Cleaner discovery topics, ability to specify own node_id

config.yaml.example

@@ -9,6 +9,7 @@ mqtt:
 monitor:
   interval: 15               # seconds between stat publishes
   device_name: ""            # display name in HA; defaults to hostname
+  node_id: ""                # MQTT topic slug and unique_id prefix; defaults to hostname if empty
 
 sensors:
   cpu: true

monitor.py

@@ -62,6 +62,7 @@ def load_config(path: Path = CONFIG_PATH) -> dict:
     mn = cfg["monitor"]
     mn.setdefault("interval", 30)
     mn.setdefault("device_name", "")
+    mn.setdefault("node_id", "")
 
     s = cfg["sensors"]
     s.setdefault("cpu", True)
@@ -711,14 +712,14 @@ class DiscoveryPublisher:
     def __init__(
         self,
         client: mqtt.Client,
-        hostname: str,
+        node_id: str,
         device_name: str,
         state_topic: str,
         availability_topic: str,
         discovery_prefix: str = "homeassistant",
     ):
         self._client = client
-        self._hostname = hostname
+        self._node_id = node_id
         self._device_name = device_name
         self._state_topic = state_topic
         self._availability_topic = availability_topic
@@ -726,7 +727,7 @@ def __init__(
 
     def _device_block(self) -> dict:
         return {
-            "identifiers": [f"{self._hostname}_monitor"],
+            "identifiers": [f"{self._node_id}_monitor"],
             "name": self._device_name,
             "manufacturer": "monitor.py",
             "model": "Linux System Monitor",
@@ -740,7 +741,7 @@ def publish_all(self, sensor_defs: list[dict]) -> None:
 
     def _publish_one(self, defn: dict) -> None:
         key = defn["key"]
-        unique_id = f"{self._hostname}_{key}"
+        unique_id = f"{self._node_id}_{key}"
         object_id = unique_id
 
         payload: dict[str, Any] = {
@@ -762,7 +763,7 @@ def _publish_one(self, defn: dict) -> None:
             payload["icon"] = defn["icon"]
 
         discovery_topic = (
-            f"{self._discovery_prefix}/sensor/{object_id}/config"
+            f"{self._discovery_prefix}/sensor/{self._node_id}/{object_id}/config"
         )
         self._client.publish(
             discovery_topic,
@@ -836,22 +837,24 @@ def __init__(self, cfg: dict):
         self._cfg = cfg
         self._hostname = socket.gethostname()
         self._device_name = cfg["monitor"].get("device_name") or self._hostname
+        raw_node_id = cfg["monitor"].get("node_id", "").strip()
+        self._node_id = self._make_node_id(raw_node_id or self._hostname)
         self._interval = max(5, int(cfg["monitor"].get("interval", 30)))
 
         prefix = cfg["mqtt"]["topic_prefix"]
-        self._state_topic, self._avail_topic = make_topics(prefix, self._hostname)
+        self._state_topic, self._avail_topic = make_topics(prefix, self._node_id)
 
         self._collectors = self._build_collectors()
         self._sensor_defs = all_sensor_defs(self._collectors, self._hostname)
 
-        self._client = build_client(cfg, self._hostname)
+        self._client = build_client(cfg, self._node_id)
         self._client.on_connect = self._on_connect
         self._client.on_disconnect = self._on_disconnect
         self._client.on_message = self._on_message
 
         self._discovery = DiscoveryPublisher(
             self._client,
-            self._hostname,
+            self._node_id,
             self._device_name,
             self._state_topic,
             self._avail_topic,
@@ -862,6 +865,15 @@ def __init__(self, cfg: dict):
         # Warm up cpu_percent (first call always returns 0.0)
         psutil.cpu_percent(interval=None)
 
+    @staticmethod
+    def _make_node_id(name: str) -> str:
+        """Sanitize a string for use in MQTT topics and HA unique_ids."""
+        safe = "".join(c if c.isalnum() or c in "-_" else "-" for c in name.lower())
+        # Collapse consecutive hyphens and strip leading/trailing separators
+        while "--" in safe:
+            safe = safe.replace("--", "-")
+        return safe.strip("-_") or "monitor"
+
     def _build_collectors(self) -> list:
         s = self._cfg["sensors"]
         collectors = []