feat: add VLLMProvider (#1866)

Co-authored-by: cpacker <packercharles@gmail.com>

letta/cli/cli.py

@@ -14,9 +14,7 @@
 from letta.local_llm.constants import ASSISTANT_MESSAGE_CLI_SYMBOL
 from letta.log import get_logger
 from letta.metadata import MetadataStore
-from letta.schemas.embedding_config import EmbeddingConfig
 from letta.schemas.enums import OptionState
-from letta.schemas.llm_config import LLMConfig
 from letta.schemas.memory import ChatMemory, Memory
 from letta.server.server import logger as server_logger
 
@@ -235,12 +233,7 @@ def run(
         # choose from list of llm_configs
         llm_configs = client.list_llm_configs()
         llm_options = [llm_config.model for llm_config in llm_configs]
-
-        # TODO move into LLMConfig as a class method?
-        def prettify_llm_config(llm_config: LLMConfig) -> str:
-            return f"{llm_config.model}" + f" ({llm_config.model_endpoint})" if llm_config.model_endpoint else ""
-
-        llm_choices = [questionary.Choice(title=prettify_llm_config(llm_config), value=llm_config) for llm_config in llm_configs]
+        llm_choices = [questionary.Choice(title=llm_config.pretty_print(), value=llm_config) for llm_config in llm_configs]
 
         # select model
         if len(llm_options) == 0:
@@ -255,17 +248,8 @@ def prettify_llm_config(llm_config: LLMConfig) -> str:
         embedding_configs = client.list_embedding_configs()
         embedding_options = [embedding_config.embedding_model for embedding_config in embedding_configs]
 
-        # TODO move into EmbeddingConfig as a class method?
-        def prettify_embed_config(embedding_config: EmbeddingConfig) -> str:
-            return (
-                f"{embedding_config.embedding_model}" + f" ({embedding_config.embedding_endpoint})"
-                if embedding_config.embedding_endpoint
-                else ""
-            )
-
         embedding_choices = [
-            questionary.Choice(title=prettify_embed_config(embedding_config), value=embedding_config)
-            for embedding_config in embedding_configs
+            questionary.Choice(title=embedding_config.pretty_print(), value=embedding_config) for embedding_config in embedding_configs
         ]
 
         # select model

letta/llm_api/llm_api_tools.py

@@ -70,6 +70,10 @@ def wrapper(*args, **kwargs):
                 return func(*args, **kwargs)
 
             except requests.exceptions.HTTPError as http_err:
+
+                if not hasattr(http_err, "response") or not http_err.response:
+                    raise
+
                 # Retry on specified errors
                 if http_err.response.status_code in error_codes:
                     # Increment retries

letta/llm_api/openai.py

@@ -61,6 +61,7 @@ def openai_get_model_list(
         headers["Authorization"] = f"Bearer {api_key}"
 
     printd(f"Sending request to {url}")
+    response = None
     try:
         # TODO add query param "tool" to be true
         response = requests.get(url, headers=headers, params=extra_params)
@@ -71,23 +72,26 @@ def openai_get_model_list(
     except requests.exceptions.HTTPError as http_err:
         # Handle HTTP errors (e.g., response 4XX, 5XX)
         try:
-            response = response.json()
+            if response:
+                response = response.json()
         except:
             pass
         printd(f"Got HTTPError, exception={http_err}, response={response}")
         raise http_err
     except requests.exceptions.RequestException as req_err:
         # Handle other requests-related errors (e.g., connection error)
         try:
-            response = response.json()
+            if response:
+                response = response.json()
         except:
             pass
         printd(f"Got RequestException, exception={req_err}, response={response}")
         raise req_err
     except Exception as e:
         # Handle other potential errors
         try:
-            response = response.json()
+            if response:
+                response = response.json()
         except:
             pass
         printd(f"Got unknown Exception, exception={e}, response={response}")

letta/local_llm/vllm/api.py

@@ -3,7 +3,7 @@
 from letta.local_llm.settings.settings import get_completions_settings
 from letta.local_llm.utils import count_tokens, post_json_auth_request
 
-WEBUI_API_SUFFIX = "/v1/completions"
+WEBUI_API_SUFFIX = "/completions"
 
 
 def get_vllm_completion(endpoint, auth_type, auth_key, model, prompt, context_window, user, grammar=None):

letta/providers.py

@@ -14,14 +14,18 @@
 
 class Provider(BaseModel):
 
