fix(router.py): fix least-busy routing

litellm/__init__.py

@@ -9,6 +9,7 @@ input_callback: List[Union[str, Callable]] = []
 success_callback: List[Union[str, Callable]] = []
 failure_callback: List[Union[str, Callable]] = []
 callbacks: List[Callable] = []
+_async_input_callback: List[Callable] = [] # internal variable - async custom callbacks are routed here. 
 _async_success_callback: List[Callable] = [] # internal variable - async custom callbacks are routed here. 
 _async_failure_callback: List[Callable] = [] # internal variable - async custom callbacks are routed here. 
 pre_call_rules: List[Callable] = []

litellm/caching.py

@@ -61,8 +61,6 @@ class InMemoryCache(BaseCache):
                 cached_response = json.loads(original_cached_response)
             except: 
                 cached_response = original_cached_response
-            if isinstance(cached_response, dict): 
-                    cached_response['cache'] = True  # set cache-hit flag to True
             return cached_response
         return None
     
@@ -110,8 +108,6 @@ class RedisCache(BaseCache):
                     cached_response = json.loads(cached_response)  # Convert string to dictionary
                 except: 
                     cached_response = ast.literal_eval(cached_response)
-                if isinstance(cached_response, dict): 
-                    cached_response['cache'] = True  # set cache-hit flag to True
                 return cached_response
         except Exception as e:
             # NON blocking - notify users Redis is throwing an exception

litellm/integrations/custom_logger.py

@@ -28,6 +28,9 @@ class CustomLogger: # https://docs.litellm.ai/docs/observability/custom_callback
     def log_failure_event(self, kwargs, response_obj, start_time, end_time): 
         pass
     
+    async def async_log_pre_api_call(self, model, messages, kwargs):
+        pass
+
     async def async_log_success_event(self, kwargs, response_obj, start_time, end_time):
         pass
 
@@ -51,6 +54,22 @@ class CustomLogger: # https://docs.litellm.ai/docs/observability/custom_callback
             traceback.print_exc()
             print_verbose(f"Custom Logger Error - {traceback.format_exc()}")
 
+    async def async_log_input_event(self, model, messages, kwargs, print_verbose, callback_func):
+        try: 
+            kwargs["model"] = model
+            kwargs["messages"] = messages
+            kwargs["log_event_type"] = "pre_api_call"
+            await callback_func(
+                kwargs,
+            )
+            print_verbose(
+                f"Custom Logger - model call details: {kwargs}"
+            )
+        except: 
+            traceback.print_exc()
+            print_verbose(f"Custom Logger Error - {traceback.format_exc()}")
+    
+
     def log_event(self, kwargs, response_obj, start_time, end_time, print_verbose, callback_func):
         # Method definition
         try:

litellm/router.py

@@ -9,14 +9,14 @@
 
 from datetime import datetime
 from typing import Dict, List, Optional, Union, Literal, Any
-import random, threading, time, traceback
+import random, threading, time, traceback, uuid
 import litellm, openai
 from litellm.caching import RedisCache, InMemoryCache, DualCache
 import logging, asyncio
 import inspect, concurrent
 from openai import AsyncOpenAI
 from collections import defaultdict
-
+from litellm.router_strategy.least_busy import LeastBusyLoggingHandler
 class Router:
     """
     Example usage:
@@ -57,6 +57,7 @@ class Router:
     default_cache_time_seconds: int = 1 * 60 * 60  # 1 hour
     num_retries: int = 0
     tenacity = None
+    leastbusy_logger: Optional[LeastBusyLoggingHandler] = None
 
     def __init__(self,
                  model_list: Optional[list] = None,
@@ -107,10 +108,6 @@ class Router:
         self.default_litellm_params.setdefault("timeout", timeout)
         self.default_litellm_params.setdefault("max_retries", 0)
 
