# Source code for distributed.core

    from __future__ import annotations

    import asyncio
    import functools
    import inspect
    import logging
    import math
    import os
    import sys
    import tempfile
    import threading
    import traceback
    import types
    import uuid
    import warnings
    import weakref
    from collections import defaultdict, deque
    from collections.abc import (
        Awaitable,
        Callable,
        Container,
        Coroutine,
        Generator,
        Hashable,
    )
    from enum import Enum
    from functools import wraps
    from typing import TYPE_CHECKING, Any, ClassVar, Literal, TypedDict, TypeVar, final

    import tblib
    from tlz import merge
    from tornado.ioloop import IOLoop

    import dask
    from dask.utils import parse_timedelta

    from distributed import profile, protocol
    from distributed._async_taskgroup import AsyncTaskGroup, AsyncTaskGroupClosedError
    from distributed.comm import (
        Comm,
        CommClosedError,
        connect,
        get_address_host_port,
        listen,
        normalize_address,
        unparse_host_port,
    )
    from distributed.comm.core import Listener
    from distributed.compatibility import PeriodicCallback
    from distributed.counter import Counter
    from distributed.diskutils import WorkDir, WorkSpace
    from distributed.metrics import context_meter, time
    from distributed.system_monitor import SystemMonitor
    from distributed.utils import (
        NoOpAwaitable,
        get_traceback,
        has_keyword,
        import_file,
        iscoroutinefunction,
        offload,
        recursive_to_dict,
        truncate_exception,
        wait_for,
        warn_on_duration,
    )

    if TYPE_CHECKING:
        from typing_extensions import ParamSpec, Self

        from distributed.counter import Digest

        P = ParamSpec("P")
        R = TypeVar("R")
        T = TypeVar("T")
        Coro = Coroutine[Any, Any, T]

    class Status(Enum):
        """
        This Enum contains the various states a cluster, worker, scheduler and nanny can be
        in. Some of the status can only be observed in one of cluster, nanny, scheduler or
        worker but we put them in the same Enum as they are compared with each
        other.
        """

        undefined = "undefined"
        created = "created"
        init = "init"
        starting = "starting"
        running = "running"
        paused = "paused"
        stopping = "stopping"
        stopped = "stopped"
        closing = "closing"
        closing_gracefully = "closing_gracefully"
        closed = "closed"
        failed = "failed"
        dont_reply = "dont_reply"

    Status.lookup = {s.name: s for s in Status}  # type: ignore

    class RPCClosed(IOError):
        pass

    logger = logging.getLogger(__name__)

    def raise_later(exc):
        def _raise(*args, **kwargs):
            raise exc

        return _raise

    tick_maximum_delay = parse_timedelta(
        dask.config.get("distributed.admin.tick.limit"), default="ms"
    )

    LOG_PDB = dask.config.get("distributed.admin.pdb-on-err")

    @functools.cache
    def _expects_comm(func: Callable) -> bool:
        sig = inspect.signature(func)
        params = list(sig.parameters)
        if params and params[0] == "comm":
            return True
        if params and params[0] == "stream":
            warnings.warn(
                "Calling the first argument of a RPC handler `stream` is "
                "deprecated. Defining this argument is optional. Either remove the "
                f"argument or rename it to `comm` in {func}.",
                FutureWarning,
            )
            return True
        return False

    class Server:
        """Dask Distributed Server

        Superclass for endpoints in a distributed cluster, such as Worker
        and Scheduler objects.

        **Handlers**

        Servers define operations with a ``handlers`` dict mapping operation names
        to functions.  The first argument of a handler function will be a ``Comm``
        for the communication established with the client.  Other arguments
        will receive inputs from the keys of the incoming message which will
        always be a dictionary.

        >>> def pingpong(comm):
        ...     return b'pong'

        >>> def add(comm, x, y):
        ...     return x + y

        >>> handlers = {'ping': pingpong, 'add': add}
        >>> server = Server(handlers)  # doctest: +SKIP
        >>> server.listen('tcp://0.0.0.0:8000')  # doctest: +SKIP

        **Message Format**

        The server expects messages to be dictionaries with a special key, `'op'`
        that corresponds to the name of the operation, and other key-value pairs as
        required by the function.

        So in the example above the following would be good messages.

        *  ``{'op': 'ping'}``
        *  ``{'op': 'add', 'x': 10, 'y': 20}``

        """

        _is_finalizing: staticmethod[[], bool] = staticmethod(sys.is_finalizing)

        default_ip: ClassVar[str] = ""
        default_port: ClassVar[int] = 0

        id: str
        blocked_handlers: list[str]
        handlers: dict[str, Callable]
        stream_handlers: dict[str, Callable]
        listeners: list[Listener]
        counters: defaultdict[str, Counter]
        deserialize: bool

        local_directory: str

        monitor: SystemMonitor
        io_loop: IOLoop
        thread_id: int

        periodic_callbacks: dict[str, PeriodicCallback]
        digests: defaultdict[Hashable, Digest] | None
        digests_total: defaultdict[Hashable, float]
        digests_total_since_heartbeat: defaultdict[Hashable, float]
        digests_max: defaultdict[Hashable, float]

        _last_tick: float
        _tick_counter: int
        _last_tick_counter: int
        _tick_interval: float
        _tick_interval_observed: float

        _status: Status

        _address: str | None
        _listen_address: str | None
        _host: str | None
        _port: int | None

        _comms: dict[Comm, str | None]

        _ongoing_background_tasks: AsyncTaskGroup
        _event_finished: asyncio.Event

        _original_local_dir: str
        _updated_sys_path: bool
        _workspace: WorkSpace
        _workdir: None | WorkDir

