Call TriggerResubscribeIfScheduled on mDNS re-discovery

If we have active subscriptions, and we re-discover the device through
mDNS, we can ask the SDK to re-subscribe to the device immediately.
This should make device to be available quicker when they come back
online.

matter_server/server/device_controller.py

@@ -1301,6 +1301,15 @@ def _on_mdns_operational_node_state(
         elif (now - last_seen) > NODE_MDNS_BACKOFF:
             # node came back online after being offline for a while or restarted
             logger.info("Node %s re-discovered on MDNS", node_id)
+        elif state_change == ServiceStateChange.Added:
+            # Trigger node re-subscriptions when mDNS entry got added
+            logger.info("Node %s activity on MDNS, trigger resubscribe", node_id)
+            asyncio.create_task(
+                self._chip_device_controller.trigger_resubscribe_if_scheduled(
+                    node_id, "mDNS state change detected"
+                )
+            )
+            return
         else:
             # ignore all other cases
             return

matter_server/server/sdk.py

@@ -396,3 +396,14 @@ async def shutdown_subscription(self, node_id: int) -> None:
     def node_has_subscription(self, node_id: int) -> bool:
         """Check if a node has an active subscription."""
         return node_id in self._subscriptions
+
+    async def trigger_resubscribe_if_scheduled(self, node_id: int, reason: str) -> None:
+        """Trigger resubscribe now if a resubscribe is scheduled.
+
+        If the ReadClient currently has a resubscription attempt scheduled, This
+        function allows to trigger that attempt immediately. This is useful
+        when the server side is up and communicating, and it's a good time to
+        try to resubscribe.
+        """
+        if sub := self._subscriptions.get(node_id, None):
+            await sub.TriggerResubscribeIfScheduled(reason)