1""" 2Generic Asynchronous Message-based Protocol Support 3 4This module provides a generic framework for sending and receiving 5messages over an asyncio stream. `AsyncProtocol` is an abstract class 6that implements the core mechanisms of a simple send/receive protocol, 7and is designed to be extended. 8 9In this package, it is used as the implementation for the `QMPClient` 10class. 11""" 12 13# It's all the docstrings ... ! It's long for a good reason ^_^; 14# pylint: disable=too-many-lines 15 16import asyncio 17from asyncio import StreamReader, StreamWriter 18from enum import Enum 19from functools import wraps 20import logging 21import socket 22from ssl import SSLContext 23from typing import ( 24 Any, 25 Awaitable, 26 Callable, 27 Generic, 28 List, 29 Optional, 30 Tuple, 31 TypeVar, 32 Union, 33 cast, 34) 35 36from .error import QMPError 37from .util import ( 38 bottom_half, 39 create_task, 40 exception_summary, 41 flush, 42 is_closing, 43 pretty_traceback, 44 upper_half, 45 wait_closed, 46) 47 48 49T = TypeVar('T') 50_U = TypeVar('_U') 51_TaskFN = Callable[[], Awaitable[None]] # aka ``async def func() -> None`` 52 53InternetAddrT = Tuple[str, int] 54UnixAddrT = str 55SocketAddrT = Union[UnixAddrT, InternetAddrT] 56 57 58class Runstate(Enum): 59 """Protocol session runstate.""" 60 61 #: Fully quiesced and disconnected. 62 IDLE = 0 63 #: In the process of connecting or establishing a session. 64 CONNECTING = 1 65 #: Fully connected and active session. 66 RUNNING = 2 67 #: In the process of disconnecting. 68 #: Runstate may be returned to `IDLE` by calling `disconnect()`. 69 DISCONNECTING = 3 70 71 72class ConnectError(QMPError): 73 """ 74 Raised when the initial connection process has failed. 75 76 This Exception always wraps a "root cause" exception that can be 77 interrogated for additional information. 78 79 :param error_message: Human-readable string describing the error. 80 :param exc: The root-cause exception. 81 """ 82 def __init__(self, error_message: str, exc: Exception): 83 super().__init__(error_message) 84 #: Human-readable error string 85 self.error_message: str = error_message 86 #: Wrapped root cause exception 87 self.exc: Exception = exc 88 89 def __str__(self) -> str: 90 cause = str(self.exc) 91 if not cause: 92 # If there's no error string, use the exception name. 93 cause = exception_summary(self.exc) 94 return f"{self.error_message}: {cause}" 95 96 97class StateError(QMPError): 98 """ 99 An API command (connect, execute, etc) was issued at an inappropriate time. 100 101 This error is raised when a command like 102 :py:meth:`~AsyncProtocol.connect()` is issued at an inappropriate 103 time. 104 105 :param error_message: Human-readable string describing the state violation. 106 :param state: The actual `Runstate` seen at the time of the violation. 107 :param required: The `Runstate` required to process this command. 108 """ 109 def __init__(self, error_message: str, 110 state: Runstate, required: Runstate): 111 super().__init__(error_message) 112 self.error_message = error_message 113 self.state = state 114 self.required = required 115 116 117F = TypeVar('F', bound=Callable[..., Any]) # pylint: disable=invalid-name 118 119 120# Don't Panic. 121def require(required_state: Runstate) -> Callable[[F], F]: 122 """ 123 Decorator: protect a method so it can only be run in a certain `Runstate`. 124 125 :param required_state: The `Runstate` required to invoke this method. 126 :raise StateError: When the required `Runstate` is not met. 127 """ 128 def _decorator(func: F) -> F: 129 # _decorator is the decorator that is built by calling the 130 # require() decorator factory; e.g.: 131 # 132 # @require(Runstate.IDLE) def foo(): ... 133 # will replace 'foo' with the result of '_decorator(foo)'. 134 135 @wraps(func) 136 def _wrapper(proto: 'AsyncProtocol[Any]', 137 *args: Any, **kwargs: Any) -> Any: 138 # _wrapper is the function that gets executed prior to the 139 # decorated method. 140 141 name = type(proto).__name__ 142 143 if proto.runstate != required_state: 144 if proto.runstate == Runstate.CONNECTING: 145 emsg = f"{name} is currently connecting." 146 elif proto.runstate == Runstate.DISCONNECTING: 147 emsg = (f"{name} is disconnecting." 148 " Call disconnect() to return to IDLE state.") 149 elif proto.runstate == Runstate.RUNNING: 150 emsg = f"{name} is already connected and running." 