diff --git a/src/mcp/server/lowlevel/server.py b/src/mcp/server/lowlevel/server.py index efdf4b216e..6ca0eed3ab 100644 --- a/src/mcp/server/lowlevel/server.py +++ b/src/mcp/server/lowlevel/server.py @@ -77,6 +77,8 @@ async def main(): logger = logging.getLogger(__name__) +DEFAULT_READ_EOF_DRAIN_TIMEOUT_SECONDS = 1.0 + LifespanResultT = TypeVar("LifespanResultT", default=Any) _ParamsT = TypeVar("_ParamsT", bound=BaseModel, default=BaseModel) @@ -698,6 +700,18 @@ async def run( # but also make tracing exceptions much easier during testing and when using # in-process servers. raise_exceptions: bool = False, + # When True, the server is stateless and + # clients can perform initialization with any node. The client must still follow + # the initialization lifecycle, but can do so with any available node + # rather than requiring initialization for each connection. + stateless: bool = False, + # When True, treat read EOF as a half-close and allow in-flight handlers + # to drain their responses via the still-open write stream (e.g. stdio + # with bash-redirected stdin). + drain_on_read_close: bool = False, + # Maximum time to wait for in-flight handlers to drain after read EOF. + # None means wait indefinitely. + read_eof_drain_timeout_seconds: float | None = DEFAULT_READ_EOF_DRAIN_TIMEOUT_SECONDS, ) -> None: """Serve a single connection over the given streams until the read side closes. @@ -715,6 +729,9 @@ async def run( lifespan_state=lifespan_context, init_options=initialization_options, raise_exceptions=raise_exceptions, + session_id=None, + close_write_stream_on_read_close=not drain_on_read_close, + read_eof_drain_timeout_seconds=read_eof_drain_timeout_seconds, ) def streamable_http_app( diff --git a/src/mcp/server/mcpserver/server.py b/src/mcp/server/mcpserver/server.py index bc79c44a36..44901b7541 100644 --- a/src/mcp/server/mcpserver/server.py +++ b/src/mcp/server/mcpserver/server.py @@ -1022,6 +1022,7 @@ async def run_stdio_async(self) -> None: read_stream, write_stream, self._lowlevel_server.create_initialization_options(), + drain_on_read_close=True, ) async def run_sse_async( # pragma: no cover diff --git a/src/mcp/server/runner.py b/src/mcp/server/runner.py index 26e8efbe57..08c92b3ec8 100644 --- a/src/mcp/server/runner.py +++ b/src/mcp/server/runner.py @@ -476,6 +476,8 @@ async def serve_loop( session_id: str | None = None, init_options: InitializationOptions | None = None, raise_exceptions: bool = False, + close_write_stream_on_read_close: bool = True, + read_eof_drain_timeout_seconds: float | None = None, ) -> None: """Drive ``server`` in handshake-only loop mode over a stream pair until the channel closes. @@ -494,6 +496,8 @@ async def serve_loop( # next request (spec: SHOULD NOT, not MUST NOT) sees the initialized # state instead of failing the init-gate. inline_methods=frozenset({"initialize"}), + close_write_stream_on_read_close=close_write_stream_on_read_close, + read_eof_drain_timeout_seconds=read_eof_drain_timeout_seconds, ) connection = Connection.for_loop(dispatcher, session_id=session_id) await serve_connection( @@ -608,6 +612,8 @@ async def serve_dual_era_loop( session_id: str | None = None, init_options: InitializationOptions | None = None, raise_exceptions: bool = False, + close_write_stream_on_read_close: bool = True, + read_eof_drain_timeout_seconds: float | None = None, ) -> None: """Drive `server` over a duplex stream pair, in the era the client opens with. @@ -630,7 +636,13 @@ async def serve_dual_era_loop( ) if opens_modern: await _serve_modern_stream( - server, replayed, write_stream, lifespan_state=lifespan_state, raise_exceptions=raise_exceptions + server, + replayed, + write_stream, + lifespan_state=lifespan_state, + raise_exceptions=raise_exceptions, + close_write_stream_on_read_close=close_write_stream_on_read_close, + read_eof_drain_timeout_seconds=read_eof_drain_timeout_seconds, ) else: await _serve_legacy_stream( @@ -641,6 +653,8 @@ async def serve_dual_era_loop( session_id=session_id, init_options=init_options, raise_exceptions=raise_exceptions, + close_write_stream_on_read_close=close_write_stream_on_read_close, + read_eof_drain_timeout_seconds=read_eof_drain_timeout_seconds, ) finally: