"""Python bindings for 0MQ.""" # Copyright (C) PyZMQ Developers # Distributed under the terms of the Modified BSD License. import atexit import os from threading import Lock from typing import Any, Dict, Generic, List, Optional, Type, TypeVar from warnings import warn from weakref import WeakSet from zmq.backend import Context as ContextBase from zmq.constants import ContextOption, Errno, SocketOption from zmq.error import ZMQError from .attrsettr import AttributeSetter, OptValT from .socket import Socket # notice when exiting, to avoid triggering term on exit _exiting = False def _notice_atexit() -> None: global _exiting _exiting = True atexit.register(_notice_atexit) T = TypeVar('T', bound='Context') ST = TypeVar('ST', bound='Socket', covariant=True) class Context(ContextBase, AttributeSetter, Generic[ST]): """Create a zmq Context A zmq Context creates sockets via its ``ctx.socket`` method. .. versionchanged:: 24 When using a Context as a context manager (``with zmq.Context()``), or deleting a context without closing it first, ``ctx.destroy()`` is called, closing any leftover sockets, instead of `ctx.term()` which requires sockets to be closed first. This prevents hangs caused by `ctx.term()` if sockets are left open, but means that unclean destruction of contexts (with sockets left open) is not safe if sockets are managed in other threads. """ sockopts: Dict[int, Any] _instance: Any = None _instance_lock = Lock() _instance_pid: Optional[int] = None _shadow = False _warn_destroy_close = False _sockets: WeakSet # mypy doesn't like a default value here _socket_class: Type[ST] = Socket # type: ignore def __init__(self: "Context[Socket]", io_threads: int = 1, **kwargs: Any) -> None: super().__init__(io_threads=io_threads, **kwargs) if kwargs.get('shadow', False): self._shadow = True else: self._shadow = False self.sockopts = {} self._sockets = WeakSet() def __del__(self) -> None: """Deleting a Context without closing it destroys it and all sockets. .. versionchanged:: 24 Switch from threadsafe `term()` which hangs in the event of open sockets to less safe `destroy()` which warns about any leftover sockets and closes them. """ # Calling locals() here conceals issue #1167 on Windows CPython 3.5.4. locals() if not self._shadow and not _exiting and not self.closed: self._warn_destroy_close = True if warn and getattr(self, "_sockets", None) is not None: # warn can be None during process teardown warn( f"Unclosed context {self}", ResourceWarning, stacklevel=2, source=self, ) self.destroy() _repr_cls = "zmq.Context" def __repr__(self) -> str: cls = self.__class__ # look up _repr_cls on exact class, not inherited _repr_cls = cls.__dict__.get("_repr_cls", None) if _repr_cls is None: _repr_cls = f"{cls.__module__}.{cls.__name__}" closed = ' closed' if self.closed else '' if getattr(self, "_sockets", None): n_sockets = len(self._sockets) s = 's' if n_sockets > 1 else '' sockets = f"{n_sockets} socket{s}" else: sockets = "" return f"<{_repr_cls}({sockets}) at {hex(id(self))}{closed}>" def __enter__(self: T) -> T: return self def __exit__(self, exc_type: Any, exc_value: Any, traceback: Any) -> None: # warn about any leftover sockets before closing them self._warn_destroy_close = True self.destroy() def __copy__(self: T, memo: Any = None) -> T: """Copying a Context creates a shadow copy""" return self.__class__.shadow(self.underlying) __deepcopy__ = __copy__ @classmethod def shadow(cls: Type[T], address: int) -> T: """Shadow an existing libzmq context address is the integer address of the libzmq context or an FFI pointer to it. .. versionadded:: 14.1 """ from zmq.utils.interop import cast_int_addr address = cast_int_addr(address) return cls(shadow=address) @classmethod def shadow_pyczmq(cls: Type[T], ctx: Any) -> T: """Shadow an existing pyczmq context ctx is the FFI `zctx_t *` pointer .. versionadded:: 14.1 """ from pyczmq import zctx # type: ignore from zmq.utils.interop import cast_int_addr underlying = zctx.underlying(ctx) address = cast_int_addr(underlying) return cls(shadow=address) # static method copied from tornado IOLoop.instance @classmethod def instance(cls: Type[T], io_threads: int = 1) -> T: """Returns a global Context instance. Most single-threaded applications have a single, global Context. Use this method instead of passing around Context instances throughout your code. A common pattern for classes that depend on Contexts is to use a default argument to enable programs with multiple Contexts but not require the argument for simpler applications:: class MyClass(object): def __init__(self, context=None): self.context = context or Context.instance() .. versionchanged:: 18.1 When called in a subprocess after forking, a new global instance is created instead of inheriting a Context that won't work from the parent process. """ if ( cls._instance is None or cls._instance_pid != os.getpid() or