        _startup_lock: asyncio.Lock
        __startup_exc: Exception | None

        def __init__(
            self,
            handlers,
            blocked_handlers=None,
            stream_handlers=None,
            connection_limit=512,
            deserialize=True,
            serializers=None,
            deserializers=None,
            connection_args=None,
            timeout=None,
            io_loop=None,
            local_directory=None,
            needs_workdir=True,
        ):
            if local_directory is None:
                local_directory = (
                    dask.config.get("temporary-directory") or tempfile.gettempdir()
                )

            if "dask-scratch-space" not in str(local_directory):
                local_directory = os.path.join(local_directory, "dask-scratch-space")

            self._original_local_dir = local_directory

            with warn_on_duration(
                "1s",
                "Creating scratch directories is taking a surprisingly long time. ({duration:.2f}s) "
                "This is often due to running workers on a network file system. "
                "Consider specifying a local-directory to point workers to write "
                "scratch data to a local disk.",
            ):
                self._workspace = WorkSpace(local_directory)

                if not needs_workdir:  # eg. Nanny will not need a WorkDir
                    self._workdir = None
                    self.local_directory = self._workspace.base_dir
                else:
                    name = type(self).__name__.lower()
                    self._workdir = self._workspace.new_work_dir(prefix=f"{name}-")
                    self.local_directory = self._workdir.dir_path

            self._updated_sys_path = False
            if self.local_directory not in sys.path:
                sys.path.insert(0, self.local_directory)
                self._updated_sys_path = True

            if io_loop is not None:
                warnings.warn(
                    "The io_loop kwarg to Server is ignored and will be deprecated",
                    DeprecationWarning,
                    stacklevel=2,
                )

            self._status = Status.init
            self.handlers = {
                "identity": self.identity,
                "echo": self.echo,
                "connection_stream": self.handle_stream,
                "dump_state": self._to_dict,
            }
            self.handlers.update(handlers)
            if blocked_handlers is None:
                blocked_handlers = dask.config.get(
                    "distributed.%s.blocked-handlers" % type(self).__name__.lower(), []
                )
            self.blocked_handlers = blocked_handlers
            self.stream_handlers = {}
            self.stream_handlers.update(stream_handlers or {})

            self.id = type(self).__name__ + "-" + str(uuid.uuid4())
            self._address = None
            self._listen_address = None
            self._port = None
            self._host = None
            self._comms = {}
            self.deserialize = deserialize
            self.monitor = SystemMonitor()
            self._ongoing_background_tasks = AsyncTaskGroup()
            self._event_finished = asyncio.Event()

            self.listeners = []
            self.io_loop = self.loop = IOLoop.current()

            if not hasattr(self.io_loop, "profile"):
                if (
                    dask.config.get("distributed.worker.profile.enabled")
                    and sys.version_info.minor != 11
                ):
                    ref = weakref.ref(self.io_loop)

                    def stop() -> bool:
                        loop = ref()
                        return loop is None or loop.asyncio_loop.is_closed()

                    self.io_loop.profile = profile.watch(
                        omit=("profile.py", "selectors.py"),
                        interval=dask.config.get("distributed.worker.profile.interval"),
                        cycle=dask.config.get("distributed.worker.profile.cycle"),
                        stop=stop,
                    )
                else:
                    self.io_loop.profile = deque()

            self.periodic_callbacks = {}

            # Statistics counters for various events
            try:
                from distributed.counter import Digest

                self.digests = defaultdict(Digest)
            except ImportError:
                self.digests = None

            # Also log cumulative totals (reset at server restart)
            # and local maximums (reset by prometheus poll)
            # Don't cast int metrics to float
            self.digests_total = defaultdict(int)
            self.digests_total_since_heartbeat = defaultdict(int)
            self.digests_max = defaultdict(int)

            self.counters = defaultdict(Counter)
            pc = PeriodicCallback(self._shift_counters, 5000)
            self.periodic_callbacks["shift_counters"] = pc

            pc = PeriodicCallback(
                self.monitor.update,
                parse_timedelta(
                    dask.config.get("distributed.admin.system-monitor.interval")
                )
                * 1000,
            )
            self.periodic_callbacks["monitor"] = pc

            self._last_tick = time()
            self._tick_counter = 0
            self._last_tick_counter = 0
            self._last_tick_cycle = time()
            self._tick_interval = parse_timedelta(
                dask.config.get("distributed.admin.tick.interval"), default="ms"
            )
            self._tick_interval_observed = self._tick_interval
            self.periodic_callbacks["tick"] = PeriodicCallback(
                self._measure_tick, self._tick_interval * 1000
            )
            self.periodic_callbacks["ticks"] = PeriodicCallback(
                self._cycle_ticks,
                parse_timedelta(dask.config.get("distributed.admin.tick.cycle")) * 1000,
            )

            self.thread_id = 0

            def set_thread_ident():
                self.thread_id = threading.get_ident()

            self.io_loop.add_callback(set_thread_ident)
            self._startup_lock = asyncio.Lock()
            self.__startup_exc = None

            self.rpc = ConnectionPool(
                limit=connection_limit,
                deserialize=deserialize,
                serializers=serializers,
                deserializers=deserializers,
                connection_args=connection_args,
                timeout=timeout,
                server=self,
            )

            self.__stopped = False

        async def upload_file(
            self, filename: str, data: str | bytes, load: bool = True
        ) -> dict[str, Any]:
            out_filename = os.path.join(self.local_directory, filename)

            def func(data):
                if isinstance(data, str):
                    data = data.encode()
                with open(out_filename, "wb") as f:
                    f.write(data)
                    f.flush()
                    os.fsync(f.fileno())
                return data

            if len(data) < 10000:
                data = func(data)
            else:
                data = await offload(func, data)

            if load:
                try:
                    import_file(out_filename)
                except Exception as e:
                    logger.exception(e)
                    raise e

            return {"status": "OK", "nbytes": len(data)}

        def _shift_counters(self):
            # Copy counters before iterating to avoid concurrent modification
            for counter in list(self.counters.values()):
                counter.shift()
            if self.digests is not None:
                # Copy digests before iterating to avoid concurrent modification
                for digest in list(self.digests.values()):
                    digest.shift()

        @property
        def status(self) -> Status:
            try:
                return self._status
            except AttributeError:
                return Status.undefined

        @status.setter
        def status(self, value: Status) -> None:
            if not isinstance(value, Status):
                raise TypeError(f"Expected Status; got {value!r}")
            self._status = value

