Fix issue #183

Fix issue #183: Pre-download models during server initialization to prevent HTTP timeouts

This commit moves the model downloading logic from the `chat_completion` method to the `initialize` method in `OllamaInferenceAdapter`. By pre-loading required models during server startup, we ensure that large models (e.g., 16GB) are downloaded before serving requests, thus preventing HTTP request timeouts and aborted downloads during the first inference request.

Closes #183.

llama_stack/providers/adapters/inference/ollama/ollama.py

@@ -9,7 +9,6 @@ from typing import AsyncGenerator
 import httpx
 
 from llama_models.llama3.api.chat_format import ChatFormat
-from llama_models.llama3.api.datatypes import Message, StopReason
 from llama_models.llama3.api.tokenizer import Tokenizer
 
 from ollama import AsyncClient
@@ -31,11 +30,12 @@ OLLAMA_SUPPORTED_SKUS = {
 
 
 class OllamaInferenceAdapter(Inference, RoutableProviderForModels):
-    def __init__(self, url: str) -> None:
+    def __init__(self, url: str, preload_models: List[str] = None) -> None:
         RoutableProviderForModels.__init__(
             self, stack_to_provider_models_map=OLLAMA_SUPPORTED_SKUS
         )
         self.url = url
+        self.preload_models = preload_models or []
         tokenizer = Tokenizer.get_instance()
         self.formatter = ChatFormat(tokenizer)
 
@@ -52,6 +52,23 @@ class OllamaInferenceAdapter(Inference, RoutableProviderForModels):
                 "Ollama Server is not running, start it using `ollama serve` in a separate terminal"
             ) from e
 
+        # Pre-download models
+        for model in self.preload_models:
+            ollama_model = self.map_to_provider_model(model)
+            res = await self.client.ps()
+            need_model_pull = True
+            for r in res["models"]:
+                if ollama_model == r["model"]:
+                    need_model_pull = False
+                    break
+
+            if need_model_pull:
+                print(f"Pulling model: {ollama_model}")
+                status = await self.client.pull(ollama_model)
+                assert (
+                    status["status"] == "success"
+                ), f"Failed to pull model {ollama_model} in ollama"
+
     async def shutdown(self) -> None:
         pass