Class SharedMemoryManager

Lib/multiprocessing/managers.py:1376–1438

Like SyncManager but uses SharedMemoryServer instead of Server. It provides methods for creating and returning SharedMemory instances and for creating a list-like object (ShareableList) backed by shared memory. It also provides methods that create and return Proxy Objects

    class SharedMemoryManager(BaseManager):
        """Like SyncManager but uses SharedMemoryServer instead of Server.

        It provides methods for creating and returning SharedMemory instances
        and for creating a list-like object (ShareableList) backed by shared
        memory.  It also provides methods that create and return Proxy Objects
        that support synchronization across processes (i.e. multi-process-safe
        locks and semaphores).
        """

        _Server = SharedMemoryServer

        def __init__(self, *args, **kwargs):
            if os.name == "posix":
                # bpo-36867: Ensure the resource_tracker is running before
                # launching the manager process, so that concurrent
                # shared_memory manipulation both in the manager and in the
                # current process does not create two resource_tracker
                # processes.
                from . import resource_tracker
                resource_tracker.ensure_running()
            BaseManager.__init__(self, *args, **kwargs)
            util.debug(f"{self.__class__.__name__} created by pid {getpid()}")

        def __del__(self):
            util.debug(f"{self.__class__.__name__}.__del__ by pid {getpid()}")

        def get_server(self):
            'Better than monkeypatching for now; merge into Server ultimately'
            if self._state.value != State.INITIAL:
                if self._state.value == State.STARTED:
                    raise ProcessError("Already started SharedMemoryServer")
                elif self._state.value == State.SHUTDOWN:
                    raise ProcessError("SharedMemoryManager has shut down")
                else:
                    raise ProcessError(
                        "Unknown state {!r}".format(self._state.value))
            return self._Server(self._registry, self._address,
                                self._authkey, self._serializer)

        def SharedMemory(self, size):
            """Returns a new SharedMemory instance with the specified size in
            bytes, to be tracked by the manager."""
            with self._Client(self._address, authkey=self._authkey) as conn:
                sms = shared_memory.SharedMemory(None, create=True, size=size)
                try:
                    dispatch(conn, None, 'track_segment', (sms.name,))
                except BaseException as e:
                    sms.unlink()
                    raise e
            return sms

        def ShareableList(self, sequence):
            """Returns a new ShareableList instance populated with the values
            from the input sequence, to be tracked by the manager."""
            with self._Client(self._address, authkey=self._authkey) as conn:
                sl = shared_memory.ShareableList(sequence)
                try: