text: import asyncio
  from collections import defaultdict, deque
  from functools import partial
  import inspect
  import logging
  import threading
  import traceback
  import uuid
  import weakref
  
  import dask
  import tblib
  from tlz import merge
  from tornado import gen
  from tornado.ioloop import IOLoop
  
  from .comm import (
      connect,
      listen,
      CommClosedError,
      normalize_address,
      unparse_host_port,
      get_address_host_port,
  )
  from .metrics import time
  from . import profile
  from .system_monitor import SystemMonitor
  from .utils import (
      is_coroutine_function,
      get_traceback,
      truncate_exception,
      ignoring,
      shutting_down,
      PeriodicCallback,
      parse_timedelta,
      has_keyword,
      CancelledError,
  )
  from . import protocol
  
  
  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")
  
  
  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}``
  
      """
  
      default_ip = ""
      default_port = 0
  
      def __init__(
          self,
          handlers,
          blocked_handlers=None,
          stream_handlers=None,
          connection_limit=512,
          deserialize=True,
          io_loop=None,
      ):
          self.handlers = {
              "identity": self.identity,
              "connection_stream": self.handle_stream,
          }
          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._comms = {}
          self.deserialize = deserialize
          self.monitor = SystemMonitor()
          self.counters = None
          self.digests = None
          self.events = None
          self.event_counts = None
          self._ongoing_coroutines = weakref.WeakSet()
          self._event_finished = asyncio.Event()
  
          self.listeners = []
          self.io_loop = io_loop or IOLoop.current()
          self.loop = self.io_loop
  
          if not hasattr(self.io_loop, "profile"):
              ref = weakref.ref(self.io_loop)
  
              if hasattr(self.io_loop, "asyncio_loop"):
  
                  def stop():
                      loop = ref()
                      return loop is None or loop.asyncio_loop.is_closed()
  
              else:
  
                  def stop():
                      loop = ref()
                      return loop is None or loop._closing
  
              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,
              )
  
          # Statistics counters for various events
          with ignoring(ImportError):
              from .counter import Digest
  
              self.digests = defaultdict(partial(Digest, loop=self.io_loop))
  
          from .counter import Counter
  
          self.counters = defaultdict(partial(Counter, loop=self.io_loop))
          self.events = defaultdict(lambda: deque(maxlen=10000))
          self.event_counts = defaultdict(lambda: 0)
  
          self.periodic_callbacks = dict()
  
          pc = PeriodicCallback(self.monitor.update, 500, io_loop=self.io_loop)
          self.periodic_callbacks["monitor"] = pc
  
          self._last_tick = time()
          pc = PeriodicCallback(
              self._measure_tick,
              parse_timedelta(
                  dask.config.get("distributed.admin.tick.interval"), default="ms"
              )
              * 1000,
              io_loop=self.io_loop,
          )
          self.periodic_callbacks["tick"] = pc
  
          self.thread_id = 0
  
          def set_thread_ident():
              self.thread_id = threading.get_ident()
  
          self.io_loop.add_callback(set_thread_ident)
  
          self.__stopped = False
  
      async def finished(self):
          """ Wait until the server has finished """
          await self._event_finished.wait()
  
      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 on the IOLoop.
          """
          self._last_tick = time()
  
          def start_pcs():
              for pc in self.periodic_callbacks.values():
                  if not pc.is_running():
                      pc.start()
  
          self.io_loop.add_callback(start_pcs)
  
      def stop(self):
          if not self.__stopped:
              self.__stopped = True
              for listener in self.listeners:
                  # Delay closing the server socket until the next IO loop tick.
                  # Otherwise race conditions can appear if an event handler
                  # for an accept() call is already scheduled by the IO loop,
                  # raising EBADF.
                  # The demonstrator for this is Worker.terminate(), which
                  # closes the server socket in response to an incoming message.
                  # See https://github.com/tornadoweb/tornado/issues/2069
                  self.io_loop.add_callback(listener.stop)
  
      @property
      def listener(self):
          if self.listeners:
              return self.listeners[0]
          else:
              return None
  
      def _measure_tick(self):
          now = time()
          diff = now - self._last_tick
          self._last_tick = now
          if diff > 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__,
                  diff,
              )
          if self.digests is not None:
              self.digests["tick-duration"].add(diff)
  
      def log_event(self, name, msg):
          msg["time"] = time()
          if isinstance(name, list):
              for n in name:
                  self.events[n].append(msg)
                  self.event_counts[n] += 1
          else:
              self.events[name].append(msg)
              self.event_counts[name] += 1
  
      @property
      def address(self):
          """
          The address this Server can be contacted on.
          """
          if not self._address:
              if self.listener is None:
                  raise ValueError("cannot get address of non-running Server")
              self._address = self.listener.contact_address
          return self._address
  
      @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 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._port = get_address_host_port(self.address)
          return self._port
  
      def identity(self, comm=None):
          return {"type": type(self).__name__, "id": self.id}
  
      async def listen(self, port_or_addr=None, listen_args=None):
          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,
              connection_args=listen_args,
          )
          self.listeners.append(listener)
  
      async def handle_comm(self, comm, shutting_down=shutting_down):
          """ 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
          try:
              while True:
                  try:
                      msg = await comm.read()
                      logger.debug("Message from %r: %s", address, msg)
                  except EnvironmentError as e:
                      if not shutting_down():
                          logger.debug(
                              "Lost connection to %r while reading message: %s."
                              " Last operation: %s",
                              address,
                              e,
                              op,
                          )
                      break
                  except Exception as e:
                      logger.exception(e)
                      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:
                      raise ValueError(
                          "Received unexpected message without 'op' key: " + str(msg)
                      )
                  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:
                          result = handler(comm, **msg)
                          if inspect.isawaitable(result):
                              result = asyncio.ensure_future(result)
                              self._ongoing_coroutines.add(result)
                              result = await result
                      except (CommClosedError, CancelledError) as e:
                          if self.status == "running":
                              logger.info("Lost connection to %r: %s", address, e)
                          break
                      except Exception as e:
                          logger.exception(e)
                          result = error_message(e, status="uncaught-error")
  
                  if reply and result != "dont-reply":
                      try:
                          await comm.write(result, serializers=serializers)
                      except (EnvironmentError, TypeError) as e:
                          logger.debug(
                              "Lost connection to %r while sending result for op %r: %s",
                              address,
                              op,
                              e,
                          )
                          break
                  msg = result = None
                  if close_desired:
                      await comm.close()
                  if comm.closed():
                      break
  
          finally:
              del self._comms[comm]
              if not shutting_down() 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, extra=None, every_cycle=[]):
          extra = extra or {}
          logger.info("Starting established connection")
  
          io_error = None
          closed = False
          try:
              while not closed:
                  msgs = await comm.read()
                  if not isinstance(msgs, (tuple, list)):
                      msgs = (msgs,)
  
                  if not comm.closed():
                      for msg in msgs:
                          if msg == "OK":  # from close
                              break
                          op = msg.pop("op")
                          if op:
                              if op == "close-stream":
                                  closed = True
                                  break
                              handler = self.stream_handlers[op]
                              if is_coroutine_function(handler):
                                  self.loop.add_callback(handler, **merge(extra, msg))
                              else:
                                  handler(**merge(extra, msg))
                          else:
                              logger.error("odd message %s", msg)
                      await asyncio.sleep(0)
  
                  for func in every_cycle:
                      func()
  
          except (CommClosedError, EnvironmentError) as e:
              io_error = e
          except Exception as e:
              logger.exception(e)
              if LOG_PDB:
                  import pdb
  
                  pdb.set_trace()
              raise
          finally:
              await comm.close()
              assert comm.closed()
  
      @gen.coroutine
      def close(self):
          for pc in self.periodic_callbacks.values():
              pc.stop()
          for listener in self.listeners:
              future = self.listener.stop()
              if inspect.isawaitable(future):
                  yield future
          for i in range(20):  # let comms close naturally for a second
              if not self._comms:
                  break
              else:
                  yield asyncio.sleep(0.05)
          yield [comm.close() for comm in self._comms]  # then forcefully close
          for cb in self._ongoing_coroutines:
              cb.cancel()
          for i in range(10):
              if all(cb.cancelled() for c in self._ongoing_coroutines):
                  break
              else:
                  yield asyncio.sleep(0.01)
  
          self._event_finished.set()
  
  
  def pingpong(comm):
      return b"pong"
  
  
  async def send_recv(comm, reply=True, serializers=None, deserializers=None, **kwargs):
      """ Send and recv with a Comm.
  