-
-        ### HEALTH CHECK THREAD ###
-        if self.routing_strategy == "least-busy":
-            self._start_health_check_thread()
         ### CACHING ###
         cache_type = "local" # default to an in-memory cache
         redis_cache = None
@@ -137,6 +134,16 @@ class Router:
             litellm.cache = litellm.Cache(type=cache_type, **cache_config)
             self.cache_responses = cache_responses
         self.cache = DualCache(redis_cache=redis_cache, in_memory_cache=InMemoryCache()) # use a dual cache (Redis+In-Memory) for tracking cooldowns, usage, etc.
+        ### ROUTING SETUP ### 
+        if routing_strategy == "least-busy":
+            self.leastbusy_logger = LeastBusyLoggingHandler(router_cache=self.cache) 
+            ## add callback
+            if isinstance(litellm.input_callback, list): 
+                litellm.input_callback.append(self.leastbusy_logger) # type: ignore
+            else: 
+                litellm.input_callback = [self.leastbusy_logger] # type: ignore
+            if isinstance(litellm.callbacks, list):
+                litellm.callbacks.append(self.leastbusy_logger) # type: ignore
         ## USAGE TRACKING ## 
         if isinstance(litellm.success_callback, list):
             litellm.success_callback.append(self.deployment_callback)
@@ -664,6 +671,7 @@ class Router:
             return kwargs
         except Exception as e: 
             raise e
+
     def _set_cooldown_deployments(self, 
                                   deployment: str):
         """
@@ -873,6 +881,10 @@ class Router:
         for model in self.model_list:
             litellm_params = model.get("litellm_params", {})
             model_name = litellm_params.get("model")
+            #### MODEL ID INIT ########
+            model_info = model.get("model_info", {})
+            model_info["id"] = model_info.get("id", str(uuid.uuid4()))
+            model["model_info"] = model_info
             ####  for OpenAI / Azure we need to initalize the Client for High Traffic ########
             custom_llm_provider = litellm_params.get("custom_llm_provider")
             if custom_llm_provider is None:
@@ -1119,8 +1131,8 @@ class Router:
         healthy_deployments = [m for m in self.model_list if m["model_name"] == model]
         if len(healthy_deployments) == 0: 
             # check if the user sent in a deployment name instead 
-
             healthy_deployments = [m for m in self.model_list if m["litellm_params"]["model"] == model]
+
         self.print_verbose(f"initial list of deployments: {healthy_deployments}")
         deployments_to_remove = [] 
         cooldown_deployments = self._get_cooldown_deployments()
@@ -1140,13 +1152,24 @@ class Router:
             model = litellm.model_alias_map[
                 model
             ]  # update the model to the actual value if an alias has been passed in
-        if self.routing_strategy == "least-busy":
-            if len(self.healthy_deployments) > 0:
-                for item in self.healthy_deployments:
-                    if item[0]["model_name"] == model: # first one in queue will be the one with the most availability
-                        return item[0]
+        if self.routing_strategy == "least-busy" and self.leastbusy_logger is not None:
+            deployments = self.leastbusy_logger.get_available_deployments(model_group=model)
+            # pick least busy deployment
+            min_traffic = float('inf')
+            min_deployment = None
+            for k, v in deployments.items(): 
+                if v < min_traffic:
+                    min_deployment = k
+            ############## No Available Deployments passed, we do a random pick #################
+            if min_deployment is None: 
+                min_deployment = random.choice(healthy_deployments)
+            ############## Available Deployments passed, we find the relevant item #################
             else: 
-                raise ValueError("No models available.")
+                for m in healthy_deployments: 
+                    if m["model_info"]["id"] == min_deployment:
+                        return m
+                min_deployment = random.choice(healthy_deployments)
+            return min_deployment 
         elif self.routing_strategy == "simple-shuffle": 
             # if users pass rpm or tpm, we do a random weighted pick - based on rpm/tpm
             ############## Check if we can do a RPM/TPM based weighted pick #################