        @property
        def incoming_comms_open(self) -> int:
            """The number of total incoming connections listening to remote RPCs"""
            return len(self._comms)

        @property
        def incoming_comms_active(self) -> int:
            """The number of connections currently handling a remote RPC"""
            return len([c for c, op in self._comms.items() if op is not None])

        @property
        def outgoing_comms_open(self) -> int:
            """The number of connections currently open and waiting for a remote RPC"""
            return self.rpc.open

        @property
        def outgoing_comms_active(self) -> int:
            """The number of outgoing connections that are currently used to
            execute a RPC"""
            return self.rpc.active

        def get_connection_counters(self) -> dict[str, int]:
            """A dict with various connection counters

            See also
            --------
            Server.incoming_comms_open
            Server.incoming_comms_active
            Server.outgoing_comms_open
            Server.outgoing_comms_active
            """
            return {
                attr: getattr(self, attr)
                for attr in [
                    "incoming_comms_open",
                    "incoming_comms_active",
                    "outgoing_comms_open",
                    "outgoing_comms_active",
                ]
            }

        async def finished(self):
            """Wait until the server has finished"""
            await self._event_finished.wait()

        def __await__(self):
            return self.start().__await__()

        async def start_unsafe(self):
            """Attempt to start the server. This is not idempotent and not protected against concurrent startup attempts.

            This is intended to be overwritten or called by subclasses. For a safe
            startup, please use ``Server.start`` instead.

            If ``death_timeout`` is configured, we will require this coroutine to
            finish before this timeout is reached. If the timeout is reached we will
            close the instance and raise an ``asyncio.TimeoutError``
            """
            await self.rpc.start()
            return self

        @final
        async def start(self):
            async with self._startup_lock:
                if self.status == Status.failed:
                    assert self.__startup_exc is not None
                    raise self.__startup_exc
                elif self.status != Status.init:
                    return self
                timeout = getattr(self, "death_timeout", None)

                async def _close_on_failure(exc: Exception) -> None:
                    await self.close(reason=f"failure-to-start-{str(type(exc))}")
                    self.status = Status.failed
                    self.__startup_exc = exc

                try:
                    await wait_for(self.start_unsafe(), timeout=timeout)
                except asyncio.TimeoutError as exc:
                    await _close_on_failure(exc)
                    raise asyncio.TimeoutError(
                        f"{type(self).__name__} start timed out after {timeout}s."
                    ) from exc
                except Exception as exc:
                    await _close_on_failure(exc)
                    raise RuntimeError(f"{type(self).__name__} failed to start.") from exc
                if self.status == Status.init:
                    self.status = Status.running
            return self

        async def __aenter__(self):
            await self
            return self

        async def __aexit__(self, exc_type, exc_value, traceback):
            await self.close()

        def start_periodic_callbacks(self):
            """Start Periodic Callbacks consistently

            This starts all PeriodicCallbacks stored in self.periodic_callbacks if
            they are not yet running. It does this safely by checking that it is using the
            correct event loop.
            """
            if self.io_loop.asyncio_loop is not asyncio.get_running_loop():
                raise RuntimeError(f"{self!r} is bound to a different event loop")

            self._last_tick = time()
            for pc in self.periodic_callbacks.values():
                if not pc.is_running():
                    pc.start()

        def _stop_listeners(self) -> asyncio.Future:
            listeners_to_stop: set[Awaitable] = set()

            for listener in self.listeners:
                future = listener.stop()
                if inspect.isawaitable(future):
                    warnings.warn(
                        f"{type(listener)} is using an asynchronous `stop` method. "
                        "Support for asynchronous `Listener.stop` has been deprecated and "
                        "will be removed in a future version",
                        DeprecationWarning,
                    )
                    listeners_to_stop.add(future)
                elif hasattr(listener, "abort_handshaking_comms"):
                    listener.abort_handshaking_comms()

            return asyncio.gather(*listeners_to_stop)

        def stop(self) -> None:
            if self.__stopped:
                return
            self.__stopped = True
            self.monitor.close()
            if not (stop_listeners := self._stop_listeners()).done():
                self._ongoing_background_tasks.call_soon(
                    asyncio.wait_for(stop_listeners, timeout=None)  # type: ignore[arg-type]
                )
            if self._workdir is not None:
                self._workdir.release()

        @property
        def listener(self) -> Listener | None:
            if self.listeners:
                return self.listeners[0]
            else:
                return None

        def _measure_tick(self):
            now = time()
            tick_duration = now - self._last_tick
            self._last_tick = now
            self._tick_counter += 1
            # This metric is exposed in Prometheus and is reset there during
            # collection
            if tick_duration > tick_maximum_delay:
                logger.info(
                    "Event loop was unresponsive in %s for %.2fs.  "
                    "This is often caused by long-running GIL-holding "
                    "functions or moving large chunks of data. "
                    "This can cause timeouts and instability.",
                    type(self).__name__,
                    tick_duration,
                )
            self.digest_metric("tick-duration", tick_duration)

        def _cycle_ticks(self):
            if not self._tick_counter:
                return
            now = time()
            last_tick_cycle, self._last_tick_cycle = self._last_tick_cycle, now
            count = self._tick_counter - self._last_tick_counter
            self._last_tick_counter = self._tick_counter
            self._tick_interval_observed = (now - last_tick_cycle) / (count or 1)

        @property
        def address(self) -> str:
            """
            The address this Server can be contacted on.
            If the server is not up, yet, this raises a ValueError.
            """
            if not self._address:
                if self.listener is None:
                    raise ValueError("cannot get address of non-running Server")
                self._address = self.listener.contact_address
                assert self._address
            return self._address

        @property
        def address_safe(self) -> str:
            """
            The address this Server can be contacted on.
            If the server is not up, yet, this returns a ``"not-running"``.
            """
            try:
                return self.address
            except ValueError:
                return "not-running"

        @property
        def listen_address(self):
            """
            The address this Server is listening on.  This may be a wildcard
            address such as `tcp://0.0.0.0:1234`.
            """
            if not self._listen_address:
                if self.listener is None:
                    raise ValueError("cannot get listen address of non-running Server")
                self._listen_address = self.listener.listen_address
            return self._listen_address

        @property
        def host(self):
            """
            The host this Server is running on.

