community[patch]: OllamaEmbeddings - Pass headers to post request (#16880)

## Feature
- Set additional headers in constructor
- Headers will be sent in post request

This feature is useful if deploying Ollama on a cloud service such as
hugging face, which requires authentication tokens to be passed in the
request header.

## Tests
- Test if header is passed
- Test if header is not passed

Similar to https://github.com/langchain-ai/langchain/pull/15881

---------

Co-authored-by: Bagatur <baskaryan@gmail.com>

libs/community/langchain_community/embeddings/ollama.py

@@ -105,6 +105,12 @@ class OllamaEmbeddings(BaseModel, Embeddings):
     show_progress: bool = False
     """Whether to show a tqdm progress bar. Must have `tqdm` installed."""
 
+    headers: Optional[dict] = None
+    """Additional headers to pass to endpoint (e.g. Authorization, Referer).
+    This is useful when Ollama is hosted on cloud services that require
+    tokens for authentication.
+    """
+
     @property
     def _default_params(self) -> Dict[str, Any]:
         """Get the default parameters for calling Ollama."""
@@ -151,6 +157,7 @@ class OllamaEmbeddings(BaseModel, Embeddings):
         """
         headers = {
             "Content-Type": "application/json",
+            **(self.headers or {}),
         }
 
         try:

libs/community/tests/unit_tests/embeddings/test_ollama.py

@@ -0,0 +1,61 @@
+import requests
+from pytest import MonkeyPatch
+
+from langchain_community.embeddings.ollama import OllamaEmbeddings
+
+
+class MockResponse:
+    status_code = 200
+
+    def json(self) -> dict:
+        return {"embedding": [1, 2, 3]}
+
+
+def mock_response() -> MockResponse:
+    return MockResponse()
+
+
+def test_pass_headers_if_provided(monkeypatch: MonkeyPatch) -> None:
+    embedder = OllamaEmbeddings(
+        base_url="https://ollama-hostname:8000",
+        model="foo",
+        headers={
+            "Authorization": "Bearer TEST-TOKEN-VALUE",
+            "Referer": "https://application-host",
+        },
+    )
+
+    def mock_post(url: str, headers: dict, json: str) -> MockResponse:
+        assert url == "https://ollama-hostname:8000/api/embeddings"
+        assert headers == {
+            "Content-Type": "application/json",
+            "Authorization": "Bearer TEST-TOKEN-VALUE",
+            "Referer": "https://application-host",
+        }
+        assert json is not None
+
+        return mock_response()
+
+    monkeypatch.setattr(requests, "post", mock_post)
+
+    embedder.embed_query("Test prompt")
+
+
+def test_handle_if_headers_not_provided(monkeypatch: MonkeyPatch) -> None:
+    embedder = OllamaEmbeddings(
+        base_url="https://ollama-hostname:8000",
+        model="foo",
+    )
+
+    def mock_post(url: str, headers: dict, json: str) -> MockResponse:
+        assert url == "https://ollama-hostname:8000/api/embeddings"
+        assert headers == {
+            "Content-Type": "application/json",
+        }
+        assert json is not None
+
+        return mock_response()
+
+    monkeypatch.setattr(requests, "post", mock_post)
+
+    embedder.embed_query("Test prompt")

libs/community/tests/unit_tests/llms/test_ollama.py

@@ -25,7 +25,7 @@ def test_pass_headers_if_provided(monkeypatch: MonkeyPatch) -> None:
         base_url="https://ollama-hostname:8000",
         model="foo",
         headers={
-            "Authentication": "Bearer TEST-TOKEN-VALUE",
+            "Authorization": "Bearer TEST-TOKEN-VALUE",
             "Referer": "https://application-host",
         },
         timeout=300,
@@ -35,7 +35,7 @@ def test_pass_headers_if_provided(monkeypatch: MonkeyPatch) -> None:
         assert url == "https://ollama-hostname:8000/api/generate"
         assert headers == {
             "Content-Type": "application/json",
-            "Authentication": "Bearer TEST-TOKEN-VALUE",
+            "Authorization": "Bearer TEST-TOKEN-VALUE",
             "Referer": "https://application-host",
         }
         assert json is not None