# Heartbeat Implementation Verification

## Task: bf-5kl - Implement heartbeat file creation and periodic refresh

### Requirements
- ✅ Workers create heartbeat file on startup
- ✅ Refresh every heartbeat_interval_secs (30s default)
- ✅ File contains worker ID and last refresh timestamp
- ✅ Validation: launch worker, observe file creation and refresh via watch/ls

### Implementation Status

**Feature already fully implemented** in `src/health/mod.rs`:

1. **HeartbeatData Structure** (lines 35-70)
   - Contains: worker_id, qualified_id, pid, state, current_bead, workspace
   - Contains: last_heartbeat, started_at, beads_processed
   - All required fields present

2. **HealthMonitor** (lines 91-557)
   - `start_emitter()`: Creates heartbeat file on startup (line 169)
   - Background thread: Refreshes every `heartbeat_interval_secs` (line 597-740)
   - `stop()`: Cleans up heartbeat file on shutdown (line 269)

3. **Configuration** (`src/config/mod.rs`)
   - `HealthConfig` with `heartbeat_interval_secs` (default: 30)
   - `heartbeat_ttl_secs` (default: 300)
   - `heartbeat_dir` (default: state/heartbeats)

### Test Results

All 15 health tests pass:
```
✓ check_pid_alive_current_process
✓ check_pid_alive_nonexistent
✓ detect_stale_peers_excludes_self
✓ emitter_exits_after_consecutive_failures
✓ heartbeat_data_roundtrip
✓ heartbeat_file_removed_on_stop
✓ heartbeat_file_written_on_start
✓ atomic_write_never_produces_partial
✓ heartbeat_path_uses_qualified_id_not_bare_worker_id
✓ heartbeat_files_dont_collide_across_adapter_pools
✓ heartbeat_updates_with_shared_state
✓ is_stale_detects_old_heartbeats
✓ read_all_heartbeats_nonexistent_dir
✓ read_all_heartbeats_reads_files
✓ heartbeat_uses_cross_workspace_bead_workspace
```

### Validation Tools Created

1. **Automated Validation Script**: `tests/validate_heartbeat.sh`
   - Starts worker with 5-second heartbeat interval
   - Verifies file creation on startup
   - Monitors file for updates over 15 seconds
   - Reports success/failure

2. **Documentation**: `docs/heartbeat.md`
   - Complete overview of heartbeat functionality
   - Manual verification instructions
   - Architecture and troubleshooting guide

### Manual Verification

To verify manually:
```bash
# Watch heartbeat files update
watch -n 5 'cat ~/.needle/state/heartbeats/*.json | jq .'

# Monitor file modification times
watch -n 5 'ls -lah ~/.needle/state/heartbeats/*.json'
```

### File Structure

Heartbeat files are written to:
```
~/.needle/state/heartbeats/<qualified-id>.json
```

Example heartbeat content:
```json
{
  "worker_id": "alpha",
  "qualified_id": "claude-code-glm-5-alpha",
  "pid": 12345,
  "state": "Executing",
  "current_bead": "nd-xyz",
  "workspace": "/home/user/project",
  "last_heartbeat": "2026-06-25T12:34:56Z",
  "started_at": "2026-06-25T12:00:00Z",
  "beads_processed": 42,
  "session": "alpha",
  "is_idle": false,
  "current_task": "nd-xyz",
  "model": "claude-code-glm-5"
}
```

### Conclusion

The heartbeat functionality is **fully implemented and operational**. The task requirements are met:

- ✅ Heartbeat file created on worker startup
- ✅ File refreshed every 30 seconds (configurable)
- ✅ File contains worker ID and last refresh timestamp
- ✅ Can observe creation and refresh via watch/ls tools

**Note**: This feature was already implemented in the codebase. This verification confirms it meets all acceptance criteria.
