Daemon Package

@habit-tracker/daemon

Background service that enforces website blocking by managing /etc/hosts. Runs with elevated privileges and communicates with the backend via Unix socket IPC.

Key Files

File	Purpose
src/index.ts	Main daemon loop and lifecycle management
src/hosts-manager.ts	/etc/hosts file manipulation with backup/restore
src/scheduler.ts	Habit checking logic and deadline calculations
src/socket-server.ts	Unix socket IPC server for backend communication
src/schema.ts	Drizzle ORM database schema definitions

How Blocking Works

1. Trigger: Deadline passes OR backend signals state change
2. Check: Daemon queries backend API for incomplete timed habits
3. Block: If any habits are overdue, add domains to /etc/hosts
4. Unblock: When all overdue habits are completed/skipped, remove entries

The daemon modifies /etc/hosts with entries like:

# HABIT-TRACKER-START
127.0.0.1 twitter.com
127.0.0.1 www.twitter.com
127.0.0.1 reddit.com
127.0.0.1 www.reddit.com
# HABIT-TRACKER-END

Development

# Run daemon (requires sudo for /etc/hosts access)
sudo npm run dev -w @habit-tracker/daemon

# Check daemon status
npm run daemon:status

# Emergency restore (remove all blocks)
npm run daemon:restore

# View logs
tail -f ~/.habit-tracker/logs/daemon.log

Architecture

The daemon uses three mechanisms to stay in sync:

1. IPC Socket: Backend notifies daemon immediately on habit completion
2. Deadline Timers: Precise timers fire when habit deadlines pass
3. Fallback Polling: 60-second interval catch-all for edge cases

Data Flow

Backend API → (habit completed) → IPC trigger → checkAndUpdate()
                                               ↓
Deadline Timer → (time passes) ────────────────→ checkHabits()
                                               ↓
                                         updateHostsFile()
                                               ↓
                                         /etc/hosts modified

IPC Commands

The daemon listens on a Unix socket for commands from the backend:

Command	Description
ping	Check if daemon is running (returns pong)
refresh	Re-check habits and update blocking state
reset	Emergency reset - unblock all websites

Safety Features

• Backup/Restore: Original /etc/hosts backed up before modification
• Marker Comments: Only modifies lines between HABIT-TRACKER-START/END
• Graceful Shutdown: Cleans up on SIGINT/SIGTERM
• Error Logging: All operations logged to ~/.habit-tracker/logs/