Hermes-agent
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Zakaria
@@ -0,0 +1,296 @@
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"""HTTP server that forwards OpenAI-compatible requests to a configured upstream.
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Listens on ``http://<host>:<port>/v1/<path>`` and forwards each request to
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``<upstream-base-url>/<path>`` with the client's ``Authorization`` header
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replaced by a freshly-resolved bearer from the configured adapter. The
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response is streamed back unmodified, preserving SSE.
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The server is intentionally minimal: it does NOT mediate, log, transform,
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or rewrite request/response bodies. It's a credential-attaching forwarder.
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"""
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from __future__ import annotations
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import asyncio
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import logging
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import signal
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from typing import Optional
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try:
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import aiohttp
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from aiohttp import web
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AIOHTTP_AVAILABLE = True
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except ImportError:
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aiohttp = None # type: ignore[assignment]
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web = None # type: ignore[assignment]
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AIOHTTP_AVAILABLE = False
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from hermes_cli.proxy.adapters.base import UpstreamAdapter, UpstreamCredential
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logger = logging.getLogger(__name__)
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# Headers we strip when forwarding to the upstream. ``host``/``content-length``
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# are recomputed by aiohttp; ``authorization`` is replaced with our bearer.
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# Everything else (content-type, accept, user-agent, x-* headers) passes through.
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_HOP_BY_HOP_HEADERS = frozenset(
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{
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"host",
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"content-length",
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"connection",
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"keep-alive",
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"proxy-authenticate",
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"proxy-authorization",
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"te",
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"trailers",
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"transfer-encoding",
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"upgrade",
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"authorization", # we replace this one
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}
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)
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DEFAULT_PORT = 8645
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DEFAULT_HOST = "127.0.0.1"
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def _json_error(status: int, message: str, code: str = "proxy_error") -> "web.Response":
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"""Return an OpenAI-style error JSON response."""
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body = {"error": {"message": message, "type": code, "code": code}}
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return web.json_response(body, status=status)
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def _filter_request_headers(headers: "aiohttp.typedefs.LooseHeaders") -> dict:
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"""Strip hop-by-hop + auth headers from the inbound request."""
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out = {}
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for key, value in headers.items():
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if key.lower() in _HOP_BY_HOP_HEADERS:
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continue
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out[key] = value
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return out
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def _filter_response_headers(headers) -> dict:
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"""Strip hop-by-hop headers from the upstream response."""
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out = {}
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for key, value in headers.items():
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if key.lower() in _HOP_BY_HOP_HEADERS:
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continue
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# aiohttp recomputes Content-Encoding/Content-Length on stream — let it.
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if key.lower() in {"content-encoding", "content-length"}:
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continue
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out[key] = value
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return out
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def create_app(adapter: UpstreamAdapter) -> "web.Application":
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"""Build the aiohttp application bound to a specific upstream adapter."""
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if not AIOHTTP_AVAILABLE:
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raise RuntimeError(
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"aiohttp is required for `hermes proxy`. Install with: "
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"pip install 'hermes-agent[messaging]' or `pip install aiohttp`."
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)
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app = web.Application()
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# AppKey ensures forward-compat with future aiohttp versions that strip
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# bare-string keys.
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_adapter_key = web.AppKey("adapter", UpstreamAdapter)
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app[_adapter_key] = adapter
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async def handle_health(request: "web.Request") -> "web.Response":
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return web.json_response(
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{
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"status": "ok",
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"upstream": adapter.display_name,
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"authenticated": adapter.is_authenticated(),
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}
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)
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async def handle_proxy(request: "web.Request") -> "web.StreamResponse":
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# Extract the path *after* /v1
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rel_path = request.match_info.get("tail", "")
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rel_path = "/" + rel_path.lstrip("/")
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if rel_path not in adapter.allowed_paths:
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allowed = ", ".join(sorted(adapter.allowed_paths))
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return _json_error(
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404,
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f"Path /v1{rel_path} is not forwarded by this proxy. "
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f"Allowed: {allowed}",
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code="path_not_allowed",
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)
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try:
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cred = adapter.get_credential()
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except Exception as exc:
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logger.warning("proxy: credential resolution failed: %s", exc)
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return _json_error(401, str(exc), code="upstream_auth_failed")
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# Forward body verbatim. Read into memory once — request bodies for
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# chat/completions/embeddings are small (<1MB typically). If we ever
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# need to forward large multipart uploads we'll switch to streaming
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# the request body too.
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body = await request.read()
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timeout = aiohttp.ClientTimeout(total=None, sock_connect=15, sock_read=300)
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async def _send_upstream(active_cred: UpstreamCredential):
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upstream_url = f"{active_cred.base_url.rstrip('/')}{rel_path}"
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# Preserve query string verbatim.