litellm/router_strategy/least_busy.py

@@ -0,0 +1,96 @@
+#### What this does ####
+#   identifies least busy deployment
+#   How is this achieved? 
+#   - Before each call, have the router print the state of requests {"deployment": "requests_in_flight"}
+#   - use litellm.input_callbacks to log when a request is just about to be made to a model - {"deployment-id": traffic}
+#   - use litellm.success + failure callbacks to log when a request completed 
+#   - in get_available_deployment, for a given model group name -> pick based on traffic
+
+import dotenv, os, requests
+from typing import Optional
+dotenv.load_dotenv()  # Loading env variables using dotenv
+import traceback
+from litellm.caching import DualCache
+from litellm.integrations.custom_logger import CustomLogger
+
+class LeastBusyLoggingHandler(CustomLogger):
+
+    def __init__(self, router_cache: DualCache):
+        self.router_cache = router_cache
+        self.mapping_deployment_to_id: dict = {} 
+
+
+    def log_pre_api_call(self, model, messages, kwargs):
+        """
+        Log when a model is being used. 
+
+        Caching based on model group. 
+        """
+        try: 
+
+            if kwargs['litellm_params'].get('metadata') is None: 
+                pass
+            else: 
+                deployment = kwargs['litellm_params']['metadata'].get('deployment', None)
+                model_group = kwargs['litellm_params']['metadata'].get('model_group', None)
+                id = kwargs['litellm_params'].get('model_info', {}).get('id', None)
+                if deployment is None or model_group is None or id is None:
+                    return
+                
+                # map deployment to id
+                self.mapping_deployment_to_id[deployment] = id
+                
+                request_count_api_key = f"{model_group}_request_count"
+                # update cache
+                request_count_dict = self.router_cache.get_cache(key=request_count_api_key) or {} 
+                request_count_dict[deployment] = request_count_dict.get(deployment, 0) + 1
+                self.router_cache.set_cache(key=request_count_api_key, value=request_count_dict)
+        except Exception as e:
+            pass
+
+    async def async_log_success_event(self, kwargs, response_obj, start_time, end_time):
+        try:
+            if kwargs['litellm_params'].get('metadata') is None: 
+                pass
+            else: 
+                deployment = kwargs['litellm_params']['metadata'].get('deployment', None)
+                model_group = kwargs['litellm_params']['metadata'].get('model_group', None)
+                if deployment is None or model_group is None:
+                    return
+                
+                
+                request_count_api_key = f"{model_group}_request_count"
+                # decrement count in cache
+                request_count_dict = self.router_cache.get_cache(key=request_count_api_key) or {} 
+                request_count_dict[deployment] = request_count_dict.get(deployment)
+                self.router_cache.set_cache(key=request_count_api_key, value=request_count_dict)
+        except Exception as e:
+            pass
+
+    async def async_log_failure_event(self, kwargs, response_obj, start_time, end_time):
+        try:
+            if kwargs['litellm_params'].get('metadata') is None: 
+                pass
+            else: 
+                deployment = kwargs['litellm_params']['metadata'].get('deployment', None)
+                model_group = kwargs['litellm_params']['metadata'].get('model_group', None)
+                if deployment is None or model_group is None:
+                    return
+                
+                
+                request_count_api_key = f"{model_group}_request_count"
+                # decrement count in cache
+                request_count_dict = self.router_cache.get_cache(key=request_count_api_key) or {} 
+                request_count_dict[deployment] = request_count_dict.get(deployment)
+                self.router_cache.set_cache(key=request_count_api_key, value=request_count_dict)
+        except Exception as e:
+            pass
+
+    def get_available_deployments(self, model_group: str):
+        request_count_api_key = f"{model_group}_request_count"
+        request_count_dict = self.router_cache.get_cache(key=request_count_api_key) or {}
+        # map deployment to id
+        return_dict = {}
+        for key, value in request_count_dict.items():
+            return_dict[self.mapping_deployment_to_id[key]] = value
+        return return_dict

