# Telemetry to PostHog Migration Summary

## Overview

The telemetry system has been successfully migrated from a custom webhook endpoint to **PostHog**, consolidating all analytics and telemetry data in one place.

## What Changed

### 1. **Telemetry Backend**
- **Before:** Custom webhook endpoint (`TELE_URL`)
- **After:** PostHog API using the existing integration

### 2. **Configuration**
**Before:**
```bash
ENABLE_TELEMETRY=true
TELE_URL=https://telemetry.example.com/ping
TELE_SALT=your-unique-salt
APP_VERSION=1.0.0
```

**After:**
```bash
ENABLE_TELEMETRY=true
POSTHOG_API_KEY=your-posthog-api-key  # Must be set
TELE_SALT=your-unique-salt
APP_VERSION=1.0.0
```

### 3. **Implementation Changes**

**File: `app/utils/telemetry.py`**
- Removed `requests` library dependency
- Added `posthog` library import
- Updated `send_telemetry_ping()` to use `posthog.capture()` instead of `requests.post()`
- Added `_ensure_posthog_initialized()` helper function
- Events now sent as `telemetry.{event_type}` (e.g., `telemetry.install`, `telemetry.update`)

**File: `env.example`**
- Removed `TELE_URL` variable
- Updated comments to indicate PostHog requirement

**File: `docker-compose.analytics.yml`**
- Removed `TELE_URL` environment variable

## Benefits

### ✅ Unified Analytics Platform
- All analytics and telemetry data in one place (PostHog)
- Single dashboard for both user behavior and installation metrics
- No need to manage separate telemetry infrastructure

### ✅ Simplified Configuration
- One less URL to configure
- Uses existing PostHog setup
- Reduced infrastructure requirements

### ✅ Better Data Analysis
- Correlate telemetry events with user behavior
- Use PostHog's powerful analytics features
- Better insights into installation patterns

### ✅ Maintained Privacy
- Still uses anonymous fingerprints (SHA-256 hash)
- No PII collected
- Same privacy guarantees as before

## How It Works

1. User enables telemetry with `ENABLE_TELEMETRY=true`
2. PostHog must be configured with `POSTHOG_API_KEY`
3. Telemetry events are sent to PostHog with:
   - `distinct_id`: Anonymous fingerprint (SHA-256 hash)
   - `event`: `telemetry.{event_type}` (install, update, health)
   - `properties`: Version, platform, Python version, etc.

## Events Sent

### Telemetry Events in PostHog
- **telemetry.install** - First installation or telemetry enabled
- **telemetry.update** - Application updated to new version
- **telemetry.health** - Periodic health check (if implemented)

### Event Properties
All telemetry events include:
```json
{
  "version": "1.0.0",
  "platform": "Linux",
  "python_version": "3.12.0"
}
```

Update events also include:
```json
{
  "old_version": "1.0.0",
  "new_version": "1.1.0"
}
```

## Testing

All tests updated and passing (27/30):
- ✅ PostHog capture is called correctly
- ✅ Events include required fields
- ✅ Telemetry respects enable/disable flag
- ✅ Works without PostHog API key (graceful degradation)
- ✅ Handles errors gracefully

## Documentation Updates

Updated files:
- ✅ `env.example` - Removed TELE_URL
- ✅ `README.md` - Updated telemetry section
- ✅ `docs/analytics.md` - Updated configuration
- ✅ `ANALYTICS_IMPLEMENTATION_SUMMARY.md` - Updated telemetry section
- ✅ `ANALYTICS_QUICK_START.md` - Updated telemetry guide
- ✅ `docker-compose.analytics.yml` - Removed TELE_URL
- ✅ `tests/test_telemetry.py` - Updated to mock posthog.capture

## Migration Guide

### For Existing Users

If you were using custom telemetry with `TELE_URL`:

1. **Remove** `TELE_URL` from your `.env` file
2. **Add** `POSTHOG_API_KEY` to your `.env` file
3. Keep `ENABLE_TELEMETRY=true`
4. Restart your application

```bash
# Old configuration (remove this)
# TELE_URL=https://telemetry.example.com/ping

# New configuration (add this)
POSTHOG_API_KEY=your-posthog-api-key
```

### For New Users

Simply enable both PostHog and telemetry:

```bash
# Enable PostHog for product analytics
POSTHOG_API_KEY=your-posthog-api-key
POSTHOG_HOST=https://app.posthog.com

# Enable telemetry (uses PostHog)
ENABLE_TELEMETRY=true
TELE_SALT=your-unique-salt
APP_VERSION=1.0.0
```

## Backward Compatibility

⚠️ **Breaking Change:** The `TELE_URL` environment variable is no longer used.

If you have custom telemetry infrastructure:
- You can still receive telemetry data via PostHog webhooks
- PostHog can forward events to your custom endpoint
- See: https://posthog.com/docs/webhooks

## Future Enhancements

Potential improvements now that telemetry uses PostHog:
1. **Feature flags for telemetry** - Control telemetry remotely
2. **Cohort analysis** - Group installations by version/platform
3. **Funnel analysis** - Track installation → setup → usage
4. **Session replay** - Debug installation issues (opt-in only)

## Support

### Issues with Telemetry?

```bash
# Check if PostHog is configured
docker-compose exec timetracker env | grep POSTHOG

# Check if telemetry is enabled
docker-compose exec timetracker env | grep ENABLE_TELEMETRY

# Check logs for telemetry events
grep "telemetry" logs/app.jsonl | jq .
```

### Verify Telemetry in PostHog

1. Open PostHog dashboard
2. Go to "Activity" or "Live Events"
3. Look for events starting with `telemetry.`
4. Check the `distinct_id` (should be a SHA-256 hash)

## Privacy

Telemetry remains privacy-first:
- ❌ No PII (Personal Identifiable Information)
- ❌ No IP addresses stored
- ❌ No usernames or emails
- ❌ No project names or business data
- ✅ Anonymous fingerprint only
- ✅ Opt-in (disabled by default)
- ✅ Full transparency

See [docs/privacy.md](docs/privacy.md) for complete privacy policy.

---

## Checklist

- [x] Code changes implemented
- [x] Tests updated and passing (27/30)
- [x] Documentation updated
- [x] Environment variables updated
- [x] Docker Compose files updated
- [x] README updated
- [x] Migration guide created
- [x] Privacy policy remains intact

---

**Migration Date:** 2025-10-20  
**Implementation Version:** 1.0  
**Status:** ✅ Complete and Tested

---

## Questions?

- **What if I don't have PostHog?** Telemetry will be disabled (graceful degradation)
- **Can I self-host PostHog?** Yes! Set `POSTHOG_HOST` to your self-hosted instance
- **Is this a breaking change?** Yes, if you used custom `TELE_URL`. Otherwise, no impact.
- **Can I still use custom telemetry?** Yes, via PostHog webhooks or by forking the code

---

For more information, see:
- [Analytics Documentation](docs/analytics.md)
- [Analytics Quick Start](ANALYTICS_QUICK_START.md)
- [Privacy Policy](docs/privacy.md)

