distributed breaks with msgpack 1.0.0rc1

[sk1p]

Just for information, distributed breaks with the 1.0.0 release candidate of msgpack. To reproduce:

1. pip install distributed 'msgpack==1.0.0rc1'
2. start a local dask cluster
3. connect client and call Client.run(some_function)

In [2]: Client("tcp://...:8786")                                     
Out[2]: <Client: 'tcp://...:8786' processes=1 threads=8, memory=16.46 GB>

In [3]: c = Client("tcp://...:8786")                                 

In [4]: c.run(lambda: "meh")                                                    
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-4-5ff942d48f6b> in <module>
----> 1 c.run(lambda: "meh")

~/.virtualenvs/ddtest/lib/python3.7/site-packages/distributed/client.py in run(self, function, *args, **kwargs)
   2384         >>> c.run(print_state, wait=False)  # doctest: +SKIP
   2385         """
-> 2386         return self.sync(self._run, function, *args, **kwargs)
   2387 
   2388     def run_coroutine(self, function, *args, **kwargs):

~/.virtualenvs/ddtest/lib/python3.7/site-packages/distributed/client.py in sync(self, func, asynchronous, callback_timeout, *args, **kwargs)
    765         else:
    766             return sync(
--> 767                 self.loop, func, *args, callback_timeout=callback_timeout, **kwargs
    768             )
    769 

~/.virtualenvs/ddtest/lib/python3.7/site-packages/distributed/utils.py in sync(loop, func, callback_timeout, *args, **kwargs)
    343     if error[0]:
    344         typ, exc, tb = error[0]
--> 345         raise exc.with_traceback(tb)
    346     else:
    347         return result[0]

~/.virtualenvs/ddtest/lib/python3.7/site-packages/distributed/utils.py in f()
    327             if callback_timeout is not None:
    328                 future = asyncio.wait_for(future, callback_timeout)
--> 329             result[0] = yield future
    330         except Exception as exc:
    331             error[0] = sys.exc_info()

~/.virtualenvs/ddtest/lib/python3.7/site-packages/tornado/gen.py in run(self)
    733 
    734                     try:
--> 735                         value = future.result()
    736                     except Exception:
    737                         exc_info = sys.exc_info()

~/.virtualenvs/ddtest/lib/python3.7/site-packages/distributed/client.py in _run(self, function, nanny, workers, wait, *args, **kwargs)
   2313             ),
   2314             workers=workers,
-> 2315             nanny=nanny,
   2316         )
   2317         results = {}

~/.virtualenvs/ddtest/lib/python3.7/site-packages/distributed/core.py in send_recv_from_rpc(**kwargs)
    755             name, comm.name = comm.name, "ConnectionPool." + key
    756             try:
--> 757                 result = await send_recv(comm=comm, op=key, **kwargs)
    758             finally:
    759                 self.pool.reuse(self.addr, comm)

~/.virtualenvs/ddtest/lib/python3.7/site-packages/distributed/core.py in send_recv(comm, reply, serializers, deserializers, **kwargs)
    538         await comm.write(msg, serializers=serializers, on_error="raise")
    539         if reply:
--> 540             response = await comm.read(deserializers=deserializers)
    541         else:
    542             response = None

~/.virtualenvs/ddtest/lib/python3.7/site-packages/distributed/comm/tcp.py in read(self, deserializers)
    210             try:
    211                 msg = await from_frames(
--> 212                     frames, deserialize=self.deserialize, deserializers=deserializers
    213                 )
    214             except EOFError:

~/.virtualenvs/ddtest/lib/python3.7/site-packages/distributed/comm/utils.py in from_frames(frames, deserialize, deserializers)
     67         res = await offload(_from_frames)
     68     else:
---> 69         res = _from_frames()
     70 
     71     return res

~/.virtualenvs/ddtest/lib/python3.7/site-packages/distributed/comm/utils.py in _from_frames()
     53         try:
     54             return protocol.loads(
---> 55                 frames, deserialize=deserialize, deserializers=deserializers
     56             )
     57         except EOFError:

~/.virtualenvs/ddtest/lib/python3.7/site-packages/distributed/protocol/core.py in loads(frames, deserialize, deserializers)
    104 
    105         header = frames.pop()
--> 106         header = msgpack.loads(header, use_list=False, **msgpack_opts)
    107         keys = header["keys"]
    108         headers = header["headers"]

msgpack/_unpacker.pyx in msgpack._cmsgpack.unpackb()

ValueError: tuple is not allowed for map key

distributed.protocol.core - CRITICAL - Failed to deserialize
Traceback (most recent call last):
  File "/home/alex/.virtualenvs/ddtest/lib/python3.7/site-packages/distributed/protocol/core.py", line 106, in loads
    header = msgpack.loads(header, use_list=False, **msgpack_opts)
  File "msgpack/_unpacker.pyx", line 195, in msgpack._cmsgpack.unpackb
ValueError: tuple is not allowed for map key

cc @Brow71189

[mrocklin]

Thank you for raising this @sk1p . Indeed, that seems like something that we should resolve quickly.

[sk1p]

Update: version 1.0.0 was just released.

[jrbourbeau]

Thanks for giving us a heads up on the changes in msgpack @sk1p! I've opened up #3494 with a proposed fix