            This will raise ValueError if the Server is listening on a
            non-IP based protocol.
            """
            if not self._host:
                self._host, self._port = get_address_host_port(self.address)
            return self._host

        @property
        def port(self):
            """
            The port number this Server is listening on.

            This will raise ValueError if the Server is listening on a
            non-IP based protocol.
            """
            if not self._port:
                self._host, self._port = get_address_host_port(self.address)
            return self._port

        def identity(self) -> dict[str, str]:
            return {"type": type(self).__name__, "id": self.id}

        def _to_dict(self, *, exclude: Container[str] = ()) -> dict[str, Any]:
            """Dictionary representation for debugging purposes.
            Not type stable and not intended for roundtrips.

            See also
            --------
            Server.identity
            Client.dump_cluster_state
            distributed.utils.recursive_to_dict
            """
            info: dict[str, Any] = self.identity()
            extra = {
                "address": self.address,
                "status": self.status.name,
                "thread_id": self.thread_id,
            }
            info.update(extra)
            info = {k: v for k, v in info.items() if k not in exclude}
            return recursive_to_dict(info, exclude=exclude)

        def echo(self, data=None):
            return data

        async def listen(self, port_or_addr=None, allow_offload=True, **kwargs):
            if port_or_addr is None:
                port_or_addr = self.default_port
            if isinstance(port_or_addr, int):
                addr = unparse_host_port(self.default_ip, port_or_addr)
            elif isinstance(port_or_addr, tuple):
                addr = unparse_host_port(*port_or_addr)
            else:
                addr = port_or_addr
                assert isinstance(addr, str)
            listener = await listen(
                addr,
                self.handle_comm,
                deserialize=self.deserialize,
                allow_offload=allow_offload,
                **kwargs,
            )
            self.listeners.append(listener)

        def handle_comm(self, comm: Comm) -> NoOpAwaitable:
            """Start a background task that dispatches new communications to coroutine-handlers"""
            try:
                self._ongoing_background_tasks.call_soon(self._handle_comm, comm)
            except AsyncTaskGroupClosedError:
                comm.abort()
            return NoOpAwaitable()

        async def _handle_comm(self, comm: Comm) -> None:
            """Dispatch new communications to coroutine-handlers

            Handlers is a dictionary mapping operation names to functions or
            coroutines.

                {'get_data': get_data,
                 'ping': pingpong}

            Coroutines should expect a single Comm object.
            """
            if self.__stopped:
                comm.abort()
                return
            address = comm.peer_address
            op = None

            logger.debug("Connection from %r to %s", address, type(self).__name__)
            self._comms[comm] = op

            await self
            try:
                while not self.__stopped:
                    try:
                        msg = await comm.read()
                        logger.debug("Message from %r: %s", address, msg)
                    except OSError as e:
                        if not self._is_finalizing():
                            logger.debug(
                                "Lost connection to %r while reading message: %s."
                                " Last operation: %s",
                                address,
                                e,
                                op,
                            )
                        break
                    except Exception as e:
                        logger.exception("Exception while reading from %s", address)
                        if comm.closed():
                            raise
                        else:
                            await comm.write(error_message(e, status="uncaught-error"))
                            continue
                    if not isinstance(msg, dict):
                        raise TypeError(
                            "Bad message type.  Expected dict, got\n  " + str(msg)
                        )

                    try:
                        op = msg.pop("op")
                    except KeyError as e:
                        raise ValueError(
                            "Received unexpected message without 'op' key: " + str(msg)
                        ) from e
                    if self.counters is not None:
                        self.counters["op"].add(op)
                    self._comms[comm] = op
                    serializers = msg.pop("serializers", None)
                    close_desired = msg.pop("close", False)
                    reply = msg.pop("reply", True)
                    if op == "close":
                        if reply:
                            await comm.write("OK")
                        break

                    result = None
                    try:
                        if op in self.blocked_handlers:
                            _msg = (
                                "The '{op}' handler has been explicitly disallowed "
                                "in {obj}, possibly due to security concerns."
                            )
                            exc = ValueError(_msg.format(op=op, obj=type(self).__name__))
                            handler = raise_later(exc)
                        else:
                            handler = self.handlers[op]
                    except KeyError:
                        logger.warning(
                            "No handler %s found in %s",
                            op,
                            type(self).__name__,
                            exc_info=True,
                        )
                    else:
                        if serializers is not None and has_keyword(handler, "serializers"):
                            msg["serializers"] = serializers  # add back in

                        logger.debug("Calling into handler %s", handler.__name__)
                        try:
                            if _expects_comm(handler):
                                result = handler(comm, **msg)
                            else:
                                result = handler(**msg)
                            if inspect.iscoroutine(result):
                                result = await result
                            elif inspect.isawaitable(result):
                                raise RuntimeError(
                                    f"Comm handler returned unknown awaitable. Expected coroutine, instead got {type(result)}"
                                )
                        except CommClosedError:
                            if self.status == Status.running:
                                logger.info("Lost connection to %r", address, exc_info=True)
                            break
                        except Exception as e:
                            logger.exception("Exception while handling op %s", op)
                            if comm.closed():
                                raise
                            else:
                                result = error_message(e, status="uncaught-error")

                    if reply and result != Status.dont_reply:
                        try:
                            await comm.write(result, serializers=serializers)
                        except (OSError, TypeError) as e:
                            logger.debug(
                                "Lost connection to %r while sending result for op %r: %s",
                                address,
                                op,
                                e,
                            )
                            break

                    self._comms[comm] = None
                    msg = result = None
                    if close_desired:
                        await comm.close()
                    if comm.closed():
                        break

            finally:
                del self._comms[comm]
                if not self._is_finalizing() and not comm.closed():
                    try:
                        comm.abort()
                    except Exception as e:
                        logger.error(
                            "Failed while closing connection to %r: %s", address, e
                        )

