refac: modularize backend IV

backends/sessions.py

@@ -0,0 +1,72 @@
+"""aiohttp / OpenAI client factories aware of Unix-socket endpoints.
+
+Unix socket endpoints follow the ``.sock`` hostname convention (e.g.
+``http://192.168.0.52.sock/v1``) and resolve to ``/run/user/<uid>/<host>``.
+Their sessions/clients live in ``state.app_state`` so that startup can
+populate them once and routes can reuse them.
+"""
+import os
+
+import aiohttp
+import openai
+
+from state import app_state
+from backends.normalize import ep2base
+
+
+def _is_unix_socket_endpoint(endpoint: str) -> bool:
+    """Return True if endpoint uses Unix socket (.sock hostname convention).
+
+    Detects URLs like http://192.168.0.52.sock/v1 where the host ends with
+    .sock, indicating the connection should use a Unix domain socket at
+    /tmp/<host> instead of TCP.
+    """
+    try:
+        host = endpoint.split("//", 1)[1].split("/")[0].split(":")[0]
+        return host.endswith(".sock")
+    except IndexError:
+        return False
+
+
+def _get_socket_path(endpoint: str) -> str:
+    """Derive Unix socket file path from a .sock endpoint URL.
+
+    http://192.168.0.52.sock/v1 -> /run/user/<uid>/192.168.0.52.sock
+    """
+    host = endpoint.split("//", 1)[1].split("/")[0].split(":")[0]
+    return f"/run/user/{os.getuid()}/{host}"
+
+
+def get_session(endpoint: str) -> aiohttp.ClientSession:
+    """Return the appropriate aiohttp session for the given endpoint.
+
+    Unix socket endpoints (.sock) get their own UnixConnector session.
+    All other endpoints share the main TCP session.
+    """
+    if _is_unix_socket_endpoint(endpoint):
+        sess = app_state["socket_sessions"].get(endpoint)
+        if sess is not None:
+            return sess
+    return app_state["session"]
+
+
+def _make_openai_client(
+    endpoint: str,
+    default_headers: dict | None = None,
+    api_key: str = "no-key",
+) -> openai.AsyncOpenAI:
+    """Return an AsyncOpenAI client configured for the given endpoint.
+
+    For Unix socket endpoints, injects a pre-created httpx UDS transport
+    so the OpenAI SDK connects via the socket instead of TCP.
+    """
+    base_url = ep2base(endpoint)
+    kwargs: dict = {"api_key": api_key}
+    if default_headers is not None:
+        kwargs["default_headers"] = default_headers
+    if _is_unix_socket_endpoint(endpoint):
+        http_client = app_state["httpx_clients"].get(endpoint)
+        if http_client is not None:
+            kwargs["http_client"] = http_client
+            base_url = "http://localhost/v1"
+    return openai.AsyncOpenAI(base_url=base_url, **kwargs)