"""MQTT client integration (paho-mqtt 2.x). Provides :class:`MqttManager`: a long-lived MQTT client that runs paho's loop in a background thread. Designed to be started in FastAPI's lifespan and shared across the application as a module-level singleton (``mqtt_manager``). Key design decisions -------------------- - **paho 2.x API**: ``Client`` requires ``CallbackAPIVersion.VERSION2`` as the first positional argument. VERSION2 on_connect callback receives ``(client, userdata, connect_flags, reason_code, properties)`` — not the older RC int. - **Background thread**: ``loop_start()`` spawns a daemon thread; ``loop_stop()`` joins it cleanly on shutdown. - **Never crash the process**: all paho operations are wrapped in try/except; connection failure is logged but does not propagate to the caller. - **Password safety**: the MQTT password is never passed to ``logger`` calls. - **Reconnect**: ``reconnect(settings)`` tears down the old client and establishes a fresh connection with the new settings. Callers (e.g. PUT /api/config) call this after saving MQTT-related config values. - **Subscribe**: ``subscribe(topic, handler)`` registers a topic → handler mapping. Subscriptions are re-established automatically on reconnect. The ``on_message`` callback dispatches incoming payloads to the registered handler; handler exceptions are caught and logged so they never crash the paho loop thread or the network connection. """ from __future__ import annotations import logging import threading from collections.abc import Callable from typing import TYPE_CHECKING import paho.mqtt.client as mqtt if TYPE_CHECKING: from app.config import Settings logger = logging.getLogger(__name__) # MQTT settings keys that, when changed, should trigger a reconnect. MQTT_SETTINGS_KEYS = { "mqtt_enabled", "mqtt_broker_host", "mqtt_broker_port", "mqtt_username", "mqtt_password", "mqtt_tls_enabled", } def _is_configured(settings: Settings) -> bool: """Return True if MQTT is enabled *and* the broker host is set.""" return bool(settings.mqtt_enabled and settings.mqtt_broker_host) class MqttManager: """Long-lived MQTT client wrapper. Lifecycle --------- 1. ``connect(settings)`` — start background loop + connect to broker. 2. ``publish(...)`` — publish messages while connected. 3. ``disconnect()`` — graceful teardown (called on app shutdown). 4. ``reconnect(settings)`` — disconnect then re-connect with new settings (called after saving updated MQTT configuration). When MQTT is not enabled or not configured, all methods are no-ops. Connection failures are caught and logged; they do not raise. """ def __init__(self) -> None: self._client: mqtt.Client | None = None self._lock = threading.Lock() self._connected = False # topic → handler registry; persists across reconnects so subscriptions # are automatically re-established when the client reconnects. self._subscriptions: dict[str, Callable[[bytes], None]] = {} # ------------------------------------------------------------------ # Public properties # ------------------------------------------------------------------ @property def is_connected(self) -> bool: """True if the underlying paho client is currently connected.""" return self._connected # ------------------------------------------------------------------ # Public interface # ------------------------------------------------------------------ def is_configured(self, settings: Settings) -> bool: """Return True if MQTT is enabled and broker host is configured.""" return _is_configured(settings) def connect(self, settings: Settings) -> None: """Connect to the MQTT broker and start the background loop thread. No-op if MQTT is not enabled or broker host is not set. Connection errors are logged but do not raise. """ if not _is_configured(settings): logger.debug("MQTT not configured or not enabled — skipping connect.") return with self._lock: self._start_client(settings) def disconnect(self) -> None: """Disconnect from the broker and stop the background loop thread. No-op if no client is active. """ with self._lock: self._stop_client() def reconnect(self, settings: Settings) -> None: """Disconnect the current client (if any) and reconnect with *settings*. Call this after saving updated MQTT configuration values. No-op if MQTT is not enabled or broker host is not set. """ with self._lock: self._stop_client() self.connect(settings) def publish( self, topic: str, payload: str | bytes | None, *, retain: bool = False, qos: int = 0, ) -> None: """Publish a message to *topic*. If the client is not connected the call is silently skipped. Errors are logged but do not raise. """ with self._lock: client = self._client if client is None or not self._connected: logger.debug("MQTT publish skipped — not connected (topic=%s).", topic) return try: client.publish(topic, payload=payload, qos=qos, retain=retain) except