langchain_ollama: Support keep_alive in embeddings (#30251)

- Description: Adds support for keep_alive in Ollama Embeddings see
https://github.com/ollama/ollama/issues/6401.
Builds on top of of
https://github.com/langchain-ai/langchain/pull/29296. I have this use
case where I want to keep the embeddings model in cpu forever.
- Dependencies: no deps are being introduced.
- Issue: haven't created an issue yet.

libs/partners/ollama/langchain_ollama/embeddings.py

@@ -164,6 +164,11 @@ class OllamaEmbeddings(BaseModel, Embeddings):
     """The number of GPUs to use. On macOS it defaults to 1 to
     enable metal support, 0 to disable."""
 
+    keep_alive: Optional[int] = None
+    """controls how long the model will stay loaded into memory
+    following the request (default: 5m)
+    """
+
     num_thread: Optional[int] = None
     """Sets the number of threads to use during computation.
     By default, Ollama will detect this for optimal performance.
@@ -235,7 +240,7 @@ class OllamaEmbeddings(BaseModel, Embeddings):
     def embed_documents(self, texts: List[str]) -> List[List[float]]:
         """Embed search docs."""
         embedded_docs = self._client.embed(
-            self.model, texts, options=self._default_params
+            self.model, texts, options=self._default_params, keep_alive=self.keep_alive
         )["embeddings"]
         return embedded_docs
 
@@ -245,9 +250,11 @@ class OllamaEmbeddings(BaseModel, Embeddings):
 
     async def aembed_documents(self, texts: List[str]) -> List[List[float]]:
         """Embed search docs."""
-        embedded_docs = (await self._async_client.embed(self.model, texts))[
-            "embeddings"
-        ]
+        embedded_docs = (
+            await self._async_client.embed(
+                self.model, texts, keep_alive=self.keep_alive
+            )
+        )["embeddings"]
         return embedded_docs
 
     async def aembed_query(self, text: str) -> List[float]:

libs/partners/ollama/tests/unit_tests/test_embeddings.py

@@ -5,4 +5,4 @@ from langchain_ollama.embeddings import OllamaEmbeddings
 
 def test_initialization() -> None:
     """Test embedding model initialization."""
-    OllamaEmbeddings(model="llama3")
+    OllamaEmbeddings(model="llama3", keep_alive=1)