151 elif proto.runstate == Runstate.IDLE: 152 emsg = f"{name} is disconnected and idle." 153 else: 154 assert False 155 raise StateError(emsg, proto.runstate, required_state) 156 # No StateError, so call the wrapped method. 157 return func(proto, *args, **kwargs) 158 159 # Return the decorated method; 160 # Transforming Func to Decorated[Func]. 161 return cast(F, _wrapper) 162 163 # Return the decorator instance from the decorator factory. Phew! 164 return _decorator 165 166 167class AsyncProtocol(Generic[T]): 168 """ 169 AsyncProtocol implements a generic async message-based protocol. 170 171 This protocol assumes the basic unit of information transfer between 172 client and server is a "message", the details of which are left up 173 to the implementation. It assumes the sending and receiving of these 174 messages is full-duplex and not necessarily correlated; i.e. it 175 supports asynchronous inbound messages. 176 177 It is designed to be extended by a specific protocol which provides 178 the implementations for how to read and send messages. These must be 179 defined in `_do_recv()` and `_do_send()`, respectively. 180 181 Other callbacks have a default implementation, but are intended to be 182 either extended or overridden: 183 184 - `_establish_session`: 185 The base implementation starts the reader/writer tasks. 186 A protocol implementation can override this call, inserting 187 actions to be taken prior to starting the reader/writer tasks 188 before the super() call; actions needing to occur afterwards 189 can be written after the super() call. 190 - `_on_message`: 191 Actions to be performed when a message is received. 192 - `_cb_outbound`: 193 Logging/Filtering hook for all outbound messages. 194 - `_cb_inbound`: 195 Logging/Filtering hook for all inbound messages. 196 This hook runs *before* `_on_message()`. 197 198 :param name: 199 Name used for logging messages, if any. By default, messages 200 will log to 'qemu.qmp.protocol', but each individual connection 201 can be given its own logger by giving it a name; messages will 202 then log to 'qemu.qmp.protocol.${name}'. 203 """ 204 # pylint: disable=too-many-instance-attributes 205 206 #: Logger object for debugging messages from this connection. 207 logger = logging.getLogger(__name__) 208 209 # Maximum allowable size of read buffer 210 _limit = 64 * 1024 211 212 # ------------------------- 213 # Section: Public interface 214 # ------------------------- 215 216 def __init__(self, name: Optional[str] = None) -> None: 217 #: The nickname for this connection, if any. 218 self.name: Optional[str] = name 219 if self.name is not None: 220 self.logger = self.logger.getChild(self.name) 221 222 # stream I/O 223 self._reader: Optional[StreamReader] = None 224 self._writer: Optional[StreamWriter] = None 225 226 # Outbound Message queue 227 self._outgoing: asyncio.Queue[T] 228 229 # Special, long-running tasks: 230 self._reader_task: Optional[asyncio.Future[None]] = None 231 self._writer_task: Optional[asyncio.Future[None]] = None 232 233 # Aggregate of the above two tasks, used for Exception management. 234 self._bh_tasks: Optional[asyncio.Future[Tuple[None, None]]] = None 235 236 #: Disconnect task. The disconnect implementation runs in a task 237 #: so that asynchronous disconnects (initiated by the 238 #: reader/writer) are allowed to wait for the reader/writers to 239 #: exit. 240 self._dc_task: Optional[asyncio.Future[None]] = None 241 242 self._runstate = Runstate.IDLE 243 self._runstate_changed: Optional[asyncio.Event] = None 244 245 # Server state for start_server() and _incoming() 246 self._server: Optional[asyncio.AbstractServer] = None 247 self._accepted: Optional[asyncio.Event] = None 248 249 def __repr__(self) -> str: 250 cls_name = type(self).__name__ 251 tokens = [] 252 if self.name is not None: 253 tokens.append(f"name={self.name!r}") 254 tokens.append(f"runstate={self.runstate.name}") 255 return f"<{cls_name} {' '.join(tokens)}>" 256 257 @property # @upper_half 258 def runstate(self) -> Runstate: 259 """The current `Runstate` of the connection.""" 260 return self._runstate 261 262 @upper_half 263 async def runstate_changed(self) -> Runstate: 264 """ 265 Wait for the `runstate` to change, then return that runstate. 