Exception: logger.exception("MQTT publish error (topic=%s).", topic) def subscribe(self, topic: str, handler: Callable[[bytes], None]) -> None: """Register *handler* to be called when a message arrives on *topic*. If the client is already connected, the subscription is sent to the broker immediately. Otherwise it is queued and will be established the next time ``_on_connect`` fires (including after a reconnect). Handler exceptions are swallowed by the ``on_message`` dispatcher so that a buggy handler can never crash the paho loop thread. """ self._subscriptions[topic] = handler # Grab the client reference outside the lock to avoid holding the lock # while calling back into paho (which may itself acquire internal locks). with self._lock: client = self._client connected = self._connected if client is not None and connected: try: client.subscribe(topic) logger.debug("MQTT subscribed to topic=%s (immediate).", topic) except Exception: logger.exception("MQTT subscribe error (topic=%s).", topic) # ------------------------------------------------------------------ # Internal helpers — must be called with self._lock held # ------------------------------------------------------------------ def _start_client(self, settings: Settings) -> None: """Build a fresh paho Client, configure it, and call loop_start + connect.""" client = mqtt.Client( callback_api_version=mqtt.CallbackAPIVersion.VERSION2, client_id="home-automation", ) # Callbacks — VERSION2 on_connect signature: # (client, userdata, connect_flags, reason_code, properties) def _on_connect( _client: mqtt.Client, _userdata: object, _flags: mqtt.ConnectFlags, reason_code: mqtt.ReasonCode, _properties: mqtt.Properties | None, ) -> None: if reason_code.is_failure: logger.warning("MQTT connection refused: %s", reason_code) self._connected = False else: logger.info("MQTT connected (reason_code=%s).", reason_code) self._connected = True # Re-establish all registered subscriptions after (re-)connect. for sub_topic in self._subscriptions: try: _client.subscribe(sub_topic) logger.debug("MQTT re-subscribed to topic=%s.", sub_topic) except Exception: logger.exception( "MQTT re-subscribe failed (topic=%s).", sub_topic ) # VERSION2 on_disconnect signature: # (client, userdata, disconnect_flags, reason_code, properties) def _on_disconnect( _client: mqtt.Client, _userdata: object, _disconnect_flags: mqtt.DisconnectFlags, reason_code: mqtt.ReasonCode, _properties: mqtt.Properties | None, ) -> None: self._connected = False if reason_code.is_failure: logger.warning("MQTT disconnected unexpectedly (reason_code=%s).", reason_code) else: logger.info("MQTT disconnected cleanly.") # VERSION2 on_message signature: (client, userdata, message) def _on_message( _client: mqtt.Client, _userdata: object, message: mqtt.MQTTMessage, ) -> None: handler = self._subscriptions.get(message.topic) if handler is None: logger.debug( "MQTT on_message: no handler for topic=%s.", message.topic ) return try: handler(message.payload) except Exception: logger.exception( "MQTT message handler raised for topic=%s (swallowed).", message.topic, ) client.on_connect = _on_connect client.on_disconnect = _on_disconnect client.on_message = _on_message # TLS if settings.mqtt_tls_enabled: try: client.tls_set() except Exception: logger.exception("MQTT TLS setup failed.") return # Credentials — never log the password if settings.mqtt_username: client.username_pw_set( username=settings.mqtt_username, password=settings.mqtt_password or None, ) # Start background loop thread *before* connect so paho can handle # the connection handshake asynchronously. client.loop_start() try: client.connect( host=settings.mqtt_broker_host, port=settings.mqtt_broker_port, keepalive=60, ) except Exception: # Log without leaking the password logger.exception( "MQTT connect failed (host=%s, port=%s). Stopping loop.", settings.mqtt_broker_host, settings.mqtt_broker_port, ) try: client.loop_stop() except Exception: pass return self._client = client logger.info( "MQTT client started (host=%s, port=%s).", settings.mqtt_broker_host, settings.mqtt_broker_port, ) def _stop_client(self) -> None: """Disconnect and stop the background loop. Idempotent.""" client = self._client if client is None: return self._client = None self._connected = False try: client.disconnect() except Exception: logger.debug("MQTT disconnect raised (ignoring).", exc_info=True) try: client.loop_stop() except Exception: logger.debug("MQTT loop_stop raised (ignoring).", exc_info=True) logger.info("MQTT client stopped.") # --------------------------------------------------------------------------- # Module-level singleton — shared across lifespan and route handlers # --------------------------------------------------------------------------- mqtt_manager = MqttManager()