      Keyword arguments turn into the message
  
      response = yield send_recv(comm, op='ping', reply=True)
      """
      msg = kwargs
      msg["reply"] = reply
      please_close = kwargs.get("close")
      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 EnvironmentError:
          # On communication errors, we should simply close the communication
          force_close = True
          raise
      finally:
          if please_close:
              await comm.close()
          elif force_close:
              comm.abort()
  
      if isinstance(response, dict) and response.get("status") == "uncaught-error":
          if comm.deserialize:
              typ, exc, tb = clean_exception(**response)
              raise exc.with_traceback(tb)
          else:
              raise Exception(response["text"])
      return response
  
  
  def addr_from_args(addr=None, ip=None, port=None):
      if addr is None:
          addr = (ip, port)
      else:
          assert ip is None and port is None
      if isinstance(addr, tuple):
          addr = unparse_host_port(*addr)
      return normalize_address(addr)
  
  
  class rpc:
      """ Conveniently interact with a remote server
  
      >>> remote = rpc(address)  # doctest: +SKIP
      >>> response = yield 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 = 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 = "running"
          self.deserialize = deserialize
          self.serializers = serializers
          self.deserializers = deserializers if deserializers is not None else serializers
          self.connection_args = connection_args
          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 == "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,
                  connection_args=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 EnvironmentError:
                  comm.abort()
  
          tasks = []
          for comm in list(self.comms):
              if comm and not comm.closed():
                  # IOLoop.current().add_callback(_close_comm, comm)
                  task = asyncio.ensure_future(_close_comm(comm))
                  tasks.append(task)
          for comm in list(self._created):
              if comm and not comm.closed():
                  # IOLoop.current().add_callback(_close_comm, comm)
                  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
              try:
                  comm = await self.live_comm()
                  comm.name = "rpc." + key
                  result = await send_recv(comm=comm, op=key, **kwargs)
              except (RPCClosed, CommClosedError) as e:
                  raise e.__class__(
                      "%s: while trying to call remote method %r" % (e, key)
                  )
  
              self.comms[comm] = True  # mark as open
              return result
  
          return send_recv_from_rpc
  
      def close_rpc(self):
          if self.status != "closed":
              rpc.active.discard(self)
          self.status = "closed"
          return asyncio.gather(*self.close_comms())
  
      def __enter__(self):
          return self
  
      def __exit__(self, *args):
          asyncio.ensure_future(self.close_rpc())
  
      async def __aenter__(self):
          return self
  
      async def __aexit__(self, *args):
          await self.close_rpc()
  
      def __del__(self):
          if self.status != "closed":
              rpc.active.discard(self)
              self.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)
              name, comm.name = comm.name, "ConnectionPool." + key
              try:
                  result = await send_recv(comm=comm, op=key, **kwargs)
              finally:
                  self.pool.reuse(self.addr, comm)
                  comm.name = name
  
              return result
  
          return send_recv_from_rpc
  
      async def close_rpc(self):
          pass
  
      # For compatibility with rpc()
      def __enter__(self):
          return self
  
      def __exit__(self, *args):
          pass
  
      def __repr__(self):
          return "<pooled rpc to %r>" % (self.addr,)
  
  
  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 ...]
  