266 """ 267 await self._runstate_event.wait() 268 return self.runstate 269 270 @upper_half 271 @require(Runstate.IDLE) 272 async def start_server_and_accept( 273 self, address: SocketAddrT, 274 ssl: Optional[SSLContext] = None 275 ) -> None: 276 """ 277 Accept a connection and begin processing message queues. 278 279 If this call fails, `runstate` is guaranteed to be set back to `IDLE`. 280 This method is precisely equivalent to calling `start_server()` 281 followed by `accept()`. 282 283 :param address: 284 Address to listen on; UNIX socket path or TCP address/port. 285 :param ssl: SSL context to use, if any. 286 287 :raise StateError: When the `Runstate` is not `IDLE`. 288 :raise ConnectError: 289 When a connection or session cannot be established. 290 291 This exception will wrap a more concrete one. In most cases, 292 the wrapped exception will be `OSError` or `EOFError`. If a 293 protocol-level failure occurs while establishing a new 294 session, the wrapped error may also be an `QMPError`. 295 """ 296 await self.start_server(address, ssl) 297 await self.accept() 298 assert self.runstate == Runstate.RUNNING 299 300 @upper_half 301 @require(Runstate.IDLE) 302 async def start_server(self, address: SocketAddrT, 303 ssl: Optional[SSLContext] = None) -> None: 304 """ 305 Start listening for an incoming connection, but do not wait for a peer. 306 307 This method starts listening for an incoming connection, but 308 does not block waiting for a peer. This call will return 309 immediately after binding and listening on a socket. A later 310 call to `accept()` must be made in order to finalize the 311 incoming connection. 312 313 :param address: 314 Address to listen on; UNIX socket path or TCP address/port. 315 :param ssl: SSL context to use, if any. 316 317 :raise StateError: When the `Runstate` is not `IDLE`. 318 :raise ConnectError: 319 When the server could not start listening on this address. 320 321 This exception will wrap a more concrete one. In most cases, 322 the wrapped exception will be `OSError`. 323 """ 324 await self._session_guard( 325 self._do_start_server(address, ssl), 326 'Failed to establish connection') 327 assert self.runstate == Runstate.CONNECTING 328 329 @upper_half 330 @require(Runstate.CONNECTING) 331 async def accept(self) -> None: 332 """ 333 Accept an incoming connection and begin processing message queues. 334 335 If this call fails, `runstate` is guaranteed to be set back to `IDLE`. 336 337 :raise StateError: When the `Runstate` is not `CONNECTING`. 338 :raise QMPError: When `start_server()` was not called yet. 339 :raise ConnectError: 340 When a connection or session cannot be established. 341 342 This exception will wrap a more concrete one. In most cases, 343 the wrapped exception will be `OSError` or `EOFError`. If a 344 protocol-level failure occurs while establishing a new 345 session, the wrapped error may also be an `QMPError`. 346 """ 347 if self._accepted is None: 348 raise QMPError("Cannot call accept() before start_server().") 349 await self._session_guard( 350 self._do_accept(), 351 'Failed to establish connection') 352 await self._session_guard( 353 self._establish_session(), 354 'Failed to establish session') 355 assert self.runstate == Runstate.RUNNING 356 357 @upper_half 358 @require(Runstate.IDLE) 359 async def connect(self, address: Union[SocketAddrT, socket.socket], 360 ssl: Optional[SSLContext] = None) -> None: 361 """ 362 Connect to the server and begin processing message queues. 363 364 If this call fails, `runstate` is guaranteed to be set back to `IDLE`. 365 366 :param address: 367 Address to connect to; UNIX socket path or TCP address/port. 368 :param ssl: SSL context to use, if any. 369 370 :raise StateError: When the `Runstate` is not `IDLE`. 371 :raise ConnectError: 372 When a connection or session cannot be established. 373 374 This exception will wrap a more concrete one. In most cases, 375 the wrapped exception will be `OSError` or `EOFError`. If a 376 protocol-level failure occurs while establishing a new 377 session, the wrapped error may also be an `QMPError`. 378 """ 379 await self._session_guard( 380 self._do_connect(address, ssl), 381 'Failed to establish connection') 382 await self._session_guard( 383 self._establish_session(), 384 'Failed to establish session') 385 assert self.runstate == Runstate.RUNNING 386 387 @upper_half 388 async def disconnect(self) -> None: 389 """ 390 Disconnect and wait for all tasks to fully stop. 391 392 If there was an exception that caused the reader/writers to 393 terminate prematurely, it will be raised here. 394 395 :raise Exception: When the reader or writer terminate unexpectedly. 