        async def handle_stream(
            self, comm: Comm, extra: dict[str, Any] | None = None
        ) -> None:
            extra = extra or {}
            logger.info("Starting established connection to %s", comm.peer_address)

            closed = False
            try:
                while not closed:
                    try:
                        msgs = await comm.read()
                    # If another coroutine has closed the comm, stop handling the stream.
                    except CommClosedError:
                        closed = True
                        logger.info(
                            "Connection to %s has been closed.",
                            comm.peer_address,
                        )
                        break
                    if not isinstance(msgs, (tuple, list)):
                        msgs = (msgs,)

                    for msg in msgs:
                        if msg == "OK":
                            break
                        op = msg.pop("op")
                        if op:
                            if op == "close-stream":
                                closed = True
                                logger.info(
                                    "Received 'close-stream' from %s; closing.",
                                    comm.peer_address,
                                )
                                break
                            handler = self.stream_handlers[op]
                            if iscoroutinefunction(handler):
                                await handler(**merge(extra, msg))
                            else:
                                handler(**merge(extra, msg))
                        else:
                            logger.error("odd message %s", msg)
                    await asyncio.sleep(0)
            except Exception:
                if LOG_PDB:
                    import pdb

                    pdb.set_trace()
                raise
            finally:
                await comm.close()
                assert comm.closed()

        async def close(self, timeout: float | None = None, reason: str = "") -> None:
            try:
                for pc in self.periodic_callbacks.values():
                    pc.stop()

                self.__stopped = True
                self.monitor.close()
                await self._stop_listeners()

                # TODO: Deal with exceptions
                await self._ongoing_background_tasks.stop()

                await self.rpc.close()
                await asyncio.gather(*[comm.close() for comm in list(self._comms)])

                # Remove scratch directory from global sys.path
                if self._updated_sys_path and sys.path[0] == self.local_directory:
                    sys.path.remove(self.local_directory)
            finally:
                self._event_finished.set()

        def digest_metric(self, name: Hashable, value: float) -> None:
            # Granular data (requires crick)
            if self.digests is not None:
                self.digests[name].add(value)
            # Cumulative data (reset by server restart)
            self.digests_total[name] += value
            # Cumulative data sent to scheduler and reset on heartbeat
            self.digests_total_since_heartbeat[name] += value
            # Local maximums (reset by Prometheus poll)
            self.digests_max[name] = max(self.digests_max[name], value)

    def context_meter_to_server_digest(digest_tag: str) -> Callable:
        """Decorator for an async method of a Server subclass that calls
        ``distributed.metrics.context_meter.meter`` and/or ``digest_metric``.
        It routes the calls from ``context_meter.digest_metric(label, value, unit)`` to
        ``Server.digest_metric((digest_tag, label, unit), value)``.
        """

        def decorator(func: Callable) -> Callable:
            @wraps(func)
            async def wrapper(self: Server, *args: Any, **kwargs: Any) -> Any:
                def metrics_callback(label: Hashable, value: float, unit: str) -> None:
                    if not isinstance(label, tuple):
                        label = (label,)
                    name = (digest_tag, *label, unit)
                    self.digest_metric(name, value)

                with context_meter.add_callback(metrics_callback, allow_offload=True):
                    return await func(self, *args, **kwargs)

            return wrapper

        return decorator

    def pingpong(comm):
        return b"pong"

    async def send_recv(  # type: ignore[no-untyped-def]
        comm: Comm,
        *,
        reply: bool = True,
        serializers=None,
        deserializers=None,
        **kwargs,
    ):
        """Send and recv with a Comm.

        Keyword arguments turn into the message

        response = await send_recv(comm, op='ping', reply=True)
        """
        msg = kwargs
        msg["reply"] = reply
        please_close = kwargs.get("close", False)
        force_close = False
        if deserializers is None:
            deserializers = serializers
        if deserializers is not None:
            msg["serializers"] = deserializers

        try:
            await comm.write(msg, serializers=serializers, on_error="raise")
            if reply:
                response = await comm.read(deserializers=deserializers)
            else:
                response = None
        except (asyncio.TimeoutError, OSError):
            # On communication errors, we should simply close the communication
            # Note that OSError includes CommClosedError and socket timeouts
            force_close = True
            raise
        except asyncio.CancelledError:
            # Do not reuse the comm to prevent the next call of send_recv from receiving
            # data from this call and/or accidentally putting multiple waiters on read().
            # Note that this relies on all Comm implementations to allow a write() in the
            # middle of a read().
            please_close = True
            raise
        finally:
            if force_close:
                comm.abort()
            elif please_close:
                await comm.close()

        if isinstance(response, dict) and response.get("status") == "uncaught-error":
            if comm.deserialize:
                _, exc, tb = clean_exception(**response)
                assert exc
                raise exc.with_traceback(tb)
            else:
                raise Exception(response["exception_text"])
        return response

    def addr_from_args(
        addr: str | tuple[str, int | None] | None = None,
        ip: str | None = None,
        port: int | None = None,
    ) -> str:
        if addr is None:
            assert ip is not None
            return normalize_address(unparse_host_port(ip, port))

        assert ip is None and port is None
        if isinstance(addr, tuple):
            return normalize_address(unparse_host_port(*addr))

        return normalize_address(addr)

    class rpc:
        """Conveniently interact with a remote server

        >>> remote = rpc(address)  # doctest: +SKIP
        >>> response = await remote.add(x=10, y=20)  # doctest: +SKIP

        One rpc object can be reused for several interactions.
        Additionally, this object creates and destroys many comms as necessary
        and so is safe to use in multiple overlapping communications.

        When done, close comms explicitly.

