What happened

Failed to create the local cluster. I got a different cases of error when I put the extra worker argument or not.

Case 1: without worker parameter

When I run following code:

from dask.distributed import LocalCluster
cluster = LocalCluster()

Three kinds of error string are shown and then failed to create the local cluster.

Error type A

tornado.application - ERROR - Exception in callback <bound method Nanny.memory_monitor of <Nanny: None, threads: 4>>
Traceback (most recent call last):
  File "/home/idblab/anaconda3/envs/jupyter/lib/python3.7/site-packages/tornado/ioloop.py", line 907, in _run
    return self.callback()
  File "/home/idblab/anaconda3/envs/jupyter/lib/python3.7/site-packages/distributed/nanny.py", line 414, in memory_monitor
    process = self.process.process
AttributeError: 'NoneType' object has no attribute 'process'

Error type B

tornado.application - ERROR - Exception in callback functools.partial(<bound method IOLoop._discard_future_result of <zmq.eventloop.ioloop.ZMQIOLoop object at 0x7fb340c0df90>>, <Task finished coro=<Nanny._on_exit() done, defined at /home/idblab/anaconda3/envs/jupyter/lib/python3.7/site-packages/distributed/nanny.py:440> exception=TypeError('addresses should be strings or tuples, got None')>)
Traceback (most recent call last):
  File "/home/idblab/anaconda3/envs/jupyter/lib/python3.7/site-packages/tornado/ioloop.py", line 743, in _run_callback
    ret = callback()
  File "/home/idblab/anaconda3/envs/jupyter/lib/python3.7/site-packages/tornado/ioloop.py", line 767, in _discard_future_result
    future.result()
  File "/home/idblab/anaconda3/envs/jupyter/lib/python3.7/site-packages/distributed/nanny.py", line 443, in _on_exit
    await self.scheduler.unregister(address=self.worker_address)
  File "/home/idblab/anaconda3/envs/jupyter/lib/python3.7/site-packages/distributed/core.py", line 861, in send_recv_from_rpc
    result = await send_recv(comm=comm, op=key, **kwargs)
  File "/home/idblab/anaconda3/envs/jupyter/lib/python3.7/site-packages/distributed/core.py", line 660, in send_recv
    raise exc.with_traceback(tb)
  File "/home/idblab/anaconda3/envs/jupyter/lib/python3.7/site-packages/distributed/core.py", line 513, in handle_comm
    result = await result
  File "/home/idblab/anaconda3/envs/jupyter/lib/python3.7/site-packages/distributed/scheduler.py", line 2208, in remove_worker
    address = self.coerce_address(address)
  File "/home/idblab/anaconda3/envs/jupyter/lib/python3.7/site-packages/distributed/scheduler.py", line 4946, in coerce_address
    raise TypeError("addresses should be strings or tuples, got %r" % (addr,))
TypeError: addresses should be strings or tuples, got None

Error type C

distributed.utils - ERROR - addresses should be strings or tuples, got None
Traceback (most recent call last):
  File "/home/idblab/anaconda3/envs/jupyter/lib/python3.7/site-packages/distributed/utils.py", line 656, in log_errors
    yield
  File "/home/idblab/anaconda3/envs/jupyter/lib/python3.7/site-packages/distributed/scheduler.py", line 2208, in remove_worker
    address = self.coerce_address(address)
  File "/home/idblab/anaconda3/envs/jupyter/lib/python3.7/site-packages/distributed/scheduler.py", line 4946, in coerce_address
    raise TypeError("addresses should be strings or tuples, got %r" % (addr,))
TypeError: addresses should be strings or tuples, got None

Error type D

distributed.core - ERROR - addresses should be strings or tuples, got None
Traceback (most recent call last):
  File "/home/idblab/anaconda3/envs/jupyter/lib/python3.7/site-packages/distributed/core.py", line 513, in handle_comm
    result = await result
  File "/home/idblab/anaconda3/envs/jupyter/lib/python3.7/site-packages/distributed/scheduler.py", line 2208, in remove_worker
    address = self.coerce_address(address)
  File "/home/idblab/anaconda3/envs/jupyter/lib/python3.7/site-packages/distributed/scheduler.py", line 4946, in coerce_address
    raise TypeError("addresses should be strings or tuples, got %r" % (addr,))
TypeError: addresses should be strings or tuples, got None

Full logs

http://paste.debian.net/1158552/

Case 2: with worker parameter

When I put extra worker parameter local_directory into LocalCluster() like following code:

from dask.distributed import LocalCluster
cluster = LocalCluster(local_directory="/tmp/dask-worker-space")

Now only the Error type A above shown and then failed to create the local cluster.

Full logs

http://paste.debian.net/1158551/

What you expected to happen

• This is my first time for using Dask. I couldn’t load Dask at first and never before, so I don’t know how the expected behaviour.

Minimal Complete Verifiable Example

Case 1: without worker parameter

from dask.distributed import LocalCluster
cluster = LocalCluster()

Case 2: with worker parameter

from dask.distributed import LocalCluster
cluster = LocalCluster(local_directory="/tmp/dask-worker-space")

Anything else we need to know?

• Potential related issue: #3955 (same with Error type A)

Environment

• Dask version: 2.20.0

  (jupyter) idblab@debian-20200402:~$ conda list
  # packages in environment at /home/idblab/anaconda3/envs/jupyter:
  #
  # Name                    Version                   Build  Channel
  dask                      2.20.0                     py_0  
  dask-core                 2.20.0                     py_0
  distributed               2.20.0                   py37_0
  

• Python version: Python 3.7.7
• Operating System: Linux debian-20200402 5.7.0-2-amd64 #1 SMP Debian 5.7.10-1 (2020-07-26) x86_64 GNU/Linux
• Install method (conda, pip, source): conda install dask distributed -c conda-forge