[CASSANDRA-16053] cqlsh COPY functions broken in Python 3.8 on Mac

• Type: Bug
• Status: Resolved
• Priority: Normal
• Resolution: Fixed
• Fix Version/s: 4.0-beta2, 4.0
• Component/s: Tool/cqlsh
• Bug Category: Code - Bug - Unclear Impact
• Severity: Low
• Complexity: Normal
• Discovered By: Unit Test
• Since Version: 4.0-alpha1

Source Control Link

https://github.com/apache/cassandra/commit/0e53379ec945e07c38aed03048ba8f76d42bdd42

Test and Documentation Plan

I ran the repro script from the previous ticket 500+ times, restarting C* (which was said to make it happen more) each time.

• Assignee: Adam Holmberg
• Reporter: Adam Holmberg

Authors

Adam Holmberg

Reviewers

Brandon Williams, Ekaterina Dimitrova

• Created: 17/Aug/20 19:09
• Updated: 20/Aug/20 21:01
• Resolved: 20/Aug/20 20:05

Description

aholmberg-rmbp16:cassandra adamholmberg$ pyenv shell
3.8.2
aholmberg-rmbp16:cassandra adamholmberg$ bin/cqlsh --debug
Using CQL driver: <module 'cassandra' from '/Users/adamholmberg/code/cassandra/bin/../lib/cassandra-driver-internal-only-3.23.0.post0-1a184b99.zip/cassandra-driver-3.23.0.post0-1a184b99/cassandra/__init__.py'>
Using connect timeout: 5 seconds
Using 'utf-8' encoding
Using ssl: False
Connected to Test Cluster at 127.0.0.1:9042.
[cqlsh 5.0.1 | Cassandra 4.0-beta2-SNAPSHOT | CQL spec 3.4.5 | Native protocol v4]
Use HELP for help.
cqlsh> copy test.testcopyto to 'asdf';
Detected 12 core(s)
Using 11 child processes

Starting copy of test.testcopyto with columns [a, b, c, d].
Traceback (most recent call last):
  File "/Users/adamholmberg/code/cassandra/bin/cqlsh.py", line 937, in onecmd
    self.handle_statement(st, statementtext)
  File "/Users/adamholmberg/code/cassandra/bin/cqlsh.py", line 974, in handle_statement
    return custom_handler(parsed)
  File "/Users/adamholmberg/code/cassandra/bin/cqlsh.py", line 1563, in do_copy
    task.run()
  File "/Users/adamholmberg/code/cassandra/bin/../pylib/cqlshlib/copyutil.py", line 669, in run
    self.start_processes()
  File "/Users/adamholmberg/code/cassandra/bin/../pylib/cqlshlib/copyutil.py", line 471, in start_processes
    process.start()
  File "/Users/adamholmberg/.pyenv/versions/3.8.2/lib/python3.8/multiprocessing/process.py", line 121, in start
    self._popen = self._Popen(self)
  File "/Users/adamholmberg/.pyenv/versions/3.8.2/lib/python3.8/multiprocessing/context.py", line 224, in _Popen
    return _default_context.get_context().Process._Popen(process_obj)
  File "/Users/adamholmberg/.pyenv/versions/3.8.2/lib/python3.8/multiprocessing/context.py", line 283, in _Popen
    return Popen(process_obj)
  File "/Users/adamholmberg/.pyenv/versions/3.8.2/lib/python3.8/multiprocessing/popen_spawn_posix.py", line 32, in __init__
    super().__init__(process_obj)
  File "/Users/adamholmberg/.pyenv/versions/3.8.2/lib/python3.8/multiprocessing/popen_fork.py", line 19, in __init__
    self._launch(process_obj)
  File "/Users/adamholmberg/.pyenv/versions/3.8.2/lib/python3.8/multiprocessing/popen_spawn_posix.py", line 47, in _launch
    reduction.dump(process_obj, fp)
  File "/Users/adamholmberg/.pyenv/versions/3.8.2/lib/python3.8/multiprocessing/reduction.py", line 60, in dump
    ForkingPickler(file, protocol).dump(obj)
TypeError: cannot pickle '_thread.lock' object
cqlsh>

multiprocessing uses a different default start method on Mac, and pickling fails trying to serialize the Cluster object.
https://github.com/python/cpython/blob/db098bc1f05bd0773943e59f83489f05f28dedf8/Lib/multiprocessing/context.py#L313-L318
https://bugs.python.org/issue33725

Issue Links

• relates to: CASSANDRA-11749 CQLSH gets SSL exception following a COPY FROM