FitTrack_GarminSync/specs/010-specification-overview-the/research.md

Research: Persist Garmin Authentication for Stateless Sync

Date: 2025-12-22

This document outlines the decisions made regarding the technical implementation for persisting Garmin authentication sessions.

1. Authentication Library

• Decision: Use the garth library for handling Garmin Connect authentication.
• Rationale: The initial feature description explicitly mentions garth. This library is purpose-built for interacting with the Garmin Connect API, handles MFA, and most importantly, supports session export (dumps) and import (loads). This is the cornerstone of the "stateless sync" requirement, allowing us to persist the session state. It aligns with the existing project dependencies mentioned in GEMINI.md.
• Alternatives considered:
  • garminconnect: Another popular library. While it's great for fetching data, its session management is not as explicitly designed for serialization and deserialization as garth's, which is critical for this feature. We will continue to use it for data fetching, but garth will manage the authentication lifecycle.

2. Session Data Storage

• Decision: Store the serialized garth session in the CentralDB.
• Rationale: The feature spec requires a persistent store. The CentralDB (as defined in the constitution and project context) is the designated single source of truth for user-related data. Storing the session here ensures that any service or background worker can access it. The session data will be stored as a text or blob type.
• Alternatives considered:
  • Redis Cache: Could be used for faster access, but it's not guaranteed to be persistent. The constitution mentions Redis for rate limiting, not for primary data storage.
  • Local File System: Not suitable for a distributed or stateless service architecture, as different workers would not have access to the same session file.

3. API Framework

• Decision: Use FastAPI for the new API endpoints.
• Rationale: The project constitution mandates FastAPI for all API services. It's already in use in the project, ensuring consistency. Pydantic, which comes with FastAPI, will be used for request/response modeling.
• Alternatives considered: None, as this is a strict requirement from the project constitution.

4. Database Interaction

• Decision: Use SQLAlchemy to interact with the CentralDB.
• Rationale: The constitution specifies SQLAlchemy as the ORM. This ensures that the data model for the GarminAuthenticationState is managed consistently with other project models.
• Alternatives considered: None. This is a constitutional requirement.

Conclusion

The technical approach is a straightforward integration of garth's session management with the existing FastAPI and SQLAlchemy stack. All technical choices are dictated by the feature's core requirements and the project's established constitution.