cls._instance.closed ): with cls._instance_lock: if ( cls._instance is None or cls._instance_pid != os.getpid() or cls._instance.closed ): cls._instance = cls(io_threads=io_threads) cls._instance_pid = os.getpid() return cls._instance def term(self) -> None: """Close or terminate the context. Context termination is performed in the following steps: - Any blocking operations currently in progress on sockets open within context shall raise :class:`zmq.ContextTerminated`. With the exception of socket.close(), any further operations on sockets open within this context shall raise :class:`zmq.ContextTerminated`. - After interrupting all blocking calls, term shall block until the following conditions are satisfied: - All sockets open within context have been closed. - For each socket within context, all messages sent on the socket have either been physically transferred to a network peer, or the socket's linger period set with the zmq.LINGER socket option has expired. For further details regarding socket linger behaviour refer to libzmq documentation for ZMQ_LINGER. This can be called to close the context by hand. If this is not called, the context will automatically be closed when it is garbage collected. """ super().term() # ------------------------------------------------------------------------- # Hooks for ctxopt completion # ------------------------------------------------------------------------- def __dir__(self) -> List[str]: keys = dir(self.__class__) keys.extend(ContextOption.__members__) return keys # ------------------------------------------------------------------------- # Creating Sockets # ------------------------------------------------------------------------- def _add_socket(self, socket: Any) -> None: """Add a weakref to a socket for Context.destroy / reference counting""" self._sockets.add(socket) def _rm_socket(self, socket: Any) -> None: """Remove a socket for Context.destroy / reference counting""" # allow _sockets to be None in case of process teardown if getattr(self, "_sockets", None) is not None: self._sockets.discard(socket) def destroy(self, linger: Optional[int] = None) -> None: """Close all sockets associated with this context and then terminate the context. .. warning:: destroy involves calling ``zmq_close()``, which is **NOT** threadsafe. If there are active sockets in other threads, this must not be called. Parameters ---------- linger : int, optional If specified, set LINGER on sockets prior to closing them. """ if self.closed: return sockets: List[ST] = list(getattr(self, "_sockets", None) or []) for s in sockets: if s and not s.closed: if self._warn_destroy_close and warn: # warn can be None during process teardown warn( f"Destroying context with unclosed socket {s}", ResourceWarning, stacklevel=3, source=s, ) if linger is not None: s.setsockopt(SocketOption.LINGER, linger) s.close() self.term() def socket(self: T, socket_type: int, **kwargs: Any) -> ST: """Create a Socket associated with this Context. Parameters ---------- socket_type : int The socket type, which can be any of the 0MQ socket types: REQ, REP, PUB, SUB, PAIR, DEALER, ROUTER, PULL, PUSH, etc. kwargs: will be passed to the __init__ method of the socket class. """ if self.closed: raise ZMQError(Errno.ENOTSUP) s: ST = self._socket_class( # set PYTHONTRACEMALLOC=2 to get the calling frame self, socket_type, **kwargs ) for opt, value in self.sockopts.items(): try: s.setsockopt(opt, value) except ZMQError: # ignore ZMQErrors, which are likely for socket options # that do not apply to a particular socket type, e.g. # SUBSCRIBE for non-SUB sockets. pass self._add_socket(s) return s def setsockopt(self, opt: int, value: Any) -> None: """set default socket options for new sockets created by this Context .. versionadded:: 13.0 """ self.sockopts[opt] = value def getsockopt(self, opt: int) -> OptValT: """get default socket options for new sockets created by this Context .. versionadded:: 13.0 """ return self.sockopts[opt] def _set_attr_opt(self, name: str, opt: int, value: OptValT) -> None: """set default sockopts as attributes""" if name in ContextOption.__members__: return self.set(opt, value) elif name in SocketOption.__members__: self.sockopts[opt] = value else: raise AttributeError(f"No such context or socket option: {name}") def _get_attr_opt(self, name: str, opt: int) -> OptValT: """get default sockopts as attributes""" if name in ContextOption.__members__: return self.get(opt) else: if opt not in self.sockopts: raise AttributeError(name) else: return self.sockopts[opt] def __delattr__(self, key: str) -> None: """delete default sockopts as attributes""" key = key.upper() try: opt = getattr(SocketOption, key) except AttributeError: raise AttributeError(f"No such socket option: {key!r}") else: if opt not in self.sockopts: raise AttributeError(key) else: del self.sockopts[opt] __all__ = ['Context']