Files
hermes-agent/agent/bounded_response.py
T

80 lines
3.1 KiB
Python

"""Bounded reads of HTTP error response bodies.
On a non-OK *streaming* response Hermes reads the body for a diagnostic (only ever shown truncated to
a few hundred chars). A bare ``response.read()`` is unbounded two ways: arbitrarily large body
(memory) or a body that stalls forever (hang). ``read_streaming_error_body`` caps bytes and enforces a
hard wall-clock deadline; callers use the returned text instead of ``response.text`` (unbounded /
raises after a partial stream read). ``httpx.iter_bytes()`` blocks *inside* the socket read, so the
read runs on a daemon thread; on timeout we close the response (unblocking the read) and return the
partial bytes. Used by the streaming error-body sites: native Gemini, Gemini Cloud Code, Antigravity.
"""
from __future__ import annotations
import logging
import threading
from typing import List
import httpx
logger = logging.getLogger(__name__)
# Comfortably holds any real provider error envelope while rejecting pathological bodies.
DEFAULT_ERROR_BODY_MAX_BYTES = 64 * 1024
# Hard deadline for the whole read; past it the connection is closed and the partial bytes are kept.
DEFAULT_ERROR_BODY_TIMEOUT_S = 10.0
def read_streaming_error_body(
response: httpx.Response,
*,
max_bytes: int = DEFAULT_ERROR_BODY_MAX_BYTES,
timeout_s: float = DEFAULT_ERROR_BODY_TIMEOUT_S,
) -> str:
"""Read a non-OK streaming body with a byte cap and a hard deadline.
Returns UTF-8 text (errors replaced) truncated to ``max_bytes``. Never raises: transport errors,
stalls and oversize bodies yield best-effort partial text (or ""), so a read error can't mask the
original failure.
"""
chunks: List[bytes] = []
state = {"truncated": False}
done = threading.Event()
def _drain() -> None:
total = 0
try:
for chunk in response.iter_bytes():
if not chunk:
continue
remaining = max_bytes - total
if len(chunk) > remaining:
if remaining > 0:
chunks.append(chunk[:remaining])
state["truncated"] = True
break
chunks.append(chunk)
total += len(chunk)
except Exception as exc: # noqa: BLE001 - error path must not raise
logger.debug("bounded error-body read failed: %s", exc)
finally:
done.set()
threading.Thread(target=_drain, name="bounded-error-body-read", daemon=True).start()
if not done.wait(timeout=timeout_s):
logger.debug(
"bounded error-body read: hard timeout after %.1fs (%d bytes so far)",
timeout_s, sum(len(c) for c in chunks),
)
# Closing cancels any in-flight socket read so the worker unwinds. No join (daemon, may be blocked in C).
try:
response.close()
except Exception: # noqa: BLE001
pass
if state["truncated"]:
logger.debug(
"bounded error-body read: capped at %d bytes (max=%d)", sum(len(c) for c in chunks), max_bytes,
)
return b"".join(chunks).decode("utf-8", errors="replace")