396 """ 397 self.logger.debug("disconnect() called.") 398 self._schedule_disconnect() 399 await self._wait_disconnect() 400 401 # -------------------------- 402 # Section: Session machinery 403 # -------------------------- 404 405 async def _session_guard(self, coro: Awaitable[None], emsg: str) -> None: 406 """ 407 Async guard function used to roll back to `IDLE` on any error. 408 409 On any Exception, the state machine will be reset back to 410 `IDLE`. Most Exceptions will be wrapped with `ConnectError`, but 411 `BaseException` events will be left alone (This includes 412 asyncio.CancelledError, even prior to Python 3.8). 413 414 :param error_message: 415 Human-readable string describing what connection phase failed. 416 417 :raise BaseException: 418 When `BaseException` occurs in the guarded block. 419 :raise ConnectError: 420 When any other error is encountered in the guarded block. 421 """ 422 # Note: After Python 3.6 support is removed, this should be an 423 # @asynccontextmanager instead of accepting a callback. 424 try: 425 await coro 426 except BaseException as err: 427 self.logger.error("%s: %s", emsg, exception_summary(err)) 428 self.logger.debug("%s:\n%s\n", emsg, pretty_traceback()) 429 try: 430 # Reset the runstate back to IDLE. 431 await self.disconnect() 432 except: 433 # We don't expect any Exceptions from the disconnect function 434 # here, because we failed to connect in the first place. 435 # The disconnect() function is intended to perform 436 # only cannot-fail cleanup here, but you never know. 437 emsg = ( 438 "Unexpected bottom half exception. " 439 "This is a bug in the QMP library. " 440 "Please report it to <qemu-devel@nongnu.org> and " 441 "CC: John Snow <jsnow@redhat.com>." 442 ) 443 self.logger.critical("%s:\n%s\n", emsg, pretty_traceback()) 444 raise 445 446 # CancelledError is an Exception with special semantic meaning; 447 # We do NOT want to wrap it up under ConnectError. 448 # NB: CancelledError is not a BaseException before Python 3.8 449 if isinstance(err, asyncio.CancelledError): 450 raise 451 452 # Any other kind of error can be treated as some kind of connection 453 # failure broadly. Inspect the 'exc' field to explore the root 454 # cause in greater detail. 455 if isinstance(err, Exception): 456 raise ConnectError(emsg, err) from err 457 458 # Raise BaseExceptions un-wrapped, they're more important. 459 raise 460 461 @property 462 def _runstate_event(self) -> asyncio.Event: 463 # asyncio.Event() objects should not be created prior to entrance into 464 # an event loop, so we can ensure we create it in the correct context. 465 # Create it on-demand *only* at the behest of an 'async def' method. 466 if not self._runstate_changed: 467 self._runstate_changed = asyncio.Event() 468 return self._runstate_changed 469 470 @upper_half 471 @bottom_half 472 def _set_state(self, state: Runstate) -> None: 473 """ 474 Change the `Runstate` of the protocol connection. 475 476 Signals the `runstate_changed` event. 477 """ 478 if state == self._runstate: 479 return 480 481 self.logger.debug("Transitioning from '%s' to '%s'.", 482 str(self._runstate), str(state)) 483 self._runstate = state 484 self._runstate_event.set() 485 self._runstate_event.clear() 486 487 @bottom_half 488 async def _stop_server(self) -> None: 489 """ 490 Stop listening for / accepting new incoming connections. 491 """ 492 if self._server is None: 493 return 494 495 try: 496 self.logger.debug("Stopping server.") 497 self._server.close() 498 self.logger.debug("Server stopped.") 499 finally: 500 self._server = None 501 502 @bottom_half # However, it does not run from the R/W tasks. 503 async def _incoming(self, 504 reader: asyncio.StreamReader, 505 writer: asyncio.StreamWriter) -> None: 506 """ 507 Accept an incoming connection and signal the upper_half. 508 509 This method does the minimum necessary to accept a single 510 incoming connection. It signals back to the upper_half ASAP so 511 that any errors during session initialization can occur 512 naturally in the caller's stack. 