await write_stream.aclose() @@ -723,6 +737,8 @@ async def _serve_legacy_stream( session_id: str | None, init_options: InitializationOptions | None, raise_exceptions: bool, + close_write_stream_on_read_close: bool, + read_eof_drain_timeout_seconds: float | None, ) -> None: """Serve a 2025 handshake connection; enveloped requests are refused.""" dispatcher: JSONRPCDispatcher[TransportContext] = JSONRPCDispatcher( @@ -731,6 +747,8 @@ async def _serve_legacy_stream( raise_handler_exceptions=raise_exceptions, # `initialize` inline for the same pipelining reason as `serve_loop`. inline_methods=frozenset({"initialize"}), + close_write_stream_on_read_close=close_write_stream_on_read_close, + read_eof_drain_timeout_seconds=read_eof_drain_timeout_seconds, ) connection = Connection.for_loop(dispatcher, session_id=session_id) runner = ServerRunner(server, connection, lifespan_state, init_options=init_options) @@ -759,10 +777,16 @@ async def _serve_modern_stream( *, lifespan_state: LifespanT, raise_exceptions: bool, + close_write_stream_on_read_close: bool, + read_eof_drain_timeout_seconds: float | None, ) -> None: """Serve a 2026-07-28 connection: every request carries its own envelope.""" dispatcher: JSONRPCDispatcher[TransportContext] = JSONRPCDispatcher( - read_stream, write_stream, raise_handler_exceptions=raise_exceptions + read_stream, + write_stream, + raise_handler_exceptions=raise_exceptions, + close_write_stream_on_read_close=close_write_stream_on_read_close, + read_eof_drain_timeout_seconds=read_eof_drain_timeout_seconds, ) outbound = NotifyOnlyOutbound(dispatcher) diff --git a/src/mcp/shared/jsonrpc_dispatcher.py b/src/mcp/shared/jsonrpc_dispatcher.py index 87bdf31ceb..8092f0b4d1 100644 --- a/src/mcp/shared/jsonrpc_dispatcher.py +++ b/src/mcp/shared/jsonrpc_dispatcher.py @@ -10,6 +10,7 @@ import contextvars import logging from collections.abc import Awaitable, Callable, Mapping +from contextlib import AsyncExitStack from dataclasses import dataclass, field from functools import partial from typing import Any, Generic, Literal, cast @@ -272,6 +273,8 @@ def __init__( peer_cancel_mode: PeerCancelMode = "interrupt", raise_handler_exceptions: bool = False, inline_methods: frozenset[str] = frozenset(), + close_write_stream_on_read_close: bool = True, + read_eof_drain_timeout_seconds: float | None = None, on_stream_exception: Callable[[Exception], Awaitable[None]] | None = None, ) -> None: """Wire a dispatcher over a transport's `SessionMessage` stream pair. @@ -284,6 +287,13 @@ def __init__( inline_methods: Methods awaited in the read loop before the next message is dequeued (e.g. `initialize`); an inline handler that awaits the peer deadlocks the parked loop. + close_write_stream_on_read_close: Close the write stream when the + read stream closes. Full-duplex transports may set this to + false so in-flight handlers can finish writing responses after + input EOF. + read_eof_drain_timeout_seconds: Maximum time to wait for in-flight + handlers to drain after read EOF when the write stream stays + open; None waits indefinitely. on_stream_exception: Observer for `Exception` items on the read stream; without it they are debug-logged and dropped. Awaited inline in the read loop, so a slow observer stalls dispatch. @@ -298,6 +308,8 @@ def __init__( ) self._peer_cancel_mode: PeerCancelMode = peer_cancel_mode self._raise_handler_exceptions = raise_handler_exceptions + self._close_write_stream_on_read_close = close_write_stream_on_read_close + self._read_eof_drain_timeout_seconds = read_eof_drain_timeout_seconds self._inline_methods = inline_methods self.on_stream_exception = on_stream_exception """Observer for ``Exception`` items on the read stream. Mutable so a session can @@ -487,40 +499,50 @@ async def run( Single-shot: once the loop ends the dispatcher stays closed and cannot be restarted. """ self._on_notify_intercept = on_notify_intercept + normal_eof = False try: - # LIFO exits: the write stream closes only after the task-group join, so teardown