        >>> remote.close_comms()  # doctest: +SKIP
        """

        active: ClassVar[weakref.WeakSet[rpc]] = weakref.WeakSet()
        comms = ()
        address = None

        def __init__(
            self,
            arg=None,
            comm=None,
            deserialize=True,
            timeout=None,
            connection_args=None,
            serializers=None,
            deserializers=None,
        ):
            self.comms = {}
            self.address = coerce_to_address(arg)
            self.timeout = timeout
            self.status = Status.running
            self.deserialize = deserialize
            self.serializers = serializers
            self.deserializers = deserializers if deserializers is not None else serializers
            self.connection_args = connection_args or {}
            self._created = weakref.WeakSet()
            rpc.active.add(self)

        async def live_comm(self):
            """Get an open communication

            Some comms to the ip/port target may be in current use by other
            coroutines.  We track this with the `comms` dict

                :: {comm: True/False if open and ready for use}

            This function produces an open communication, either by taking one
            that we've already made or making a new one if they are all taken.
            This also removes comms that have been closed.

            When the caller is done with the stream they should set

                self.comms[comm] = True

            As is done in __getattr__ below.
            """
            if self.status == Status.closed:
                raise RPCClosed("RPC Closed")
            to_clear = set()
            open = False
            for comm, open in self.comms.items():
                if comm.closed():
                    to_clear.add(comm)
                if open:
                    break
            for s in to_clear:
                del self.comms[s]
            if not open or comm.closed():
                comm = await connect(
                    self.address,
                    self.timeout,
                    deserialize=self.deserialize,
                    **self.connection_args,
                )
                comm.name = "rpc"
            self.comms[comm] = False  # mark as taken
            return comm

        def close_comms(self):
            async def _close_comm(comm):
                # Make sure we tell the peer to close
                try:
                    if not comm.closed():
                        await comm.write({"op": "close", "reply": False})
                        await comm.close()
                except OSError:
                    comm.abort()

            tasks = []
            for comm in list(self.comms):
                if comm and not comm.closed():
                    task = asyncio.ensure_future(_close_comm(comm))
                    tasks.append(task)
            for comm in list(self._created):
                if comm and not comm.closed():
                    task = asyncio.ensure_future(_close_comm(comm))
                    tasks.append(task)

            self.comms.clear()
            return tasks

        def __getattr__(self, key):
            async def send_recv_from_rpc(**kwargs):
                if self.serializers is not None and kwargs.get("serializers") is None:
                    kwargs["serializers"] = self.serializers
                if self.deserializers is not None and kwargs.get("deserializers") is None:
                    kwargs["deserializers"] = self.deserializers
                comm = None
                try:
                    comm = await self.live_comm()
                    comm.name = "rpc." + key
                    result = await send_recv(comm=comm, op=key, **kwargs)
                except (RPCClosed, CommClosedError) as e:
                    if comm:
                        raise type(e)(
                            f"Exception while trying to call remote method {key!r} using comm {comm!r}."
                        ) from e
                    else:
                        raise type(e)(
                            f"Exception while trying to call remote method {key!r} before comm was established."
                        ) from e

                self.comms[comm] = True  # mark as open
                return result

            return send_recv_from_rpc

        async def close_rpc(self):
            if self.status != Status.closed:
                rpc.active.discard(self)
            self.status = Status.closed
            return await asyncio.gather(*self.close_comms())

        def __enter__(self):
            warnings.warn(
                "the rpc synchronous context manager is deprecated",
                DeprecationWarning,
                stacklevel=2,
            )
            return self

        def __exit__(self, exc_type, exc_value, traceback):
            asyncio.ensure_future(self.close_rpc())

        async def __aenter__(self):
            return self

        async def __aexit__(self, exc_type, exc_value, traceback):
            await self.close_rpc()

        def __del__(self):
            if self.status != Status.closed:
                rpc.active.discard(self)
                self.status = Status.closed
                still_open = [comm for comm in self.comms if not comm.closed()]
                if still_open:
                    logger.warning(
                        "rpc object %s deleted with %d open comms", self, len(still_open)
                    )
                    for comm in still_open:
                        comm.abort()

        def __repr__(self):
            return "<rpc to %r, %d comms>" % (self.address, len(self.comms))

    class PooledRPCCall:
        """The result of ConnectionPool()('host:port')

        See Also:
            ConnectionPool
        """

        def __init__(self, addr, pool, serializers=None, deserializers=None):
            self.addr = addr
            self.pool = pool
            self.serializers = serializers
            self.deserializers = deserializers if deserializers is not None else serializers

        @property
        def address(self):
            return self.addr

        def __getattr__(self, key):
            async def send_recv_from_rpc(**kwargs):
                if self.serializers is not None and kwargs.get("serializers") is None:
                    kwargs["serializers"] = self.serializers
                if self.deserializers is not None and kwargs.get("deserializers") is None:
                    kwargs["deserializers"] = self.deserializers
                comm = await self.pool.connect(self.addr)
                prev_name, comm.name = comm.name, "ConnectionPool." + key
                try:
                    return await send_recv(comm=comm, op=key, **kwargs)
                finally:
                    self.pool.reuse(self.addr, comm)
                    comm.name = prev_name

            return send_recv_from_rpc

        async def close_rpc(self):
            pass

        # For compatibility with rpc()
        def __enter__(self):
            warnings.warn(
                "the rpc synchronous context manager is deprecated",
                DeprecationWarning,
                stacklevel=2,
            )
            return self

        def __exit__(self, exc_type, exc_value, traceback):
            pass

        async def __aenter__(self):
            return self

        async def __aexit__(self, *args):
            pass

        def __repr__(self):
            return f"<pooled rpc to {self.addr!r}>"

    class ConnectionPool:
        """A maximum sized pool of Comm objects.

        This provides a connect method that mirrors the normal distributed.connect
        method, but provides connection sharing and tracks connection limits.

        This object provides an ``rpc`` like interface::

            >>> rpc = ConnectionPool(limit=512)
            >>> scheduler = rpc('127.0.0.1:8786')
            >>> workers = [rpc(address) for address in ...]

            >>> info = await scheduler.identity()

        It creates enough comms to satisfy concurrent connections to any
        particular address::

            >>> a, b = await asyncio.gather(scheduler.who_has(), scheduler.has_what())

        It reuses existing comms so that we don't have to continuously reconnect.

        It also maintains a comm limit to avoid "too many open file handle"
        issues.  Whenever this maximum is reached we clear out all idling comms.
        If that doesn't do the trick then we wait until one of the occupied comms
        closes.

