fix(router.py): give an 'info' log when fallbacks work successfully

litellm/router.py

@@ -1444,6 +1444,9 @@ class Router:
                             response = await self.async_function_with_retries(
                                 *args, **kwargs
                             )
+                            verbose_router_logger.info(
+                                "Successful fallback b/w models."
+                            )
                             return response
                         except Exception as e:
                             pass
@@ -1478,6 +1481,9 @@ class Router:
                             response = await self.async_function_with_fallbacks(
                                 *args, **kwargs
                             )
+                            verbose_router_logger.info(
+                                "Successful fallback b/w models."
+                            )
                             return response
                         except Exception as e:
                             raise e

litellm/tests/test_router_debug_logs.py

@@ -85,6 +85,7 @@ def test_async_fallbacks(caplog):
         "litellm.acompletion(model=gpt-3.5-turbo)\x1b[31m Exception OpenAIException - Error code: 401 - {'error': {'message': 'Incorrect API key provided: bad-key. You can find your API key at https://platform.openai.com/account/api-keys.', 'type': 'invalid_request_error', 'param': None, 'code': 'invalid_api_key'}} \nModel: gpt-3.5-turbo\nAPI Base: https://api.openai.com\nMessages: [{'content': 'Hello, how are you?', 'role': 'user'}]\nmodel_group: gpt-3.5-turbo\n\ndeployment: gpt-3.5-turbo\n\x1b[0m",
         "Falling back to model_group = azure/gpt-3.5-turbo",
         "litellm.acompletion(model=azure/chatgpt-v-2)\x1b[32m 200 OK\x1b[0m",
+        "Successful fallback b/w models.",
     ]
 
     # Assert that the captured logs match the expected log messages