refactor: connect-first stream lifecycle for sse and streamable_http (#2292)
Co-authored-by: Marcelo Trylesinski <marcelotryle@gmail.com>
This commit is contained in:
Max Isbey
GitHub
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commit
75a80b6f07
3 changed files with 161 additions and 153 deletions
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@ -57,108 +57,101 @@ async def sse_client(
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write_stream: MemoryObjectSendStream[SessionMessage]
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write_stream_reader: MemoryObjectReceiveStream[SessionMessage]
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read_stream_writer, read_stream = anyio.create_memory_object_stream(0)
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write_stream, write_stream_reader = anyio.create_memory_object_stream(0)
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logger.debug(f"Connecting to SSE endpoint: {remove_request_params(url)}")
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async with httpx_client_factory(
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headers=headers, auth=auth, timeout=httpx.Timeout(timeout, read=sse_read_timeout)
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) as client:
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async with aconnect_sse(client, "GET", url) as event_source:
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event_source.response.raise_for_status()
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logger.debug("SSE connection established")
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async with anyio.create_task_group() as tg:
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try:
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logger.debug(f"Connecting to SSE endpoint: {remove_request_params(url)}")
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async with httpx_client_factory(
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headers=headers, auth=auth, timeout=httpx.Timeout(timeout, read=sse_read_timeout)
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) as client:
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async with aconnect_sse(
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client,
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"GET",
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url,
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) as event_source:
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event_source.response.raise_for_status()
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logger.debug("SSE connection established")
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read_stream_writer, read_stream = anyio.create_memory_object_stream(0)
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write_stream, write_stream_reader = anyio.create_memory_object_stream(0)
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async def sse_reader(task_status: TaskStatus[str] = anyio.TASK_STATUS_IGNORED):
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try:
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async for sse in event_source.aiter_sse(): # pragma: no branch
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logger.debug(f"Received SSE event: {sse.event}")
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match sse.event:
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case "endpoint":
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endpoint_url = urljoin(url, sse.data)
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logger.debug(f"Received endpoint URL: {endpoint_url}")
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async def sse_reader(task_status: TaskStatus[str] = anyio.TASK_STATUS_IGNORED):
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try:
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async for sse in event_source.aiter_sse(): # pragma: no branch
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logger.debug(f"Received SSE event: {sse.event}")
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match sse.event:
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case "endpoint":
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endpoint_url = urljoin(url, sse.data)
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logger.debug(f"Received endpoint URL: {endpoint_url}")
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url_parsed = urlparse(url)
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endpoint_parsed = urlparse(endpoint_url)
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if ( # pragma: no cover
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url_parsed.netloc != endpoint_parsed.netloc
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or url_parsed.scheme != endpoint_parsed.scheme
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):
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error_msg = ( # pragma: no cover
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f"Endpoint origin does not match connection origin: {endpoint_url}"
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)
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logger.error(error_msg) # pragma: no cover
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raise ValueError(error_msg) # pragma: no cover
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if on_session_created:
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session_id = _extract_session_id_from_endpoint(endpoint_url)
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if session_id:
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on_session_created(session_id)
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task_status.started(endpoint_url)
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case "message":
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# Skip empty data (keep-alive pings)
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if not sse.data:
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continue
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try:
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message = types.jsonrpc_message_adapter.validate_json(
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sse.data, by_name=False
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)
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logger.debug(f"Received server message: {message}")
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except Exception as exc: # pragma: no cover
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logger.exception("Error parsing server message") # pragma: no cover
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await read_stream_writer.send(exc) # pragma: no cover
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continue # pragma: no cover
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session_message = SessionMessage(message)
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await read_stream_writer.send(session_message)
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case _: # pragma: no cover
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logger.warning(f"Unknown SSE event: {sse.event}") # pragma: no cover
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except SSEError as sse_exc: # pragma: lax no cover
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logger.exception("Encountered SSE exception")
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raise sse_exc
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except Exception as exc: # pragma: lax no cover
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logger.exception("Error in sse_reader")
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await read_stream_writer.send(exc)
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finally:
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await read_stream_writer.aclose()
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async def post_writer(endpoint_url: str):
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try:
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async with write_stream_reader:
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async for session_message in write_stream_reader:
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logger.debug(f"Sending client message: {session_message}")
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response = await client.post(
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endpoint_url,
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json=session_message.message.model_dump(
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by_alias=True,
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mode="json",
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exclude_unset=True,
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),
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url_parsed = urlparse(url)
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endpoint_parsed = urlparse(endpoint_url)
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if ( # pragma: no cover
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url_parsed.netloc != endpoint_parsed.netloc