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if request.query_string:
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upstream_url = f"{upstream_url}?{request.query_string}"
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fwd_headers = _filter_request_headers(request.headers)
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fwd_headers["Authorization"] = f"{active_cred.token_type} {active_cred.bearer}"
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logger.debug(
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"proxy: forwarding %s %s -> %s (body=%d bytes)",
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request.method, rel_path, upstream_url, len(body),
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)
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try:
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session = aiohttp.ClientSession(timeout=timeout)
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except Exception as exc: # pragma: no cover - aiohttp setup issue
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raise RuntimeError(f"proxy session init failed: {exc}") from exc
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try:
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upstream_resp = await session.request(
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request.method,
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upstream_url,
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data=body if body else None,
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headers=fwd_headers,
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allow_redirects=False,
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)
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except Exception:
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await session.close()
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raise
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return session, upstream_resp
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async def _open_upstream(active_cred: UpstreamCredential):
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try:
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return await _send_upstream(active_cred)
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except RuntimeError as exc:
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return _json_error(500, str(exc)), None
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except aiohttp.ClientError as exc:
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logger.warning("proxy: upstream connection failed: %s", exc)
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return (
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_json_error(
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502,
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f"upstream connection failed: {exc}",
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code="upstream_unreachable",
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),
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None,
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)
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except asyncio.TimeoutError:
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return (
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_json_error(
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504,
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"upstream request timed out",
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code="upstream_timeout",
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),
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None,
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)
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session_or_response, upstream_resp = await _open_upstream(cred)
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if upstream_resp is None:
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return session_or_response
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session = session_or_response
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if upstream_resp.status in {401, 429}:
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try:
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retry_cred = adapter.get_retry_credential(
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failed_credential=cred,
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status_code=upstream_resp.status,
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)
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except Exception as exc:
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logger.warning("proxy: retry credential resolution failed: %s", exc)
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retry_cred = None
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if retry_cred is not None:
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upstream_resp.release()
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await session.close()
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session_or_response, upstream_resp = await _open_upstream(retry_cred)
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if upstream_resp is None:
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return session_or_response
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session = session_or_response
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# Stream response back. Headers first, then chunked body.
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resp = web.StreamResponse(
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status=upstream_resp.status,
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headers=_filter_response_headers(upstream_resp.headers),
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)
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await resp.prepare(request)
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try:
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async for chunk in upstream_resp.content.iter_any():
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if chunk:
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await resp.write(chunk)
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except (aiohttp.ClientError, asyncio.CancelledError) as exc:
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logger.warning("proxy: streaming interrupted: %s", exc)
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finally:
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upstream_resp.release()
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await session.close()
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await resp.write_eof()
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return resp
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# /health doesn't go through the upstream
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app.router.add_get("/health", handle_health)
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# Catch-all under /v1 — forwards if the path is allowed.
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app.router.add_route("*", "/v1/{tail:.*}", handle_proxy)
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return app
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async def run_server(
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adapter: UpstreamAdapter,
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host: str = DEFAULT_HOST,
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port: int = DEFAULT_PORT,
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shutdown_event: Optional[asyncio.Event] = None,
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) -> None:
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"""Run the proxy in the current event loop until shutdown_event is set.
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If shutdown_event is None, runs until cancelled (Ctrl+C or SIGTERM).
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"""
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if not AIOHTTP_AVAILABLE:
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raise RuntimeError(
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"aiohttp is required for `hermes proxy`. Install with: "
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"pip install 'hermes-agent[messaging]' or `pip install aiohttp`."
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)
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app = create_app(adapter)
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runner = web.AppRunner(app, access_log=None)
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await runner.setup()
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site = web.TCPSite(runner, host=host, port=port)
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await site.start()
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logger.info(
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"proxy: listening on http://%s:%d/v1 -> %s",
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host, port, adapter.display_name,
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)
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stop_event = shutdown_event or asyncio.Event()
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# Wire signal handlers when we own the loop's lifetime.
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if shutdown_event is None:
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loop = asyncio.get_running_loop()
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for sig in (signal.SIGINT, signal.SIGTERM):
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try:
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loop.add_signal_handler(sig, stop_event.set) # windows-footgun: ok
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except NotImplementedError:
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# Windows / restricted environments — Ctrl+C will still
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# raise KeyboardInterrupt and unwind us.
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pass
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try:
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await stop_event.wait()
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finally:
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logger.info("proxy: shutting down")
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await runner.cleanup()
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__all__ = [
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"create_app",
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"run_server",
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"DEFAULT_HOST",
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"DEFAULT_PORT",
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"AIOHTTP_AVAILABLE",
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]
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