Merge pull request #135 from igorls/fix/chromadb-singleton

perf: cache ChromaDB PersistentClient instead of re-instantiating per call

mempalace/mcp_server.py

@@ -39,13 +39,21 @@ logger = logging.getLogger("mempalace_mcp")
 _config = MempalaceConfig()
 
 
+_client_cache = None
+_collection_cache = None
+
+
 def _get_collection(create=False):
-    """Return the ChromaDB collection, or None on failure."""
+    """Return the ChromaDB collection, caching the client between calls."""
+    global _client_cache, _collection_cache
     try:
-        client = chromadb.PersistentClient(path=_config.palace_path)
+        if _client_cache is None:
+            _client_cache = chromadb.PersistentClient(path=_config.palace_path)
         if create:
-            return client.get_or_create_collection(_config.collection_name)
-        return client.get_collection(_config.collection_name)
+            _collection_cache = _client_cache.get_or_create_collection(_config.collection_name)
+        elif _collection_cache is None:
+            _collection_cache = _client_cache.get_collection(_config.collection_name)
+        return _collection_cache
     except Exception:
         return None
 

tests/conftest.py

@@ -34,6 +34,24 @@ from mempalace.config import MempalaceConfig  # noqa: E402
 from mempalace.knowledge_graph import KnowledgeGraph  # noqa: E402
 
 
+@pytest.fixture(autouse=True)
+def _reset_mcp_cache():
+    """Reset the MCP server's cached ChromaDB client/collection between tests."""
+
+    def _clear_cache():
+        try:
+            from mempalace import mcp_server
+
+            mcp_server._client_cache = None
+            mcp_server._collection_cache = None
+        except (ImportError, AttributeError):
+            pass
+
+    _clear_cache()
+    yield
+    _clear_cache()
+
+
 @pytest.fixture(scope="session", autouse=True)
 def _isolate_home():
     """Ensure HOME points to a temp dir for the entire test session.

tests/test_mcp_server.py

@@ -151,9 +151,10 @@ class TestReadTools:
         assert result["taxonomy"]["project"]["frontend"] == 1
         assert result["taxonomy"]["notes"]["planning"] == 1
 
-    def test_no_palace_returns_error(self, monkeypatch, config, kg):
-        config._file_config["palace_path"] = "/nonexistent/path"
-        _patch_mcp_server(monkeypatch, config, "/nonexistent/path", kg)
+    def test_no_palace_returns_error(self, monkeypatch, config, kg, tmp_path):
+        missing = str(tmp_path / "missing")
+        config._file_config["palace_path"] = missing
+        _patch_mcp_server(monkeypatch, config, missing, kg)
         from mempalace.mcp_server import tool_status
 
         result = tool_status()

tests/test_searcher.py

@@ -30,8 +30,8 @@ class TestSearchMemories:
         result = search_memories("code", palace_path, n_results=2)
         assert len(result["results"]) <= 2
 
-    def test_no_palace_returns_error(self):
-        result = search_memories("anything", "/nonexistent/path")
+    def test_no_palace_returns_error(self, tmp_path):
+        result = search_memories("anything", str(tmp_path / "missing"))
         assert "error" in result
 
     def test_result_fields(self, palace_path, seeded_collection):