513 514 :param reader: Incoming `asyncio.StreamReader` 515 :param writer: Incoming `asyncio.StreamWriter` 516 """ 517 peer = writer.get_extra_info('peername', 'Unknown peer') 518 self.logger.debug("Incoming connection from %s", peer) 519 520 if self._reader or self._writer: 521 # Sadly, we can have more than one pending connection 522 # because of https://bugs.python.org/issue46715 523 # Close any extra connections we don't actually want. 524 self.logger.warning("Extraneous connection inadvertently accepted") 525 writer.close() 526 return 527 528 # A connection has been accepted; stop listening for new ones. 529 assert self._accepted is not None 530 await self._stop_server() 531 self._reader, self._writer = (reader, writer) 532 self._accepted.set() 533 534 @upper_half 535 async def _do_start_server(self, address: SocketAddrT, 536 ssl: Optional[SSLContext] = None) -> None: 537 """ 538 Start listening for an incoming connection, but do not wait for a peer. 539 540 This method starts listening for an incoming connection, but does not 541 block waiting for a peer. This call will return immediately after 542 binding and listening to a socket. A later call to accept() must be 543 made in order to finalize the incoming connection. 544 545 :param address: 546 Address to listen on; UNIX socket path or TCP address/port. 547 :param ssl: SSL context to use, if any. 548 549 :raise OSError: For stream-related errors. 550 """ 551 assert self.runstate == Runstate.IDLE 552 self._set_state(Runstate.CONNECTING) 553 554 self.logger.debug("Awaiting connection on %s ...", address) 555 self._accepted = asyncio.Event() 556 557 if isinstance(address, tuple): 558 coro = asyncio.start_server( 559 self._incoming, 560 host=address[0], 561 port=address[1], 562 ssl=ssl, 563 backlog=1, 564 limit=self._limit, 565 ) 566 else: 567 coro = asyncio.start_unix_server( 568 self._incoming, 569 path=address, 570 ssl=ssl, 571 backlog=1, 572 limit=self._limit, 573 ) 574 575 # Allow runstate watchers to witness 'CONNECTING' state; some 576 # failures in the streaming layer are synchronous and will not 577 # otherwise yield. 578 await asyncio.sleep(0) 579 580 # This will start the server (bind(2), listen(2)). It will also 581 # call accept(2) if we yield, but we don't block on that here. 582 self._server = await coro 583 self.logger.debug("Server listening on %s", address) 584 585 @upper_half 586 async def _do_accept(self) -> None: 587 """ 588 Wait for and accept an incoming connection. 589 590 Requires that we have not yet accepted an incoming connection 591 from the upper_half, but it's OK if the server is no longer 592 running because the bottom_half has already accepted the 593 connection. 594 """ 595 assert self._accepted is not None 596 await self._accepted.wait() 597 assert self._server is None 598 self._accepted = None 599 600 self.logger.debug("Connection accepted.") 601 602 @upper_half 603 async def _do_connect(self, address: Union[SocketAddrT, socket.socket], 604 ssl: Optional[SSLContext] = None) -> None: 605 """ 606 Acting as the transport client, initiate a connection to a server. 607 608 :param address: 609 Address to connect to; UNIX socket path or TCP address/port. 610 :param ssl: SSL context to use, if any. 611 612 :raise OSError: For stream-related errors. 613 """ 614 assert self.runstate == Runstate.IDLE 615 self._set_state(Runstate.CONNECTING) 616 617 # Allow runstate watchers to witness 'CONNECTING' state; some 618 # failures in the streaming layer are synchronous and will not 619 # otherwise yield. 620 await asyncio.sleep(0) 621 622 if isinstance(address, socket.socket): 623 self.logger.debug("Connecting with existing socket: " 624 "fd=%d, family=%r, type=%r", 625 address.fileno(), address.family, address.type) 626 connect = asyncio.open_connection( 627 limit=self._limit, 628 ssl=ssl, 629 sock=address, 630 ) 631 elif isinstance(address, tuple): 632 self.logger.debug("Connecting to %s ...", address) 633 connect = asyncio.open_connection( 634 address[0], 635 address[1], 636 ssl=ssl, 637 limit=self._limit, 638 ) 639 else: 640 self.logger.debug("Connecting to file://%s ...", address) 641 connect = asyncio.open_unix_connection( 642 path=address, 643 ssl=ssl, 644 limit=self._limit, 645 ) 646 647 self._reader, self._writer = await connect 648 self.logger.debug("Connected.") 649 650 @upper_half 651 async def _establish_session(self) -> None: 652 """ 653 Establish a new session. 