          >>> info = yield scheduler.identity()
  
      It creates enough comms to satisfy concurrent connections to any
      particular address::
  
          >>> a, b = yield [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 = weakref.WeakSet()
  
      def __init__(
          self,
          limit=512,
          deserialize=True,
          serializers=None,
          deserializers=None,
          connection_args=None,
          timeout=None,
          server=None,
      ):
          self.limit = limit  # Max number of open comms
          # Invariant: len(available) == open - active
          self.available = defaultdict(set)
          # Invariant: len(occupied) == active
          self.occupied = defaultdict(set)
          self.deserialize = deserialize
          self.serializers = serializers
          self.deserializers = deserializers if deserializers is not None else serializers
          self.connection_args = connection_args
          self.timeout = timeout
          self._n_connecting = 0
          self.server = weakref.ref(server) if server else None
          self._created = weakref.WeakSet()
          self._instances.add(self)
  
      def _validate(self):
          """
          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):
          return sum(map(len, self.occupied.values()))
  
      @property
      def open(self):
          return self.active + sum(map(len, self.available.values()))
  
      def __repr__(self):
          return "<ConnectionPool: open=%d, active=%d, connecting=%d>" % (
              self.open,
              self.active,
              self._n_connecting,
          )
  
      def __call__(self, addr=None, ip=None, port=None):
          """ 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):
          async def _():
              await self.start()
              return self
  
          return _().__await__()
  
      async def start(self):
          # Invariant: semaphore._value == limit - open - _n_connecting
          self.semaphore = asyncio.Semaphore(self.limit)
  
      async def connect(self, addr, timeout=None):
          """
          Get a Comm to the given address.  For internal use.
          """
          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()
  
          self._n_connecting += 1
          await self.semaphore.acquire()
  
          try:
              comm = await connect(
                  addr,
                  timeout=timeout or self.timeout,
                  deserialize=self.deserialize,
                  connection_args=self.connection_args,
              )
              comm.name = "ConnectionPool"
              comm._pool = weakref.ref(self)
              self._created.add(comm)
          except Exception:
              self.semaphore.release()
              raise
          finally:
              self._n_connecting -= 1
  
          occupied.add(comm)
  
          return comm
  
      def reuse(self, addr, comm):
          """
          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():
                  self.semaphore.release()
              else:
                  self.available[addr].add(comm)
                  if self.semaphore.locked() and self._n_connecting > 0:
                      self.collect()
  
      def collect(self):
          """
          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,
              self._n_connecting,
          )
          for addr, comms in self.available.items():
              for comm in comms:
                  IOLoop.current().add_callback(comm.close)
                  self.semaphore.release()
              comms.clear()
  
      def remove(self, addr):
          """
          Remove all Comms to a given address.
          """
          logger.info("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()
  
      async def close(self):
          """
          Close all communications
          """
          for d in [self.available, self.occupied]:
              comms = [comm for comms in d.values() for comm in comms]
              await asyncio.gather(
                  *[comm.close() for comm in comms], return_exceptions=True
              )
              for _ in comms:
                  self.semaphore.release()
  
          for comm in self._created:
              IOLoop.current().add_callback(comm.abort)
  
  
  def coerce_to_address(o):
      if isinstance(o, (list, tuple)):
          o = unparse_host_port(*o)
  
      return normalize_address(o)
  
  
  def collect_causes(e):
      causes = []
      while e.__cause__ is not None:
          causes.append(e.__cause__)
          e = e.__cause__
      return causes
  
  
  def error_message(e, status="error"):
      """ 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()
      e2 = truncate_exception(e, MAX_ERROR_LEN)
      try:
          e3 = protocol.pickle.dumps(e2)
          protocol.pickle.loads(e3)
      except Exception:
          e2 = Exception(str(e2))
      e4 = protocol.to_serialize(e2)
      try:
          tb2 = protocol.pickle.dumps(tb)
      except Exception:
          tb = tb2 = "".join(traceback.format_tb(tb))
  
      if len(tb2) > MAX_ERROR_LEN:
          tb_result = None
      else:
          tb_result = protocol.to_serialize(tb)
  
      return {"status": status, "exception": e4, "traceback": tb_result, "text": str(e2)}
  
  
  def clean_exception(exception, traceback, **kwargs):
      """ Reraise exception and traceback. Deserialize if necessary
  
      See Also
      --------
      error_message: create and serialize errors into message
      """
      if isinstance(exception, bytes) or isinstance(exception, 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
      return type(exception), exception, traceback
  