litellm/tests/test_least_busy_routing.py

@@ -0,0 +1,79 @@
+# #### What this tests ####
+# #    This tests the router's ability to identify the least busy deployment
+
+# #
+# # How is this achieved? 
+# # - Before each call, have the router print the state of requests {"deployment": "requests_in_flight"}
+# # - use litellm.input_callbacks to log when a request is just about to be made to a model - {"deployment-id": traffic}
+# # - use litellm.success + failure callbacks to log when a request completed 
+# # - in get_available_deployment, for a given model group name -> pick based on traffic
+
+# import sys, os, asyncio, time
+# import traceback
+# from dotenv import load_dotenv
+
+# load_dotenv()
+# import os
+
+# sys.path.insert(
+#     0, os.path.abspath("../..")
+# )  # Adds the parent directory to the system path
+# import pytest
+# from litellm import Router
+# import litellm
+
+# async def test_least_busy_routing():
+#     model_list = [{
+#         "model_name": "azure-model",
+#         "litellm_params": {
+#             "model": "azure/gpt-turbo",
+#             "api_key": "os.environ/AZURE_FRANCE_API_KEY",
+#             "api_base": "https://openai-france-1234.openai.azure.com",
+#             "rpm": 1440,
+#         }
+#     }, {
+#         "model_name": "azure-model",
+#         "litellm_params": {
+#             "model": "azure/gpt-35-turbo",
+#             "api_key": "os.environ/AZURE_EUROPE_API_KEY",
+#             "api_base": "https://my-endpoint-europe-berri-992.openai.azure.com",
+#             "rpm": 6
+#         }
+#     }, {
+#         "model_name": "azure-model",
+#         "litellm_params": {
+#             "model": "azure/gpt-35-turbo",
+#             "api_key": "os.environ/AZURE_CANADA_API_KEY",
+#             "api_base": "https://my-endpoint-canada-berri992.openai.azure.com",
+#             "rpm": 6
+#         }
+#     }]
+#     router = Router(model_list=model_list, 
+# 					routing_strategy="least-busy",
+# 					set_verbose=False,
+#                     num_retries=3) # type: ignore
+    
+#     async def call_azure_completion():
+#         try: 
+#             response = await router.acompletion(
+#                 model="azure-model",
+#                 messages=[
+#                     {
+#                         "role": "user",
+#                         "content": "hello this request will pass"
+#                     }
+#                 ]
+#             )
+#             print("\n response", response)
+#             return response
+#         except: 
+#             return None
+    
+#     n = 1000
+#     start_time = time.time()
+#     tasks = [call_azure_completion() for _ in range(n)]
+#     chat_completions = await asyncio.gather(*tasks)
+#     successful_completions = [c for c in chat_completions if c is not None]
+#     print(n, time.time() - start_time, len(successful_completions))
+
+# asyncio.run(test_least_busy_routing())

litellm/tests/test_router.py

@@ -226,10 +226,12 @@ def test_call_one_endpoint():
 			)
 
 			print("\n response", response)
+		tasks = []
+		tasks.append(call_azure_completion())
+		tasks.append(call_bedrock_claude())
+		tasks.append(call_azure_embedding())
 
-		asyncio.run(call_azure_completion())
-		asyncio.run(call_bedrock_claude())
-		asyncio.run(call_azure_embedding())
+		asyncio.gather(**tasks)
 		
 		os.environ["AZURE_API_BASE"] = old_api_base
 		os.environ["AZURE_API_KEY"] = old_api_key

litellm/utils.py

@@ -562,19 +562,25 @@ class Logging:
             **self.optional_params
         }
 
