feat: let admins manage model placement

packages/node/meshnet_node/torch_server.py

@@ -1545,6 +1545,26 @@ class TorchNodeServer:
 
     def apply_tracker_directives(self, directives: list[dict]) -> dict | None:
         """Apply tracker shard directives (LOAD_SHARD replace, ADD_SHARD load-more)."""
+        drop_directive = next(
+            (directive for directive in reversed(directives) if directive.get("action") == "DROP_SHARD"),
+            None,
+        )
+        if drop_directive is not None:
+            model_id = str(drop_directive.get("model") or "")
+            removed = self._backends.pop(model_id, None)
+            if removed is None:
+                return None
+            if self._backends:
+                self._backend = next(iter(self._backends.values()))
+                self._tracker_mode = self._backend.shard_start == 0
+            else:
+                self._backend = None
+                self._tracker_mode = False
+            if self._server is not None:
+                self._server.backends = dict(self._backends)
+                self._server.backend = self._backend
+                self._server.tracker_mode = self._tracker_mode
+            return {"action": "DROP_SHARD", "model": model_id}
         add_directive = next(
             (directive for directive in reversed(directives) if directive.get("action") == "ADD_SHARD"),
             None,
@@ -1574,6 +1594,8 @@ class TorchNodeServer:
             flush=True,
         )
         try:
+            if replacing:
+                self._backends.clear()
             new_backend = _load_backend(model_id, shard_start, shard_end, quantization, self._cache_dir)
         except TypeError:
             new_backend = _load_backend(model_id, shard_start, shard_end, quantization)