654 655 Starts the readers/writer tasks; subclasses may perform their 656 own negotiations here. The Runstate will be RUNNING upon 657 successful conclusion. 658 """ 659 assert self.runstate == Runstate.CONNECTING 660 661 self._outgoing = asyncio.Queue() 662 663 reader_coro = self._bh_loop_forever(self._bh_recv_message, 'Reader') 664 writer_coro = self._bh_loop_forever(self._bh_send_message, 'Writer') 665 666 self._reader_task = create_task(reader_coro) 667 self._writer_task = create_task(writer_coro) 668 669 self._bh_tasks = asyncio.gather( 670 self._reader_task, 671 self._writer_task, 672 ) 673 674 self._set_state(Runstate.RUNNING) 675 await asyncio.sleep(0) # Allow runstate_event to process 676 677 @upper_half 678 @bottom_half 679 def _schedule_disconnect(self) -> None: 680 """ 681 Initiate a disconnect; idempotent. 682 683 This method is used both in the upper-half as a direct 684 consequence of `disconnect()`, and in the bottom-half in the 685 case of unhandled exceptions in the reader/writer tasks. 686 687 It can be invoked no matter what the `runstate` is. 688 """ 689 if not self._dc_task: 690 self._set_state(Runstate.DISCONNECTING) 691 self.logger.debug("Scheduling disconnect.") 692 self._dc_task = create_task(self._bh_disconnect()) 693 694 @upper_half 695 async def _wait_disconnect(self) -> None: 696 """ 697 Waits for a previously scheduled disconnect to finish. 698 699 This method will gather any bottom half exceptions and re-raise 700 the one that occurred first; presuming it to be the root cause 701 of any subsequent Exceptions. It is intended to be used in the 702 upper half of the call chain. 703 704 :raise Exception: 705 Arbitrary exception re-raised on behalf of the reader/writer. 706 """ 707 assert self.runstate == Runstate.DISCONNECTING 708 assert self._dc_task 709 710 aws: List[Awaitable[object]] = [self._dc_task] 711 if self._bh_tasks: 712 aws.insert(0, self._bh_tasks) 713 all_defined_tasks = asyncio.gather(*aws) 714 715 # Ensure disconnect is done; Exception (if any) is not raised here: 716 await asyncio.wait((self._dc_task,)) 717 718 try: 719 await all_defined_tasks # Raise Exceptions from the bottom half. 720 finally: 721 self._cleanup() 722 self._set_state(Runstate.IDLE) 723 724 @upper_half 725 def _cleanup(self) -> None: 726 """ 727 Fully reset this object to a clean state and return to `IDLE`. 728 """ 729 def _paranoid_task_erase(task: Optional['asyncio.Future[_U]'] 730 ) -> Optional['asyncio.Future[_U]']: 731 # Help to erase a task, ENSURING it is fully quiesced first. 732 assert (task is None) or task.done() 733 return None if (task and task.done()) else task 734 735 assert self.runstate == Runstate.DISCONNECTING 736 self._dc_task = _paranoid_task_erase(self._dc_task) 737 self._reader_task = _paranoid_task_erase(self._reader_task) 738 self._writer_task = _paranoid_task_erase(self._writer_task) 739 self._bh_tasks = _paranoid_task_erase(self._bh_tasks) 740 741 self._reader = None 742 self._writer = None 743 self._accepted = None 744 745 # NB: _runstate_changed cannot be cleared because we still need it to 746 # send the final runstate changed event ...! 747 748 # ---------------------------- 749 # Section: Bottom Half methods 750 # ---------------------------- 751 752 @bottom_half 753 async def _bh_disconnect(self) -> None: 754 """ 755 Disconnect and cancel all outstanding tasks. 756 757 It is designed to be called from its task context, 758 :py:obj:`~AsyncProtocol._dc_task`. By running in its own task, 759 it is free to wait on any pending actions that may still need to 760 occur in either the reader or writer tasks. 761 """ 762 assert self.runstate == Runstate.DISCONNECTING 763 764 def _done(task: Optional['asyncio.Future[Any]']) -> bool: 765 return task is not None and task.done() 766 767 # If the server is running, stop it. 768 await self._stop_server() 769 770 # Are we already in an error pathway? If either of the tasks are 771 # already done, or if we have no tasks but a reader/writer; we 772 # must be. 773 # 774 # NB: We can't use _bh_tasks to check for premature task 775 # completion, because it may not yet have had a chance to run 776 # and gather itself. 777 tasks = tuple(filter(None, (self._writer_task, self._reader_task))) 778 error_pathway = _done(self._reader_task) or _done(self._writer_task) 779 if not tasks: 780 error_pathway |= bool(self._reader) or bool(self._writer) 781 782 try: 783 # Try to flush the writer, if possible. 