ENH: (Issue #1234) add exception when user tries to create more than one persistent or ephemeral client.

chromadb/__init__.py

@@ -18,6 +18,8 @@
     WhereDocument,
     UpdateCollectionMetadata,
 )
+from chromadb.utils import once
+
 
 # Re-export types from chromadb.types
 __all__ = [
@@ -94,7 +96,7 @@ def configure(**kwargs) -> None:  # type: ignore
 def get_settings() -> Settings:
     return __settings
 
-
+@once
 def EphemeralClient(settings: Settings = Settings()) -> API:
     """
     Creates an in-memory instance of Chroma. This is useful for testing and
@@ -104,7 +106,7 @@ def EphemeralClient(settings: Settings = Settings()) -> API:
 
     return Client(settings)
 
-
+@once
 def PersistentClient(path: str = "./chroma", settings: Settings = Settings()) -> API:
     """
     Creates a persistent instance of Chroma that saves to disk. This is useful for

chromadb/test/test_client.py

@@ -3,6 +3,7 @@
 import chromadb.server.fastapi
 import pytest
 import tempfile
+import gc
 
 
 @pytest.fixture
@@ -35,3 +36,33 @@ def test_persistent_client(persistent_api: API) -> None:
 def test_http_client(http_api: API) -> None:
     settings = http_api.get_settings()
     assert settings.chroma_api_impl == "chromadb.api.fastapi.FastAPI"
+
+def test_multiple_persistent_client() -> None:
+    with pytest.raises(RuntimeError):
+        a = chromadb.PersistentClient(
+            path=tempfile.gettempdir() + "/test_server",
+        )
+        b = chromadb.PersistentClient(
+            path=tempfile.gettempdir() + "/test_server",
+        )
+
+def test_multiple_ephemeral_client() -> None:
+    with pytest.raises(RuntimeError):
+        a = chromadb.EphemeralClient()
+        b = chromadb.EphemeralClient()
+
+def test_gc_ephemeral_client() -> None:
+    # need to manually gargabe collect otherwise tests fail from above instantiations.
+    gc.collect()
+    a = chromadb.EphemeralClient()
+    del a
+    gc.collect()
+    b = chromadb.EphemeralClient()
+
+def test_gc_persistent_client() -> None:
+    # need to manually gargabe collect otherwise tests fail from above instantiations.
+    gc.collect()
+    a = chromadb.PersistentClient(path=tempfile.gettempdir() + "/test_server",)
+    del a
+    gc.collect()
+    b = chromadb.PersistentClient(path=tempfile.gettempdir() + "/test_server",)

chromadb/utils/__init__.py

@@ -1,4 +1,5 @@
 import importlib
+import weakref
 from typing import Type, TypeVar, cast
 
 C = TypeVar("C")
@@ -10,3 +11,22 @@ def get_class(fqn: str, type: Type[C]) -> Type[C]:
     module = importlib.import_module(module_name)
     cls = getattr(module, class_name)
     return cast(Type[C], cls)
+
+def once(func):
+    """ 
+    Decorator that limits a function to one call. 
+    """
+    instance_ref = None
+    def wrapper(*args, **kwargs):
+        nonlocal instance_ref
+        # if first run or the object created has been garbage collected. 
+        if instance_ref is None or instance_ref() is None:
+            instance = func(*args, **kwargs)
+            instance_ref = weakref.ref(instance) 
+            return instance
+        else:
+            raise RuntimeError(f"Function {func.__name__} has already been called. \
+            You should try and use only one instance of the Client.")
+            return None
+
+    return wrapper