Docker-Based Build System: Simplify WebRtcNet Setup & Save 71% on CI Costs

[General-Fault]

Overview

This is a product requirements document (PRD) for implementing a two-tier Docker-based build system that separates WebRTC compilation (expensive, infrequent) from WebRtcNet compilation (cheap, frequent).

Full PRD: See PRD-docker-build-system.md in the repository

Problem

• New contributor setup takes 2+ hours (Windows SDK, depot_tools, 10GB download)
• Each build takes 60-90 minutes (rebuilds WebRTC every time)
• No Codespaces support (requires full Windows machine)
• Expensive CI costs (~/year on GitHub Actions)

Solution

• WebRTC Builder Image: Builds once monthly, publishes to GHCR (~250 MB, .45/build)
• WebRtcNet Builder Image: Uses WebRTC as base, builds in 10-15 minutes (.05-0.10/build)
• Result: 71-76% cost savings + Codespaces support + 15-20 min build time for new contributors

Expected Outcomes

✅ Developer setup: 10 minutes (vs. 2+ hours)
✅ Local rebuild: 15 minutes (vs. 60+ minutes)
✅ CI costs: .45/month (vs. .00/month, 71% savings)
✅ Codespaces support: Now viable for full development
✅ New contributor friction: Dramatically reduced

Key Components

1. Dockerfile.webrtc - Multi-stage build for WebRTC artifacts
2. Dockerfile.webrtcnet - Lightweight build inheriting WebRTC base
3. GitHub Actions workflows - Smart change detection + conditional builds
4. Documentation - CONTRIBUTING.md with setup instructions for Docker, Local, Codespaces

Details

See PRD-docker-build-system.md for complete details including:

• 20 detailed user stories
• Implementation decisions with rationale
• Testing strategy
• Out-of-scope items
• Cost savings validation and success metrics