784 # This *may* cause an error and force us over into the error path. 785 if not error_pathway: 786 await self._bh_flush_writer() 787 except BaseException as err: 788 error_pathway = True 789 emsg = "Failed to flush the writer" 790 self.logger.error("%s: %s", emsg, exception_summary(err)) 791 self.logger.debug("%s:\n%s\n", emsg, pretty_traceback()) 792 raise 793 finally: 794 # Cancel any still-running tasks (Won't raise): 795 if self._writer_task is not None and not self._writer_task.done(): 796 self.logger.debug("Cancelling writer task.") 797 self._writer_task.cancel() 798 if self._reader_task is not None and not self._reader_task.done(): 799 self.logger.debug("Cancelling reader task.") 800 self._reader_task.cancel() 801 802 # Close out the tasks entirely (Won't raise): 803 if tasks: 804 self.logger.debug("Waiting for tasks to complete ...") 805 await asyncio.wait(tasks) 806 807 # Lastly, close the stream itself. (*May raise*!): 808 await self._bh_close_stream(error_pathway) 809 self.logger.debug("Disconnected.") 810 811 @bottom_half 812 async def _bh_flush_writer(self) -> None: 813 if not self._writer_task: 814 return 815 816 self.logger.debug("Draining the outbound queue ...") 817 await self._outgoing.join() 818 if self._writer is not None: 819 self.logger.debug("Flushing the StreamWriter ...") 820 await flush(self._writer) 821 822 @bottom_half 823 async def _bh_close_stream(self, error_pathway: bool = False) -> None: 824 # NB: Closing the writer also implicitly closes the reader. 825 if not self._writer: 826 return 827 828 if not is_closing(self._writer): 829 self.logger.debug("Closing StreamWriter.") 830 self._writer.close() 831 832 self.logger.debug("Waiting for StreamWriter to close ...") 833 try: 834 await wait_closed(self._writer) 835 except Exception: # pylint: disable=broad-except 836 # It's hard to tell if the Stream is already closed or 837 # not. Even if one of the tasks has failed, it may have 838 # failed for a higher-layered protocol reason. The 839 # stream could still be open and perfectly fine. 840 # I don't know how to discern its health here. 841 842 if error_pathway: 843 # We already know that *something* went wrong. Let's 844 # just trust that the Exception we already have is the 845 # better one to present to the user, even if we don't 846 # genuinely *know* the relationship between the two. 847 self.logger.debug( 848 "Discarding Exception from wait_closed:\n%s\n", 849 pretty_traceback(), 850 ) 851 else: 852 # Oops, this is a brand-new error! 853 raise 854 finally: 855 self.logger.debug("StreamWriter closed.") 856 857 @bottom_half 858 async def _bh_loop_forever(self, async_fn: _TaskFN, name: str) -> None: 859 """ 860 Run one of the bottom-half methods in a loop forever. 861 862 If the bottom half ever raises any exception, schedule a 863 disconnect that will terminate the entire loop. 864 865 :param async_fn: The bottom-half method to run in a loop. 866 :param name: The name of this task, used for logging. 867 """ 868 try: 869 while True: 870 await async_fn() 871 except asyncio.CancelledError: 872 # We have been cancelled by _bh_disconnect, exit gracefully. 873 self.logger.debug("Task.%s: cancelled.", name) 874 return 875 except BaseException as err: 876 self.logger.log( 877 logging.INFO if isinstance(err, EOFError) else logging.ERROR, 878 "Task.%s: %s", 879 name, exception_summary(err) 880 ) 881 self.logger.debug("Task.%s: failure:\n%s\n", 882 name, pretty_traceback()) 883 self._schedule_disconnect() 884 raise 885 finally: 886 self.logger.debug("Task.%s: exiting.", name) 887 888 @bottom_half 889 async def _bh_send_message(self) -> None: 890 """ 891 Wait for an outgoing message, then send it. 892 893 Designed to be run in `_bh_loop_forever()`. 894 """ 895 msg = await self._outgoing.get() 896 try: 897 await self._send(msg) 898 finally: 899 self._outgoing.task_done() 900 901 @bottom_half 902 async def _bh_recv_message(self) -> None: 903 """ 904 Wait for an incoming message and call `_on_message` to route it. 905 906 Designed to be run in `_bh_loop_forever()`. 