        Parameters
        ----------
        limit: int
            The number of open comms to maintain at once
        deserialize: bool
            Whether or not to deserialize data by default or pass it through
        """

        _instances: ClassVar[weakref.WeakSet[ConnectionPool]] = weakref.WeakSet()

        def __init__(
            self,
            limit: int = 512,
            deserialize: bool = True,
            serializers: list[str] | None = None,
            allow_offload: bool = True,
            deserializers: list[str] | None = None,
            connection_args: dict[str, object] | None = None,
            timeout: float | None = None,
            server: object = None,
        ) -> None:
            self.limit = limit  # Max number of open comms
            # Invariant: len(available) == open - active
            self.available: defaultdict[str, set[Comm]] = defaultdict(set)
            # Invariant: len(occupied) == active
            self.occupied: defaultdict[str, set[Comm]] = defaultdict(set)
            self.allow_offload = allow_offload
            self.deserialize = deserialize
            self.serializers = serializers
            self.deserializers = deserializers if deserializers is not None else serializers
            self.connection_args = connection_args or {}
            self.timeout = timeout
            self.server = weakref.ref(server) if server else None
            self._created: weakref.WeakSet[Comm] = weakref.WeakSet()
            self._instances.add(self)
            # _n_connecting and _connecting have subtle different semantics. The set
            # _connecting contains futures actively trying to establish a connection
            # while the _n_connecting also accounts for connection attempts which
            # are waiting due to the connection limit
            self._connecting: defaultdict[str, set[Callable[[str], None]]] = defaultdict(
                set
            )
            self._pending_count = 0
            self._connecting_count = 0
            self._connecting_close_timeout = 5
            self.status = Status.init

        def _validate(self) -> None:
            """
            Validate important invariants of this class

            Used only for testing / debugging
            """
            assert self.semaphore._value == self.limit - self.open - self._n_connecting

        @property
        def active(self) -> int:
            return sum(map(len, self.occupied.values()))

        @property
        def open(self) -> int:
            return self.active + sum(map(len, self.available.values()))

        def __repr__(self) -> str:
            return "<ConnectionPool: open=%d, active=%d, connecting=%d>" % (
                self.open,
                self.active,
                len(self._connecting),
            )

        def __call__(
            self,
            addr: str | tuple[str, int | None] | None = None,
            ip: str | None = None,
            port: int | None = None,
        ) -> PooledRPCCall:
            """Cached rpc objects"""
            addr = addr_from_args(addr=addr, ip=ip, port=port)
            return PooledRPCCall(
                addr, self, serializers=self.serializers, deserializers=self.deserializers
            )

        def __await__(self) -> Generator[Any, Any, Self]:
            async def _() -> Self:
                await self.start()
                return self

            return _().__await__()

        async def __aenter__(self):
            await self
            return self

        async def __aexit__(self, *args):
            await self.close()
            return

        async def start(self) -> None:
            # Invariant: semaphore._value == limit - open - _n_connecting
            self.semaphore = asyncio.Semaphore(self.limit)
            self.status = Status.running

        @property
        def _n_connecting(self) -> int:
            return self._connecting_count

        async def _connect(self, addr: str, timeout: float | None = None) -> Comm:
            self._pending_count += 1
            try:
                await self.semaphore.acquire()
                try:
                    self._connecting_count += 1
                    comm = await connect(
                        addr,
                        timeout=timeout or self.timeout,
                        deserialize=self.deserialize,
                        **self.connection_args,
                    )
                    comm.name = "ConnectionPool"
                    comm._pool = weakref.ref(self)
                    comm.allow_offload = self.allow_offload
                    self._created.add(comm)

                    self.occupied[addr].add(comm)

                    return comm
                except BaseException:
                    self.semaphore.release()
                    raise
                finally:
                    self._connecting_count -= 1
            finally:
                self._pending_count -= 1

        async def connect(self, addr: str, timeout: float | None = None) -> Comm:
            """
            Get a Comm to the given address.  For internal use.
            """
            if self.status != Status.running:
                raise RuntimeError("ConnectionPool is closed")
            available = self.available[addr]
            occupied = self.occupied[addr]
            while available:
                comm = available.pop()
                if comm.closed():
                    self.semaphore.release()
                else:
                    occupied.add(comm)
                    return comm

            if self.semaphore.locked():
                self.collect()

            # on 3.11 this uses asyncio.timeout as a cancel scope to avoid having
            # to track inner and outer CancelledError exceptions and correctly
            # call .uncancel() when a CancelledError is caught.
            if sys.version_info >= (3, 11):
                reason: str | None = None
                try:
                    async with asyncio.timeout(math.inf) as scope:

                        def cancel_timeout_cb(reason_: str) -> None:
                            nonlocal reason
                            reason = reason_
                            scope.reschedule(-1)

                        self._connecting[addr].add(cancel_timeout_cb)
                        try:
                            return await self._connect(addr=addr, timeout=timeout)
                        finally:
                            connecting = self._connecting[addr]
                            connecting.discard(cancel_timeout_cb)
                            if not connecting:
                                try:
                                    del self._connecting[addr]
                                except KeyError:
                                    pass
                except TimeoutError:
                    if reason is None:
                        raise
                    raise CommClosedError(reason)
            else:
                # This construction is there to ensure that cancellation requests from
                # the outside can be distinguished from cancellations of our own.
                # Once the CommPool closes, we'll cancel the connect_attempt which will
                # raise an OSError
                # If the ``connect`` is cancelled from the outside, the Event.wait will
                # be cancelled instead which we'll reraise as a CancelledError and allow
                # it to propagate
                connect_attempt = asyncio.create_task(self._connect(addr, timeout))
                done = asyncio.Event()
                reason = "ConnectionPool closing."