writes still land. - async with self._write_stream: - async with anyio.create_task_group() as tg: - self._tg = tg - self._running = True - task_status.started() - try: - async with self._read_stream: - try: - async for item in self._read_stream: - # Duck-typed: only `ContextReceiveStream` carries the - # sender's per-message contextvars snapshot. - sender_ctx: contextvars.Context | None = getattr( - self._read_stream, "last_context", None - ) - await self._dispatch(item, on_request, on_notify, sender_ctx) - except anyio.ClosedResourceError: - # Receive end closed under us (stateless SHTTP teardown); same as EOF. - logger.debug("read stream closed by transport; treating as EOF") - # EOF: wake blocked `send_raw_request` waiters with CONNECTION_CLOSED. - self._running = False - self._closed = True - self._fan_out_closed() - finally: - # Cancel in-flight handlers; otherwise the task-group join - # waits on handlers whose callers are already gone. + async with anyio.create_task_group() as tg: + self._tg = tg + self._running = True + task_status.started() + try: + async with AsyncExitStack() as stack: + await stack.enter_async_context(self._read_stream) + if self._close_write_stream_on_read_close: + await stack.enter_async_context(self._write_stream) + try: + async for item in self._read_stream: + # Duck-typed: only `ContextReceiveStream` carries the + # sender's per-message contextvars snapshot. + sender_ctx: contextvars.Context | None = getattr( + self._read_stream, "last_context", None + ) + await self._dispatch(item, on_request, on_notify, sender_ctx) + except anyio.ClosedResourceError: + # Receive end closed under us (stateless SHTTP teardown); same as EOF. + logger.debug("read stream closed by transport; treating as EOF") + # EOF: wake blocked `send_raw_request` waiters with CONNECTION_CLOSED. + self._running = False + self._fan_out_closed() + normal_eof = True + finally: + if not normal_eof or self._close_write_stream_on_read_close: + # Cancel on crash/cancel paths. If read EOF also closed + # writes, handlers cannot drain responses anyway. tg.cancel_scope.cancel() + elif self._read_eof_drain_timeout_seconds is None: + pass + else: + tg.cancel_scope.deadline = anyio.current_time() + self._read_eof_drain_timeout_seconds finally: # Covers cancel/crash paths that skip the inline fan-out; idempotent. self._running = False self._closed = True self._tg = None self._fan_out_closed() + if not self._close_write_stream_on_read_close: + with anyio.CancelScope(shield=True): + await self._write_stream.aclose() await resync_tracer() async def _dispatch( diff --git a/tests/server/test_cancel_handling.py b/tests/server/test_cancel_handling.py index fd0e4b28af..1547ca9471 100644 --- a/tests/server/test_cancel_handling.py +++ b/tests/server/test_cancel_handling.py @@ -13,6 +13,7 @@ InitializeRequestParams, JSONRPCNotification, JSONRPCRequest, + JSONRPCResponse, ListToolsResult, PaginatedRequestParams, TextContent, @@ -107,17 +108,79 @@ async def first_request(): @pytest.mark.anyio -async def test_server_cancels_in_flight_handlers_on_transport_close(): - """When the transport closes mid-request, server.run() must cancel in-flight - handlers rather than join on them. +async def test_server_drains_in_flight_handlers_on_transport_read_eof(): + """When the transport's read side hits EOF (e.g., stdio stdin closes), the + server must drain already-started handlers so their responses reach the + peer via the still-open write side.""" + handler_started = anyio.Event() + handler_allowed_to_finish = anyio.Event() + server_run_returned = anyio.Event() - Without the cancel, the task group waits for the handler, which then tries - to respond through a write stream that _receive_loop already closed, - raising ClosedResourceError and crashing server.run() with exit code 1. + async def handle_call_tool(ctx: ServerRequestContext, params: CallToolRequestParams) -> CallToolResult: + handler_started.set() + await handler_allowed_to_finish.wait() + return CallToolResult(content=[TextContent(type="text", text="ok")]) - This drives server.run() with raw memory streams