907 """ 908 msg = await self._recv() 909 await self._on_message(msg) 910 911 # -------------------- 912 # Section: Message I/O 913 # -------------------- 914 915 @upper_half 916 @bottom_half 917 def _cb_outbound(self, msg: T) -> T: 918 """ 919 Callback: outbound message hook. 920 921 This is intended for subclasses to be able to add arbitrary 922 hooks to filter or manipulate outgoing messages. The base 923 implementation does nothing but log the message without any 924 manipulation of the message. 925 926 :param msg: raw outbound message 927 :return: final outbound message 928 """ 929 self.logger.debug("--> %s", str(msg)) 930 return msg 931 932 @upper_half 933 @bottom_half 934 def _cb_inbound(self, msg: T) -> T: 935 """ 936 Callback: inbound message hook. 937 938 This is intended for subclasses to be able to add arbitrary 939 hooks to filter or manipulate incoming messages. The base 940 implementation does nothing but log the message without any 941 manipulation of the message. 942 943 This method does not "handle" incoming messages; it is a filter. 944 The actual "endpoint" for incoming messages is `_on_message()`. 945 946 :param msg: raw inbound message 947 :return: processed inbound message 948 """ 949 self.logger.debug("<-- %s", str(msg)) 950 return msg 951 952 @upper_half 953 @bottom_half 954 async def _readline(self) -> bytes: 955 """ 956 Wait for a newline from the incoming reader. 957 958 This method is provided as a convenience for upper-layer 959 protocols, as many are line-based. 960 961 This method *may* return a sequence of bytes without a trailing 962 newline if EOF occurs, but *some* bytes were received. In this 963 case, the next call will raise `EOFError`. It is assumed that 964 the layer 5 protocol will decide if there is anything meaningful 965 to be done with a partial message. 966 967 :raise OSError: For stream-related errors. 968 :raise EOFError: 969 If the reader stream is at EOF and there are no bytes to return. 970 :return: bytes, including the newline. 971 """ 972 assert self._reader is not None 973 msg_bytes = await self._reader.readline() 974 975 if not msg_bytes: 976 if self._reader.at_eof(): 977 raise EOFError 978 979 return msg_bytes 980 981 @upper_half 982 @bottom_half 983 async def _do_recv(self) -> T: 984 """ 985 Abstract: Read from the stream and return a message. 986 987 Very low-level; intended to only be called by `_recv()`. 988 """ 989 raise NotImplementedError 990 991 @upper_half 992 @bottom_half 993 async def _recv(self) -> T: 994 """ 995 Read an arbitrary protocol message. 996 997 .. warning:: 998 This method is intended primarily for `_bh_recv_message()` 999 to use in an asynchronous task loop. Using it outside of 1000 this loop will "steal" messages from the normal routing 1001 mechanism. It is safe to use prior to `_establish_session()`, 1002 but should not be used otherwise. 1003 1004 This method uses `_do_recv()` to retrieve the raw message, and 1005 then transforms it using `_cb_inbound()`. 1006 1007 :return: A single (filtered, processed) protocol message. 1008 """ 1009 message = await self._do_recv() 1010 return self._cb_inbound(message) 1011 1012 @upper_half 1013 @bottom_half 1014 def _do_send(self, msg: T) -> None: 1015 """ 1016 Abstract: Write a message to the stream. 1017 1018 Very low-level; intended to only be called by `_send()`. 1019 """ 1020 raise NotImplementedError 1021 1022 @upper_half 1023 @bottom_half 1024 async def _send(self, msg: T) -> None: 1025 """ 1026 Send an arbitrary protocol message. 1027 1028 This method will transform any outgoing messages according to 1029 `_cb_outbound()`. 1030 1031 .. warning:: 1032 Like `_recv()`, this method is intended to be called by 1033 the writer task loop that processes outgoing 1034 messages. Calling it directly may circumvent logic 1035 implemented by the caller meant to correlate outgoing and 1036 incoming messages. 1037 1038 :raise OSError: For problems with the underlying stream. 1039 """ 1040 msg = self._cb_outbound(msg) 1041 self._do_send(msg) 1042 1043 @bottom_half 1044 async def _on_message(self, msg: T) -> None: 1045 """ 1046 Called to handle the receipt of a new message. 1047 1048 .. caution:: 1049 This is executed from within the reader loop, so be advised 1050 that waiting on either the reader or writer task will lead 1051 to deadlock. Additionally, any unhandled exceptions will 1052 directly cause the loop to halt, so logic may be best-kept 1053 to a minimum if at all possible. 1054 1055 :param msg: The incoming message, already logged/filtered. 1056 """ 1057 # Nothing to do in the abstract case. 1058