-    def list_llm_models(self):
+    def list_llm_models(self) -> List[LLMConfig]:
         return []
 
-    def list_embedding_models(self):
+    def list_embedding_models(self) -> List[EmbeddingConfig]:
         return []
 
-    def get_model_context_window(self, model_name: str):
-        pass
+    def get_model_context_window(self, model_name: str) -> Optional[int]:
+        raise NotImplementedError
+
+    def provider_tag(self) -> str:
+        """String representation of the provider for display purposes"""
+        raise NotImplementedError
 
 
 class LettaProvider(Provider):
@@ -162,7 +166,7 @@ def list_llm_models(self) -> List[LLMConfig]:
             )
         return configs
 
-    def get_model_context_window(self, model_name: str):
+    def get_model_context_window(self, model_name: str) -> Optional[int]:
 
         import requests
 
@@ -310,7 +314,7 @@ def list_embedding_models(self):
             )
         return configs
 
-    def get_model_context_window(self, model_name: str):
+    def get_model_context_window(self, model_name: str) -> Optional[int]:
         from letta.llm_api.google_ai import google_ai_get_model_context_window
 
         return google_ai_get_model_context_window(self.base_url, self.api_key, model_name)
@@ -371,16 +375,75 @@ def list_embedding_models(self) -> List[EmbeddingConfig]:
             )
         return configs
 
-    def get_model_context_window(self, model_name: str):
+    def get_model_context_window(self, model_name: str) -> Optional[int]:
         """
         This is hardcoded for now, since there is no API endpoints to retrieve metadata for a model.
         """
         return AZURE_MODEL_TO_CONTEXT_LENGTH.get(model_name, 4096)
 
 
-class VLLMProvider(OpenAIProvider):
+class VLLMChatCompletionsProvider(Provider):
+    """vLLM provider that treats vLLM as an OpenAI /chat/completions proxy"""
+
     # NOTE: vLLM only serves one model at a time (so could configure that through env variables)
-    pass
+    name: str = "vllm"
+    base_url: str = Field(..., description="Base URL for the vLLM API.")
+
+    def list_llm_models(self) -> List[LLMConfig]:
+        # not supported with vLLM
+        from letta.llm_api.openai import openai_get_model_list
+
+        assert self.base_url, "base_url is required for vLLM provider"
+        response = openai_get_model_list(self.base_url, api_key=None)
+
+        configs = []
+        print(response)
+        for model in response["data"]:
+            configs.append(
+                LLMConfig(
+                    model=model["id"],
+                    model_endpoint_type="openai",
+                    model_endpoint=self.base_url,
+                    context_window=model["max_model_len"],
+                )
+            )
+        return configs
+
+    def list_embedding_models(self) -> List[EmbeddingConfig]:
+        # not supported with vLLM
+        return []
+
+
+class VLLMCompletionsProvider(Provider):
+    """This uses /completions API as the backend, not /chat/completions, so we need to specify a model wrapper"""
+
+    # NOTE: vLLM only serves one model at a time (so could configure that through env variables)
+    name: str = "vllm"
+    base_url: str = Field(..., description="Base URL for the vLLM API.")
+    default_prompt_formatter: str = Field(..., description="Default prompt formatter (aka model wrapper)to use on vLLM /completions API.")
+
+    def list_llm_models(self) -> List[LLMConfig]:
+        # not supported with vLLM
+        from letta.llm_api.openai import openai_get_model_list
+
+        response = openai_get_model_list(self.base_url, api_key=None)
+
+        configs = []
+        for model in response["data"]:
+            configs.append(
+                LLMConfig(
+                    model=model["id"],
+                    model_endpoint_type="vllm",
+                    model_endpoint=self.base_url,
+                    model_wrapper=self.default_prompt_formatter,
+                    context_window=model["max_model_len"],
+                )
+            )
+        return configs
+
+    def list_embedding_models(self) -> List[EmbeddingConfig]:
+        # not supported with vLLM
+        return []
 
 
 class CohereProvider(OpenAIProvider):

letta/schemas/embedding_config.py

@@ -52,3 +52,10 @@ def default_config(cls, model_name: Optional[str] = None, provider: Optional[str
             )
         else:
             raise ValueError(f"Model {model_name} not supported.")
+
+    def pretty_print(self) -> str:
+        return (
+            f"{self.embedding_model}"
+            + (f" [type={self.embedding_endpoint_type}]" if self.embedding_endpoint_type else "")
+            + (f" [ip={self.embedding_endpoint}]" if self.embedding_endpoint else "")
+        )