because InMemoryTransport - wraps it in its own finally-cancel (_memory.py) which masks the bug. - """ + server = Server("test", on_call_tool=handle_call_tool) + + to_server, server_read = anyio.create_memory_object_stream[SessionMessage | Exception](10) + server_write, from_server = anyio.create_memory_object_stream[SessionMessage](10) + + async def run_server(): + await server.run( + server_read, + server_write, + server.create_initialization_options(), + drain_on_read_close=True, + read_eof_drain_timeout_seconds=None, + ) + server_run_returned.set() + + init_req = JSONRPCRequest( + jsonrpc="2.0", + id=1, + method="initialize", + params=InitializeRequestParams( + protocol_version=LATEST_HANDSHAKE_VERSION, + capabilities=ClientCapabilities(), + client_info=Implementation(name="test", version="1.0"), + ).model_dump(by_alias=True, mode="json", exclude_none=True), + ) + initialized = JSONRPCNotification(jsonrpc="2.0", method="notifications/initialized") + call_req = JSONRPCRequest( + jsonrpc="2.0", + id=2, + method="tools/call", + params=CallToolRequestParams(name="slow", arguments={}).model_dump(by_alias=True, mode="json"), + ) + + with anyio.fail_after(5): + async with anyio.create_task_group() as tg, to_server, server_read, server_write, from_server: + tg.start_soon(run_server) + + await to_server.send(SessionMessage(init_req)) + await from_server.receive() # init response + await to_server.send(SessionMessage(initialized)) + await to_server.send(SessionMessage(call_req)) + + await handler_started.wait() + + # Close the server's input stream — this is what stdin EOF does. + # server.run()'s incoming_messages loop ends, finally-cancel fires, + # handler gets CancelledError, server.run() returns. + await to_server.aclose() + + handler_allowed_to_finish.set() + + response = await from_server.receive() + assert isinstance(response.message, JSONRPCResponse) + assert response.message.id == 2 + + await server_run_returned.wait() + + +@pytest.mark.anyio +async def test_server_bounds_drain_on_read_eof_when_handler_never_finishes(): handler_started = anyio.Event() handler_cancelled = anyio.Event() server_run_returned = anyio.Event() @@ -128,7 +191,6 @@ async def handle_call_tool(ctx: ServerRequestContext, params: CallToolRequestPar await anyio.sleep_forever() finally: handler_cancelled.set() - # unreachable: sleep_forever only exits via cancellation raise AssertionError # pragma: no cover server = Server("test", on_call_tool=handle_call_tool) @@ -136,6 +198,128 @@ async def handle_call_tool(ctx: ServerRequestContext, params: CallToolRequestPar to_server, server_read = anyio.create_memory_object_stream[SessionMessage | Exception](10) server_write, from_server = anyio.create_memory_object_stream[SessionMessage](10) + async def run_server(): + await server.run( + server_read, + server_write, + server.create_initialization_options(), + drain_on_read_close=True, + read_eof_drain_timeout_seconds=0.05, + ) + server_run_returned.set() + + init_req = JSONRPCRequest( + jsonrpc="2.0", + id=1, + method="initialize", + params=InitializeRequestParams( + protocol_version=LATEST_HANDSHAKE_VERSION, + capabilities=ClientCapabilities(), + client_info=Implementation(name="test", version="1.0"), + ).model_dump(by_alias=True, mode="json", exclude_none=True), + ) + initialized = JSONRPCNotification(jsonrpc="2.0", method="notifications/initialized") + call_req = JSONRPCRequest( + jsonrpc="2.0", + id=2, + method="tools/call", + params=CallToolRequestParams(name="slow", arguments={}).model_dump(by_alias=True, mode="json"), + ) + + with anyio.fail_after(2): + async with anyio.create_task_group() as tg, to_server, server_read, server_write, from_server: + tg.start_soon(run_server) + + await to_server.send(SessionMessage(init_req)) + await from_server.receive() # init response + await to_server.send(SessionMessage(initialized)) + await to_server.send(SessionMessage(call_req)) + + await handler_started.wait() + await to_server.aclose() + + await server_run_returned.wait() + + assert handler_cancelled.is_set() + + +@pytest.mark.anyio +async def