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or url_parsed.scheme != endpoint_parsed.scheme
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):
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error_msg = ( # pragma: no cover
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f"Endpoint origin does not match connection origin: {endpoint_url}"
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)
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response.raise_for_status()
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logger.debug(f"Client message sent successfully: {response.status_code}")
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except Exception: # pragma: lax no cover
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logger.exception("Error in post_writer")
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finally:
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await write_stream.aclose()
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logger.error(error_msg) # pragma: no cover
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raise ValueError(error_msg) # pragma: no cover
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endpoint_url = await tg.start(sse_reader)
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logger.debug(f"Starting post writer with endpoint URL: {endpoint_url}")
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tg.start_soon(post_writer, endpoint_url)
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if on_session_created:
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session_id = _extract_session_id_from_endpoint(endpoint_url)
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if session_id:
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on_session_created(session_id)
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try:
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yield read_stream, write_stream
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finally:
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tg.cancel_scope.cancel()
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finally:
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await read_stream_writer.aclose()
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await write_stream.aclose()
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await read_stream.aclose()
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await write_stream_reader.aclose()
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task_status.started(endpoint_url)
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case "message":
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# Skip empty data (keep-alive pings)
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if not sse.data:
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continue
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try:
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message = types.jsonrpc_message_adapter.validate_json(sse.data, by_name=False)
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logger.debug(f"Received server message: {message}")
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except Exception as exc: # pragma: no cover
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logger.exception("Error parsing server message") # pragma: no cover
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await read_stream_writer.send(exc) # pragma: no cover
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continue # pragma: no cover
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session_message = SessionMessage(message)
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await read_stream_writer.send(session_message)
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case _: # pragma: no cover
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logger.warning(f"Unknown SSE event: {sse.event}") # pragma: no cover
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except SSEError as sse_exc: # pragma: lax no cover
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logger.exception("Encountered SSE exception")
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raise sse_exc
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except Exception as exc: # pragma: lax no cover
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logger.exception("Error in sse_reader")
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await read_stream_writer.send(exc)
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finally:
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await read_stream_writer.aclose()
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async def post_writer(endpoint_url: str):
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try:
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async with write_stream_reader, write_stream:
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async for session_message in write_stream_reader:
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logger.debug(f"Sending client message: {session_message}")
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response = await client.post(
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endpoint_url,
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json=session_message.message.model_dump(
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by_alias=True,
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mode="json",
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exclude_unset=True,
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),
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)
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response.raise_for_status()
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logger.debug(f"Client message sent successfully: {response.status_code}")
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except Exception: # pragma: lax no cover
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logger.exception("Error in post_writer")
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# On Python 3.14, coverage.py reports a phantom branch arc on this
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# line (->yield) when nested two async-with levels deep. The branch
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# is the unreachable "did __aexit__ suppress?" arm for memory streams.
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async with ( # pragma: no branch
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read_stream_writer,
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read_stream,
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write_stream,
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write_stream_reader,
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anyio.create_task_group() as tg,
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):
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endpoint_url = await tg.start(sse_reader)
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logger.debug(f"Starting post writer with endpoint URL: {endpoint_url}")
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tg.start_soon(post_writer, endpoint_url)
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yield read_stream, write_stream
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tg.cancel_scope.cancel()
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@ -440,7 +440,7 @@ class StreamableHTTPTransport:
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) -> None:
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"""Handle writing requests to the server."""
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try:
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async with write_stream_reader:
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async with write_stream_reader, read_stream_writer, write_stream:
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async for session_message in write_stream_reader:
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message = session_message.message
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metadata = (
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@ -480,9 +480,6 @@ class StreamableHTTPTransport:
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except Exception: # pragma: lax no cover
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logger.exception("Error in post_writer")
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finally:
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await read_stream_writer.aclose()
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await write_stream.aclose()
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async def terminate_session(self, client: httpx.AsyncClient) -> None:
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"""Terminate the session by sending a DELETE request."""
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@ -533,9 +530,6 @@ async def streamable_http_client(
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Example:
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See examples/snippets/clients/ for usage patterns.