letta/schemas/llm_config.py

@@ -68,3 +68,10 @@ def default_config(cls, model_name: str):
             )
         else:
             raise ValueError(f"Model {model_name} not supported.")
+
+    def pretty_print(self) -> str:
+        return (
+            f"{self.model}"
+            + (f" [type={self.model_endpoint_type}]" if self.model_endpoint_type else "")
+            + (f" [ip={self.model_endpoint}]" if self.model_endpoint else "")
+        )

letta/server/server.py

@@ -51,7 +51,8 @@
     OllamaProvider,
     OpenAIProvider,
     Provider,
-    VLLMProvider,
+    VLLMChatCompletionsProvider,
+    VLLMCompletionsProvider,
 )
 from letta.schemas.agent import AgentState, AgentType, CreateAgent, UpdateAgentState
 from letta.schemas.api_key import APIKey, APIKeyCreate
@@ -244,19 +245,30 @@ def __init__(
         if model_settings.anthropic_api_key:
             self._enabled_providers.append(AnthropicProvider(api_key=model_settings.anthropic_api_key))
         if model_settings.ollama_base_url:
-            self._enabled_providers.append(OllamaProvider(base_url=model_settings.ollama_base_url))
-        if model_settings.vllm_base_url:
-            self._enabled_providers.append(VLLMProvider(base_url=model_settings.vllm_base_url))
+            self._enabled_providers.append(OllamaProvider(base_url=model_settings.ollama_base_url, api_key=None))
         if model_settings.gemini_api_key:
             self._enabled_providers.append(GoogleAIProvider(api_key=model_settings.gemini_api_key))
         if model_settings.azure_api_key and model_settings.azure_base_url:
+            assert model_settings.azure_api_version, "AZURE_API_VERSION is required"
             self._enabled_providers.append(
                 AzureProvider(
                     api_key=model_settings.azure_api_key,
                     base_url=model_settings.azure_base_url,
                     api_version=model_settings.azure_api_version,
                 )
             )
+        if model_settings.vllm_api_base:
+            # vLLM exposes both a /chat/completions and a /completions endpoint
+            self._enabled_providers.append(
+                VLLMCompletionsProvider(
+                    base_url=model_settings.vllm_api_base,
+                    default_prompt_formatter=model_settings.default_prompt_formatter,
+                )
+            )
+            # NOTE: to use the /chat/completions endpoint, you need to specify extra flags on vLLM startup
+            # see: https://docs.vllm.ai/en/latest/getting_started/examples/openai_chat_completion_client_with_tools.html
+            # e.g. "... --enable-auto-tool-choice --tool-call-parser hermes"
+            self._enabled_providers.append(VLLMChatCompletionsProvider(base_url=model_settings.vllm_api_base))
 
     def save_agents(self):
         """Saves all the agents that are in the in-memory object store"""

letta/settings.py

@@ -4,14 +4,20 @@
 from pydantic import Field
 from pydantic_settings import BaseSettings, SettingsConfigDict
 
+from letta.local_llm.constants import DEFAULT_WRAPPER_NAME
+
 
 class ModelSettings(BaseSettings):
 
     # env_prefix='my_prefix_'
 
+    # when we use /completions APIs (instead of /chat/completions), we need to specify a model wrapper
+    # the "model wrapper" is responsible for prompt formatting and function calling parsing
+    default_prompt_formatter: str = DEFAULT_WRAPPER_NAME
+
     # openai
     openai_api_key: Optional[str] = None
-    openai_api_base: Optional[str] = "https://api.openai.com/v1"
+    openai_api_base: str = "https://api.openai.com/v1"
 
     # groq
     groq_api_key: Optional[str] = None
@@ -34,7 +40,7 @@ class ModelSettings(BaseSettings):
     gemini_api_key: Optional[str] = None
 
     # vLLM
-    vllm_base_url: Optional[str] = None
+    vllm_api_base: Optional[str] = None
 
     # openllm
     openllm_auth_type: Optional[str] = None

tests/test_providers.py

@@ -52,3 +52,11 @@ def test_googleai():
     print(models)
 
     provider.list_embedding_models()
+
+
+# def test_vllm():
+#    provider = VLLMProvider(base_url=os.getenv("VLLM_API_BASE"))
+#    models = provider.list_llm_models()
+#    print(models)
+#
+#    provider.list_embedding_models()