test_server_reraises_handler_cancellation_when_server_is_cancelled(): + """If the server task is cancelled (e.g. KeyboardInterrupt), in-flight + request handlers will get cancelled too. Cancellation must be re-raised so + the task group can unwind cleanly.""" + handler_started = anyio.Event() + server_run_returned = anyio.Event() + cancel_scope = anyio.CancelScope() + + async def handle_call_tool(ctx: ServerRequestContext, params: CallToolRequestParams) -> CallToolResult: + handler_started.set() + await anyio.sleep_forever() + raise AssertionError # pragma: no cover + + server = Server("test", on_call_tool=handle_call_tool) + + to_server, server_read = anyio.create_memory_object_stream[SessionMessage | Exception](10) + server_write, from_server = anyio.create_memory_object_stream[SessionMessage](10) + + async def run_server(): + try: + with cancel_scope: + await server.run(server_read, server_write, server.create_initialization_options()) + finally: + server_run_returned.set() + + init_req = JSONRPCRequest( + jsonrpc="2.0", + id=1, + method="initialize", + params=InitializeRequestParams( + protocol_version=LATEST_HANDSHAKE_VERSION, + capabilities=ClientCapabilities(), + client_info=Implementation(name="test", version="1.0"), + ).model_dump(by_alias=True, mode="json", exclude_none=True), + ) + initialized = JSONRPCNotification(jsonrpc="2.0", method="notifications/initialized") + call_req = JSONRPCRequest( + jsonrpc="2.0", + id=2, + method="tools/call", + params=CallToolRequestParams(name="slow", arguments={}).model_dump(by_alias=True, mode="json"), + ) + + with anyio.fail_after(5): + async with anyio.create_task_group() as tg, to_server, server_read, server_write, from_server: + tg.start_soon(run_server) + + await to_server.send(SessionMessage(init_req)) + await from_server.receive() # init response + await to_server.send(SessionMessage(initialized)) + await to_server.send(SessionMessage(call_req)) + + await handler_started.wait() + cancel_scope.cancel() + await server_run_returned.wait() + + +@pytest.mark.anyio +async def test_server_drops_response_when_write_stream_closes_mid_request(): + """If the write side closes while a handler is in-flight, responding may + raise (ClosedResourceError/BrokenResourceError). The handler task should + exit without crashing the server.""" + handler_started = anyio.Event() + allow_finish = anyio.Event() + server_run_returned = anyio.Event() + + async def handle_call_tool(ctx: ServerRequestContext, params: CallToolRequestParams) -> CallToolResult: + handler_started.set() + await allow_finish.wait() + return CallToolResult(content=[TextContent(type="text", text="ok")]) + + server = Server("test", on_call_tool=handle_call_tool) + + to_server, server_read = anyio.create_memory_object_stream[SessionMessage | Exception](10) + server_write, from_server = anyio.create_memory_object_stream[SessionMessage](10) + async def run_server(): await server.run(server_read, server_write, server.create_initialization_options()) server_run_returned.set() @@ -168,16 +352,13 @@ async def run_server(): await to_server.send(SessionMessage(call_req)) await handler_started.wait() + await server_write.aclose() - # Close the server's input stream — this is what stdin EOF does. - # server.run()'s incoming_messages loop ends, finally-cancel fires, - # handler gets CancelledError, server.run() returns. + allow_finish.set() await to_server.aclose() await server_run_returned.wait() - assert handler_cancelled.is_set() - @pytest.mark.anyio async def test_server_handles_transport_close_with_pending_server_to_client_requests(): diff --git a/tests/server/test_stdio.py b/tests/server/test_stdio.py index eafd1fca59..b6268e0b2c 100644 --- a/tests/server/test_stdio.py +++ b/tests/server/test_stdio.py @@ -13,15 +13,27 @@ from mcp_types import ( CLIENT_CAPABILITIES_META_KEY, CLIENT_INFO_META_KEY, + LATEST_PROTOCOL_VERSION, PROTOCOL_VERSION_META_KEY, SERVER_INFO_META_KEY, + CallToolRequestParams, + CallToolResult, + ClientCapabilities, + Implementation, + InitializeRequestParams, JSONRPCMessage, + JSONRPCNotification, JSONRPCRequest, JSONRPCResponse, + ListToolsResult, + PaginatedRequestParams, + TextContent, + Tool, jsonrpc_message_adapter, ) from