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"""
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read_stream_writer, read_stream = anyio.create_memory_object_stream[SessionMessage | Exception](0)
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write_stream, write_stream_reader = anyio.create_memory_object_stream[SessionMessage](0)
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# Determine if we need to create and manage the client
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client_provided = http_client is not None
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client = http_client
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@ -546,36 +540,40 @@ async def streamable_http_client(
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transport = StreamableHTTPTransport(url)
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async with anyio.create_task_group() as tg:
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try:
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logger.debug(f"Connecting to StreamableHTTP endpoint: {url}")
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logger.debug(f"Connecting to StreamableHTTP endpoint: {url}")
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async with contextlib.AsyncExitStack() as stack:
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# Only manage client lifecycle if we created it
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if not client_provided:
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await stack.enter_async_context(client)
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async with contextlib.AsyncExitStack() as stack:
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# Only manage client lifecycle if we created it
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if not client_provided:
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await stack.enter_async_context(client)
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def start_get_stream() -> None:
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tg.start_soon(transport.handle_get_stream, client, read_stream_writer)
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read_stream_writer, read_stream = anyio.create_memory_object_stream[SessionMessage | Exception](0)
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write_stream, write_stream_reader = anyio.create_memory_object_stream[SessionMessage](0)
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tg.start_soon(
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transport.post_writer,
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client,
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write_stream_reader,
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read_stream_writer,
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write_stream,
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start_get_stream,
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tg,
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)
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async with (
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read_stream_writer,
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read_stream,
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write_stream,
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write_stream_reader,
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anyio.create_task_group() as tg,
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):
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try:
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yield read_stream, write_stream
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finally:
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if transport.session_id and terminate_on_close:
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await transport.terminate_session(client)
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tg.cancel_scope.cancel()
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finally:
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await read_stream_writer.aclose()
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await write_stream.aclose()
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await read_stream.aclose()
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await write_stream_reader.aclose()
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def start_get_stream() -> None:
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tg.start_soon(transport.handle_get_stream, client, read_stream_writer)
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tg.start_soon(
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transport.post_writer,
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client,
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write_stream_reader,
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read_stream_writer,
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write_stream,
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start_get_stream,
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tg,
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)
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try:
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yield read_stream, write_stream
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finally:
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if transport.session_id and terminate_on_close:
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await transport.terminate_session(client)
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tg.cancel_scope.cancel()
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@ -58,22 +58,39 @@ def _assert_no_memory_stream_leak() -> Iterator[None]:
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@pytest.mark.anyio
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async def test_sse_client_closes_all_streams_on_connection_error(free_tcp_port: int) -> None:
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"""sse_client must close all 4 stream ends when the connection fails.
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"""sse_client creates streams only after the SSE connection succeeds, so a
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ConnectError propagates directly with nothing to leak.
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Before the fix, only read_stream_writer and write_stream were closed in
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the finally block. read_stream and write_stream_reader were leaked.
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Before the fix, streams were created before connecting and only 2 of 4 were
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closed in the finally block.
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"""
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with _assert_no_memory_stream_leak():
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# sse_client enters a task group BEFORE connecting, so anyio wraps the
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# ConnectError from aconnect_sse in an ExceptionGroup.
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with pytest.raises(Exception) as exc_info: # noqa: B017
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with pytest.raises(httpx.ConnectError):
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async with sse_client(f"http://127.0.0.1:{free_tcp_port}/sse"):
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pytest.fail("should not reach here") # pragma: no cover
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assert exc_info.group_contains(httpx.ConnectError)
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# exc_info holds the traceback → holds frame locals → keeps leaked
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# streams alive. Must drop it before gc.collect() can detect a leak.
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del exc_info
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@pytest.mark.anyio
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async def test_sse_client_closes_all_streams_on_http_error() -> None:
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"""sse_client creates streams only after raise_for_status() passes, so an
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HTTPStatusError from a 4xx/5xx response propagates bare (not wrapped in an
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ExceptionGroup) with nothing to leak — the task group is never entered.
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"""
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def return_403(request: httpx.Request) -> httpx.Response:
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return httpx.Response(403)
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def mock_factory(
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headers: dict[str, str] | None = None,
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timeout: httpx.Timeout | None = None,
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auth: httpx.Auth | None = None,
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) -> httpx.AsyncClient:
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return httpx.AsyncClient(transport=httpx.MockTransport(return_403))
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with _assert_no_memory_stream_leak():
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with pytest.raises(httpx.HTTPStatusError):
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async with sse_client("http://test/sse", httpx_client_factory=mock_factory):
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pytest.fail("should not reach here") # pragma: no cover
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@pytest.mark.anyio
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