+    def _pre_call(self, input, api_key, model=None, additional_args={}): 
+        """
+        Common helper function across the sync + async pre-call function
+        """
+        # print_verbose(f"logging pre call for model: {self.model} with call type: {self.call_type}")
+        self.model_call_details["input"] = input
+        self.model_call_details["api_key"] = api_key
+        self.model_call_details["additional_args"] = additional_args
+        self.model_call_details["log_event_type"] = "pre_api_call"
+        if (
+                model
+            ):  # if model name was changes pre-call, overwrite the initial model call name with the new one
+                self.model_call_details["model"] = model
+
     def pre_call(self, input, api_key, model=None, additional_args={}):
         # Log the exact input to the LLM API
         litellm.error_logs['PRE_CALL'] = locals()
         try:
-            # print_verbose(f"logging pre call for model: {self.model} with call type: {self.call_type}")
-            self.model_call_details["input"] = input
-            self.model_call_details["api_key"] = api_key
-            self.model_call_details["additional_args"] = additional_args
-            self.model_call_details["log_event_type"] = "pre_api_call"
-            if (
-                model
-            ):  # if model name was changes pre-call, overwrite the initial model call name with the new one
-                self.model_call_details["model"] = model
+            self._pre_call(input=input, api_key=api_key, model=model, additional_args=additional_args)
 
             # User Logging -> if you pass in a custom logging function
             headers = additional_args.get("headers", {})
@@ -688,6 +694,34 @@ class Logging:
             if capture_exception:  # log this error to sentry for debugging
                 capture_exception(e)
 
+    async def async_pre_call(self, result=None, start_time=None, end_time=None, **kwargs):
+        """
+       Â Implementing async callbacks, to handle asyncio event loop issues when custom integrations need to use async functions.
+        """
+        start_time, end_time, result, complete_streaming_response = self._success_handler_helper_fn(start_time=start_time, end_time=end_time, result=result)
+        print_verbose(f"Async input callbacks: {litellm._async_input_callback}")
+        for callback in litellm._async_input_callback:
+            try: 
+                if isinstance(callback, CustomLogger): # custom logger class 
+                    print_verbose(f"Async input callbacks: CustomLogger")
+                    asyncio.create_task(callback.async_log_input_event(
+                            model=self.model,
+                            messages=self.messages,
+                            kwargs=self.model_call_details,
+                        ))
+                if callable(callback): # custom logger functions
+                    print_verbose(f"Async success callbacks: async_log_event")
+                    asyncio.create_task(customLogger.async_log_input_event(
+                        model=self.model,
+                        messages=self.messages,
+                        kwargs=self.model_call_details,
+                        print_verbose=print_verbose,
+                        callback_func=callback
+                    ))
+            except: 
+                print_verbose(
+                    f"LiteLLM.LoggingError: [Non-Blocking] Exception occurred while success logging {traceback.format_exc()}"
+                )
     def post_call(self, original_response, input=None, api_key=None,  additional_args={}):
         # Log the exact result from the LLM API, for streaming - log the type of response received
         litellm.error_logs['POST_CALL'] = locals()
@@ -1289,6 +1323,17 @@ def client(original_function):
                     function_id=function_id
                 )
             ## ASYNC CALLBACKS
+            if len(litellm.input_callback) > 0:
+                removed_async_items = []
+                for index, callback in enumerate(litellm.input_callback):
+                    if inspect.iscoroutinefunction(callback):
+                        litellm._async_input_callback.append(callback)
+                        removed_async_items.append(index)
+
+                # Pop the async items from input_callback in reverse order to avoid index issues
+                for index in reversed(removed_async_items):
+                    litellm.input_callback.pop(index)
+
             if len(litellm.success_callback) > 0: 
                 removed_async_items = []
                 for index, callback in enumerate(litellm.success_callback): 
@@ -1307,7 +1352,7 @@ def client(original_function):
                         litellm._async_failure_callback.append(callback)
                         removed_async_items.append(index)
 
-                # Pop the async items from success_callback in reverse order to avoid index issues
+                # Pop the async items from failure_callback in reverse order to avoid index issues
                 for index in reversed(removed_async_items):
                     litellm.failure_callback.pop(index)
             if add_breadcrumb: