Harrison/opensearch vectorstore (#1907)

Co-authored-by: Mehmet Öner Yalçın <oneryalcin@gmail.com>

langchain/vectorstores/opensearch_vector_search.py

@@ -363,7 +363,11 @@ class OpenSearchVectorSearch(VectorStore):
         embeddings = embedding.embed_documents(texts)
         _validate_embeddings_and_bulk_size(len(embeddings), bulk_size)
         dim = len(embeddings[0])
-        index_name = uuid.uuid4().hex
+        # Get the index name from either from kwargs or ENV Variable
+        # before falling back to random generation
+        index_name = get_from_dict_or_env(
+            kwargs, "index_name", "OPENSEARCH_INDEX_NAME", default=uuid.uuid4().hex
+        )
         is_appx_search = _get_kwargs_value(kwargs, "is_appx_search", True)
         if is_appx_search:
             engine = _get_kwargs_value(kwargs, "engine", "nmslib")