typing_extensions import Buffer +from mcp.server import Server, ServerRequestContext from mcp.server.mcpserver import MCPServer from mcp.server.stdio import stdio_server from mcp.shared.message import SessionMessage @@ -692,3 +704,87 @@ def test_mcpserver_run_stdio_serves_a_modern_connection(monkeypatch: pytest.Monk # resultType is modern-only: proves the request was served at the discovered version. assert responses[1].result["tools"] == [] assert responses[1].result["resultType"] == "complete" + + +@pytest.mark.anyio +async def test_stdio_server_drains_in_flight_responses_on_stdin_eof(): + """When stdin reaches EOF (e.g., bash-redirected input), already-received + requests must still be able to emit their responses on stdout.""" + stdin = io.StringIO() + stdout = io.StringIO() + + tool_started_count = 0 + both_tools_started = anyio.Event() + allow_tools_to_finish = anyio.Event() + + async def handle_list_tools(ctx: ServerRequestContext, params: PaginatedRequestParams | None) -> ListToolsResult: + return ListToolsResult(tools=[Tool(name="slow", description="test", input_schema={"type": "object"})]) + + async def handle_call_tool(ctx: ServerRequestContext, params: CallToolRequestParams) -> CallToolResult: + nonlocal tool_started_count + tool_started_count += 1 + if tool_started_count == 2: + both_tools_started.set() + await allow_tools_to_finish.wait() + return CallToolResult(content=[TextContent(type="text", text="ok")]) + + server = Server("test", on_list_tools=handle_list_tools, on_call_tool=handle_call_tool) + + init_req = JSONRPCRequest( + jsonrpc="2.0", + id=0, + method="initialize", + params=InitializeRequestParams( + protocol_version=LATEST_PROTOCOL_VERSION, + capabilities=ClientCapabilities(), + client_info=Implementation(name="test", version="1.0"), + ).model_dump(by_alias=True, mode="json", exclude_none=True), + ) + initialized = JSONRPCNotification(jsonrpc="2.0", method="notifications/initialized") + list_tools = JSONRPCRequest(jsonrpc="2.0", id=10, method="tools/list") + call_1 = JSONRPCRequest( + jsonrpc="2.0", + id=1, + method="tools/call", + params=CallToolRequestParams(name="slow", arguments={}).model_dump(by_alias=True, mode="json"), + ) + call_2 = JSONRPCRequest( + jsonrpc="2.0", + id=2, + method="tools/call", + params=CallToolRequestParams(name="slow", arguments={}).model_dump(by_alias=True, mode="json"), + ) + + for message in (init_req, initialized, list_tools, call_1, call_2): + stdin.write(message.model_dump_json(by_alias=True, exclude_none=True) + "\n") + stdin.seek(0) + + async with stdio_server(stdin=anyio.AsyncFile(stdin), stdout=anyio.AsyncFile(stdout)) as ( + read_stream, + write_stream, + ): + with anyio.fail_after(5): + async with anyio.create_task_group() as tg: # pragma: no branch + + async def run_server() -> None: + await server.run( + read_stream, + write_stream, + server.create_initialization_options(), + drain_on_read_close=True, + ) + + tg.start_soon(run_server) + await both_tools_started.wait() + allow_tools_to_finish.set() + + stdout.seek(0) + output_lines = [line.strip() for line in stdout.readlines()] + messages = [jsonrpc_message_adapter.validate_json(line) for line in output_lines] + ids: set[int | str] = set() + for message in messages: + assert isinstance(message, JSONRPCResponse) + ids.add(message.id) + + assert 1 in ids + assert 2 in ids diff --git a/tests/shared/test_jsonrpc_dispatcher.py b/tests/shared/test_jsonrpc_dispatcher.py index 9bee8b2c3b..7f06d3b825 100644 --- a/tests/shared/test_jsonrpc_dispatcher.py +++ b/tests/shared/test_jsonrpc_dispatcher.py @@ -369,6 +369,62 @@ async def drive() -> None: s2c_recv.close() +@pytest.mark.anyio +async def test_run_closes_write_stream_after_clean_eof_without_drain_timeout(): + c2s_send, c2s_recv = anyio.create_memory_object_stream[SessionMessage | Exception](32) + s2c_send, s2c_recv = anyio.create_memory_object_stream[SessionMessage | Exception](32) + server: JSONRPCDispatcher[TransportContext] = JSONRPCDispatcher( + c2s_recv, + s2c_send, + close_write_stream_on_read_close=False, + read_eof_drain_timeout_seconds=None, + ) + on_request, on_notify = echo_handlers(Recorder()) + + with anyio.fail_after(5): + async with anyio.create_task_group() as tg, c2s_send, c2s_recv, s2c_send, s2c_recv: + await tg.start(server.run, on_request, on_notify) + c2s_send.close() + with pytest.raises(anyio.EndOfStream): # pragma: no branch + await s2c_recv.receive() + + +@pytest.mark.anyio +async def test_run_drains_in_flight_handlers_on_clean_eof_without_timeout(): + c2s_send, c2s_recv = anyio.create_memory_object_stream[SessionMessage | Exception](32) + s2c_send, s2c_recv = anyio.create_memory_object_stream[SessionMessage | Exception](32) + server: JSONRPCDispatcher[TransportContext] = JSONRPCDispatcher( + c2s_recv, + s2c_send, + close_write_stream_on_read_close=False, + read_eof_drain_timeout_seconds=None, + ) + handler_started = anyio.Event() + handler_allowed_to_finish = anyio.Event() + + async def handle_request(ctx: DCtx, method: str, params: Mapping[str, Any] | None) -> dict[str, Any]: + handler_started.set() + await handler_allowed_to_finish.wait() + return {"drained": True} + + async def on_notify(ctx: DCtx, method: str, params: Mapping[str, Any] | None) -> None: + raise NotImplementedError + + with anyio.fail_after(5): + async with anyio.create_task_group() as tg, c2s_send, c2s_recv, s2c_send, s2c_recv: + await tg.start(server.run, handle_request, on_notify) + await c2s_send.send(SessionMessage(message=JSONRPCRequest(jsonrpc="2.0", id=1, method="x", params=None))) + await handler_started.wait() + c2s_send.close() + handler_allowed_to_finish.set() + + response = await s2c_recv.receive() + assert isinstance(response, SessionMessage) + assert isinstance(response.message, JSONRPCResponse) + assert response.message.id == 1 + assert response.message.result == {"drained": True} + + @pytest.mark.anyio async def test_run_closes_write_stream_on_exit(): """run() owns both streams; the write end is released once the EOF teardown completes.""" @@ -1042,10 +1098,14 @@ async def test_shutdown_error_response_write_is_bounded_when_the_transport_is_we ): """Cancelling the task group hosting run() completes even when the shutdown error write wedges: only `_SHUTDOWN_WRITE_TIMEOUT` releases the join (SDK-defined). A 0-buffer stream nobody reads - expresses the wedge: run() closes its write stream only after the join, so the send stays parked.""" + expresses the wedge: drain-mode run() closes its write stream only after the join, so the send stays parked.""" c2s_send, c2s_recv = anyio.create_memory_object_stream[SessionMessage | Exception](1) s2c_send, s2c_recv = anyio.create_memory_object_stream[SessionMessage | Exception](0) - server: JSONRPCDispatcher[TransportContext] = JSONRPCDispatcher(c2s_recv, s2c_send) + server: JSONRPCDispatcher[TransportContext] = JSONRPCDispatcher( + c2s_recv, + s2c_send, + close_write_stream_on_read_close=False, + ) handler_started = anyio.Event() async def park(ctx: DCtx, method: str, params: Mapping[str, Any] | None) -> dict[str, Any]: @@ -1076,10 +1136,15 @@ async def on_notify(ctx: DCtx, method: str, params: Mapping[str, Any] | None) -> @pytest.mark.anyio async def test_shutdown_answers_in_flight_request_with_connection_closed(): """Read-stream EOF answers a still-running request with CONNECTION_CLOSED (SDK-defined): - run() keeps the write stream open until the task-group join, so the shielded teardown write lands.""" + drain-mode run() keeps the write stream open until the task-group join, so the shielded teardown write lands.""" c2s_send, c2s_recv = anyio.create_memory_object_stream[SessionMessage | Exception](4) s2c_send, s2c_recv = anyio.create_memory_object_stream[SessionMessage | Exception](4) - server: JSONRPCDispatcher[TransportContext] = JSONRPCDispatcher(c2s_recv, s2c_send) + server: JSONRPCDispatcher[TransportContext] = JSONRPCDispatcher( + c2s_recv, + s2c_send, + close_write_stream_on_read_close=False, + read_eof_drain_timeout_seconds=0.05, + ) handler_started = anyio.Event() async def park(ctx: DCtx, method: str, params: Mapping[str, Any] | None) -> dict[str, Any]: