[OAI Serving] Validate greedy generation args (#13113)

* validate greedy generation args

Signed-off-by: jenchen13 <jennifchen@nvidia.com>

Author: jenchen13

nemo/deploy/service/fastapi_interface_to_pytriton.py

@@ -14,7 +14,7 @@
 import numpy as np
 import requests
 from fastapi import FastAPI, HTTPException
-from pydantic import BaseModel
+from pydantic import BaseModel, model_validator
 from pydantic_settings import BaseSettings
 
 from nemo.deploy.nlp import NemoQueryLLMPyTorch
@@ -81,6 +81,14 @@ class CompletionRequest(BaseModel):
     top_k: int = 0
     logprobs: int = None
 
+    @model_validator(mode='after')
+    def set_greedy_params(self):
+        """Validate parameters for greedy decoding."""
+        if self.temperature == 0 and self.top_p == 0:
+            logging.warning("Both temperature and top_p are 0. Setting top_k to 1 to ensure greedy sampling.")
+            self.top_k = 1
+        return self
+
 
 @app.get("/v1/health")
 def health_check():