
}

Nested Query:

query {
  route(id: 1) {
    routeShortName
    routeLongName
    agency {
      agencyName
    }
    trips {
      tripHeadsign
      stops {
        stopName
        stopLat
        stopLon
      }
    }
  }
}

Integration Testing

Python:

import requests

query = """
query {
  stops(page: 1, pageSize: 5) {
    edges { stopName stopLat stopLon }
    pageInfo { totalCount }
  }
}
"""

response = requests.post(
    "http://localhost:8000/gql/",
    json={"query": query},
    headers={"Content-Type": "application/json"}
)
print(response.json())

References

• Related Issue: GraphQL API integration feature
• Dependencies: Strawberry GraphQL 0.285.0, Strawberry Django

Commits in This Branch

1. 78c9634 - docs(gql): add CHANGELOG and update README with GraphQL API documentation
2. 7726886 - fix(gql): rename graphql app to gql to avoid naming conflict
3. 6a4bef8 - docs(gql): add comprehensive documentation and demo queries
4. 5b920ae - refactor(gql): rename gql_schema to graphql and convert to Django app
5. 96ad2c1 - chore(gql): update uv.lock with Strawberry GraphQL dependencies
6. 3e5f6fd - feat(gql): complete GraphQL schema with GTFS core models and pagination
7. 145f7d1 - feat(gql): add GraphQL support with Strawberry Django integration

Checklist

• All tests passing (gql test suite: 219 lines)
• Documentation complete (README, CHANGELOG, gql/README.md, gql/DEMO_QUERIES.md)
• CHANGELOG.md updated following Keep a Changelog format
• README.md updated with GraphQL API section
• GraphiQL interface tested and working
• Query resolvers optimized with ORM best practices
• Pagination implemented using Connection pattern
• Geographic search validated with PostGIS
• Demo queries tested and documented
• Integration examples provided (Python, JavaScript, cURL)
• Code follows project conventions (Conventional Commits)
• No breaking changes to existing APIs
• Ready for review and merge

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Reviewers: Please Verify

1. GraphiQL Interface: Access http://localhost:8000/gql/ and verify interactive interface works
2. Test Suite: Run python manage.py test gql - all tests should pass
3. Documentation: Review gql/README.md for completeness and accuracy
4. Query Examples: Test demo queries from gql/DEMO_QUERIES.md in GraphiQL
5. Geographic Search: Verify stopsNear query with sample coordinates
6. Nested Queries: Test multi-level nested queries (route → trips → stops)
7. Pagination: Verify pagination works correctly with page and pageSize parameters
8. CHANGELOG: Confirm CHANGELOG.md follows Keep a Changelog format
9. README: Verify README.md GraphQL section is clear and helpful
10. No Regressions: Confirm existing REST API endpoints still work

Future Enhancements

• Mutations for data modification (currently read-only)
• Real-time subscriptions for live data updates
• Authentication and authorization integration
• Query complexity limits and depth restrictions
• DataLoader integration for batch loading optimization
• Rate limiting specific to GraphQL endpoint
• Metrics and monitoring for GraphQL queries

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Ready for Production: ✅ Yes
Backward Compatible: ✅ Yes
Breaking Changes: ❌ None
Documentation Complete: ✅ Yes