                def cancel_task_cb(reason_: str) -> None:
                    nonlocal reason
                    reason = reason_
                    connect_attempt.cancel()

                connecting = self._connecting[addr]
                connecting.add(cancel_task_cb)

                def callback(task: asyncio.Task[Comm]) -> None:
                    done.set()
                    connecting = self._connecting[addr]
                    connecting.discard(cancel_task_cb)

                    if not connecting:
                        try:
                            del self._connecting[addr]
                        except KeyError:  # pragma: no cover
                            pass

                connect_attempt.add_done_callback(callback)

                try:
                    await done.wait()
                except asyncio.CancelledError:
                    # This is an outside cancel attempt
                    connect_attempt.cancel()
                    await connect_attempt
                    raise
                try:
                    return connect_attempt.result()
                except asyncio.CancelledError:
                    if reason:
                        raise CommClosedError(reason)
                    raise

        def reuse(self, addr: str, comm: Comm) -> None:
            """
            Reuse an open communication to the given address.  For internal use.
            """
            # if the pool is asked to re-use a comm it does not know about, ignore
            # this comm: just close it.
            if comm not in self.occupied[addr]:
                IOLoop.current().add_callback(comm.close)
            else:
                self.occupied[addr].remove(comm)
                if comm.closed():
                    # Either the user passed the close=True parameter to send_recv, or
                    # the RPC call raised OSError or CancelledError
                    self.semaphore.release()
                else:
                    self.available[addr].add(comm)
                    if self.semaphore.locked() and self._pending_count:
                        self.collect()

        def collect(self) -> None:
            """
            Collect open but unused communications, to allow opening other ones.
            """
            logger.info(
                "Collecting unused comms.  open: %d, active: %d, connecting: %d",
                self.open,
                self.active,
                len(self._connecting),
            )
            for comms in self.available.values():
                for comm in comms:
                    IOLoop.current().add_callback(comm.close)
                    self.semaphore.release()
                comms.clear()

        def remove(self, addr: str, *, reason: str = "Address removed.") -> None:
            """
            Remove all Comms to a given address.
            """
            logger.debug("Removing comms to %s", addr)
            if addr in self.available:
                comms = self.available.pop(addr)
                for comm in comms:
                    IOLoop.current().add_callback(comm.close)
                    self.semaphore.release()
            if addr in self.occupied:
                comms = self.occupied.pop(addr)
                for comm in comms:
                    IOLoop.current().add_callback(comm.close)
                    self.semaphore.release()

            if addr in self._connecting:
                cbs = self._connecting[addr]
                for cb in cbs:
                    cb(reason)

        async def close(self) -> None:
            """
            Close all communications
            """
            self.status = Status.closed
            for cbs in self._connecting.values():
                for cb in cbs:
                    cb("ConnectionPool closing.")
            for d in [self.available, self.occupied]:
                comms = set()
                while d:
                    comms.update(d.popitem()[1])

                await asyncio.gather(
                    *(comm.close() for comm in comms), return_exceptions=True
                )

                for _ in comms:
                    self.semaphore.release()

            start = time()
            while self._connecting:
                if time() - start > self._connecting_close_timeout:
                    logger.warning(
                        "Pending connections refuse to cancel. %d connections pending. Closing anyway.",
                        len(self._connecting),
                    )
                    break
                await asyncio.sleep(0.01)

    def coerce_to_address(o):
        if isinstance(o, (list, tuple)):
            o = unparse_host_port(*o)

        return normalize_address(o)

    def collect_causes(e: BaseException) -> list[BaseException]:
        causes = []
        while e.__cause__ is not None:
            causes.append(e.__cause__)
            e = e.__cause__
        return causes

    class ErrorMessage(TypedDict):
        status: str
        exception: protocol.Serialize
        traceback: protocol.Serialize | None
        exception_text: str
        traceback_text: str

    class OKMessage(TypedDict):
        status: Literal["OK"]

    def error_message(e: BaseException, status: str = "error") -> ErrorMessage:
        """Produce message to send back given an exception has occurred

        This does the following:

        1.  Gets the traceback
        2.  Truncates the exception and the traceback
        3.  Serializes the exception and traceback or
        4.  If they can't be serialized send string versions
        5.  Format a message and return

        See Also
        --------
        clean_exception : deserialize and unpack message into exception/traceback
        """
        MAX_ERROR_LEN = dask.config.get("distributed.admin.max-error-length")
        tblib.pickling_support.install(e, *collect_causes(e))
        tb = get_traceback()
        tb_text = "".join(traceback.format_tb(tb))
        e = truncate_exception(e, MAX_ERROR_LEN)
        try:
            e_bytes = protocol.pickle.dumps(e)
            protocol.pickle.loads(e_bytes)
        except Exception:
            e_bytes = protocol.pickle.dumps(Exception(repr(e)))
        e_serialized = protocol.to_serialize(e_bytes)

        try:
            tb_bytes = protocol.pickle.dumps(tb)
            protocol.pickle.loads(tb_bytes)
        except Exception:
            tb_bytes = protocol.pickle.dumps(tb_text)

        if len(tb_bytes) > MAX_ERROR_LEN:
            tb_serialized = None
        else:
            tb_serialized = protocol.to_serialize(tb_bytes)

        return {
            "status": status,
            "exception": e_serialized,
            "traceback": tb_serialized,
            "exception_text": repr(e),
            "traceback_text": tb_text,
        }

    def clean_exception(
        exception: BaseException | bytes | bytearray | str | None,
        traceback: types.TracebackType | bytes | str | None = None,
        **kwargs: Any,
    ) -> tuple[
        type[BaseException | None], BaseException | None, types.TracebackType | None
    ]:
        """Reraise exception and traceback. Deserialize if necessary

        See Also
        --------
        error_message : create and serialize errors into message
        """
        if isinstance(exception, (bytes, bytearray)):
            try:
                exception = protocol.pickle.loads(exception)
            except Exception:
                exception = Exception(exception)
        elif isinstance(exception, str):
            exception = Exception(exception)

        if isinstance(traceback, bytes):
            try:
                traceback = protocol.pickle.loads(traceback)
            except (TypeError, AttributeError):
                traceback = None
        elif isinstance(traceback, str):
            traceback = None  # happens if the traceback failed serializing

        assert isinstance(exception, BaseException) or exception is None
        assert isinstance(traceback, types.TracebackType) or traceback is None
        return type(exception), exception, traceback