Adding shared chromaDB client option (#2886)

This pull request addresses the need to share a single `chromadb.Client`
instance across multiple instances of the `Chroma` class. By
implementing a shared client, we can maintain consistency and reduce
resource usage when multiple instances of the `Chroma` classes are
created. This is especially relevant in a web app, where having multiple
`Chroma` instances with a `persist_directory` leads to these clients not
being synced.

This PR implements this option while keeping the rest of the
architecture unchanged.

**Changes:**
1. Add a client attribute to the `Chroma` class to store the shared
`chromadb.Client` instance.
2. Modify the `from_documents` method to accept an optional client
parameter.
3. Update the `from_documents` method to use the shared client if
provided or create a new client if not provided.

Let me know if anything needs to be modified - thanks again for your
work on this incredible repo

langchain/vectorstores/chroma.py

@@ -60,6 +60,7 @@ class Chroma(VectorStore):
         persist_directory: Optional[str] = None,
         client_settings: Optional[chromadb.config.Settings] = None,
         collection_metadata: Optional[Dict] = None,
+        client: Optional[chromadb.Client] = None,
     ) -> None:
         """Initialize with Chroma client."""
         try:
@@ -71,15 +72,20 @@ class Chroma(VectorStore):
                 "Please install it with `pip install chromadb`."
             )
 
-        if client_settings:
-            self._client_settings = client_settings
+        if client is not None:
+            self._client = client
         else:
-            self._client_settings = chromadb.config.Settings()
-            if persist_directory is not None:
-                self._client_settings = chromadb.config.Settings(
-                    chroma_db_impl="duckdb+parquet", persist_directory=persist_directory
-                )
-        self._client = chromadb.Client(self._client_settings)
+            if client_settings:
+                self._client_settings = client_settings
+            else:
+                self._client_settings = chromadb.config.Settings()
+                if persist_directory is not None:
+                    self._client_settings = chromadb.config.Settings(
+                        chroma_db_impl="duckdb+parquet",
+                        persist_directory=persist_directory,
+                    )
+            self._client = chromadb.Client(self._client_settings)
+
         self._embedding_function = embedding_function
         self._persist_directory = persist_directory
         self._collection = self._client.get_or_create_collection(
@@ -279,6 +285,7 @@ class Chroma(VectorStore):
         collection_name: str = _LANGCHAIN_DEFAULT_COLLECTION_NAME,
         persist_directory: Optional[str] = None,
         client_settings: Optional[chromadb.config.Settings] = None,
+        client: Optional[chromadb.Client] = None,
         **kwargs: Any,
     ) -> Chroma:
         """Create a Chroma vectorstore from a raw documents.
@@ -303,6 +310,7 @@ class Chroma(VectorStore):
             embedding_function=embedding,
             persist_directory=persist_directory,
             client_settings=client_settings,
+            client=client,
         )
         chroma_collection.add_texts(texts=texts, metadatas=metadatas, ids=ids)
         return chroma_collection
@@ -316,6 +324,7 @@ class Chroma(VectorStore):
         collection_name: str = _LANGCHAIN_DEFAULT_COLLECTION_NAME,
         persist_directory: Optional[str] = None,
         client_settings: Optional[chromadb.config.Settings] = None,
+        client: Optional[chromadb.Client] = None,  # Add this line
         **kwargs: Any,
     ) -> Chroma:
         """Create a Chroma vectorstore from a list of documents.
@@ -343,4 +352,5 @@ class Chroma(VectorStore):
             collection_name=collection_name,
             persist_directory=persist_directory,
             client_settings=client_settings,
+            client=client,
         )