Fix: Enable Kuzu Concurrency

mem0/memory/kuzu_memory.py

@@ -1,4 +1,5 @@
 import logging
+from weakref import WeakValueDictionary
 
 from mem0.memory.utils import format_entities
 
@@ -27,6 +28,8 @@
 
 
 class MemoryGraph:
+    _db_objects: WeakValueDictionary[str, kuzu.Database] = WeakValueDictionary()
+
     def __init__(self, config):
         self.config = config
 
@@ -37,7 +40,14 @@ def __init__(self, config):
         )
         self.embedding_dims = self.embedding_model.config.embedding_dims
 
-        self.db = kuzu.Database(self.config.graph_store.config.db)
+        # Kuzu doesn't allow concurrent connections to the same Kuzu DB file from different `kuzu.Database` objects
+        # We must reuse the same `kuzu.Database` object to connect.
+        # See https://docs.kuzudb.com/concurrency.
+        kuzu_db_file = self.config.graph_store.config.db
+        if kuzu_db_file != ":memory:" and kuzu_db_file not in self._db_objects:
+            self.db = kuzu.Database(kuzu_db_file)
+            self._db_objects[kuzu_db_file] = self.db
+        self.db = self._db_objects[kuzu_db_file]
         self.graph = kuzu.Connection(self.db)
 
         self.node_label = ":Entity"