Update embedding_model.py (#9083)

### What problem does this PR solve?

Reduce the logic scope for DefaultEmbedding

### Type of change

- [x] Refactoring

rag/llm/embedding_model.py

@@ -60,7 +60,6 @@ class Base(ABC):
 
 class DefaultEmbedding(Base):
     _FACTORY_NAME = "BAAI"
-    os.environ["CUDA_VISIBLE_DEVICES"] = "0"
     _model = None
     _model_name = ""
     _model_lock = threading.Lock()
@@ -78,9 +77,13 @@ class DefaultEmbedding(Base):
 
         """
         if not settings.LIGHTEN:
+            input_cuda_visible_devices = None
             with DefaultEmbedding._model_lock:
                 import torch
                 from FlagEmbedding import FlagModel
+                if "CUDA_VISIBLE_DEVICES" in os.environ:
+                    input_cuda_visible_devices = os.environ["CUDA_VISIBLE_DEVICES"]
+                    os.environ["CUDA_VISIBLE_DEVICES"] = "0" # handle some issues with multiple GPUs when initializing the model
 
                 if not DefaultEmbedding._model or model_name != DefaultEmbedding._model_name:
                     try:
@@ -95,6 +98,10 @@ class DefaultEmbedding(Base):
                             repo_id="BAAI/bge-large-zh-v1.5", local_dir=os.path.join(get_home_cache_dir(), re.sub(r"^[a-zA-Z0-9]+/", "", model_name)), local_dir_use_symlinks=False
                         )
                         DefaultEmbedding._model = FlagModel(model_dir, query_instruction_for_retrieval="为这个句子生成表示以用于检索相关文章：", use_fp16=torch.cuda.is_available())
+                    finally:
+                        if input_cuda_visible_devices:
+                            # restore CUDA_VISIBLE_DEVICES
+                            os.environ["CUDA_VISIBLE_DEVICES"] = input_cuda_visible_devices
         self._model = DefaultEmbedding._model
         self._model_name = DefaultEmbedding._model_name