Importer should warn for __main__ imports lacking execution guard

[RedheatWei]

Background:
I want sync files with mitogen, I think I can read file content as a variable send to other machine, this is my test code. But it has error,I don't know why .
And have some other programme to sync files?
Thanks!

Environment:Python 3.6.5rc1, macOS High Sierra 10.13.6, mitogen 0.2.2

#!/usr/bin/env python
#
'''
file t1.py
'''
import mitogen.master
import mitogen.select
import subprocess
import logging
import mitogen.utils
import time
import os

def read_local():
    with open('/Users/Redheat/Documents/code/easou/ops/manage.py','rb') as f:
        return f.read()


def main(router):
    local = router.local(debug=True)
    file_content = local.call(read_local)
    hostnames = ['192.168.101.25', '192.168.101.27', '192.168.101.29']
    remote_hosts = [router.ssh(hostname=hostname, username='root', check_host_keys='accept') for hostname in hostnames]
    rc = [remote_host.call(write_local,file_content) for remote_host in remote_hosts]
    print('Command return code was:', rc)

def write_local(file_content):
    with open('/tmp/ops.sql', 'wb') as f:
        f.write(file_content)


logging.basicConfig(level=logging.INFO)
mitogen.utils.run_with_router(main)

[Redheat@Redheat-Mac/ops]$python3 t1.py 
Traceback (most recent call last):
  File "t1.py", line 30, in <module>
    mitogen.utils.run_with_router(main)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/mitogen/utils.py", line 100, in run_with_router
    return func(router, *args, **kwargs)
  File "t1.py", line 18, in main
    file_content = local.call(read_local)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/mitogen/parent.py", line 1027, in call
    return receiver.get().unpickle(throw_dead=False)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/mitogen/core.py", line 487, in unpickle
    raise obj
mitogen.core.CallError: builtins.AttributeError: 'Router' object has no attribute 'importer'
  File "<stdin>", line 2049, in _dispatch_calls
  File "<stdin>", line 2033, in _dispatch_one
  File "<stdin>", line 367, in import_module
  File "<frozen importlib._bootstrap>", line 971, in _find_and_load
  File "<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 656, in _load_unlocked
  File "<frozen importlib._bootstrap>", line 626, in _load_backward_compatible
  File "<stdin>", line 811, in load_module
  File "master:t1.py", line 30, in <module>
    mitogen.utils.run_with_router(main)
  File "master:/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/mitogen/utils.py", line 100, in run_with_router
    return func(router, *args, **kwargs)
  File "master:t1.py", line 17, in main
    local = router.local(debug=True)
  File "master:/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/mitogen/parent.py", line 1286, in local
    return self.connect(u'local', **kwargs)
  File "master:/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/mitogen/parent.py", line 1256, in connect
    return self._connect(klass, name=name, **kwargs)
  File "master:/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/mitogen/parent.py", line 1239, in _connect
    stream.connect()
  File "master:/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/mitogen/parent.py", line 958, in connect
    self.pid, fd, extra_fd = self.start_child()
  File "master:/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/mitogen/parent.py", line 948, in start_child
    args = self.get_boot_command()
  File "master:/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/mitogen/parent.py", line 903, in get_boot_command
    preamble_compressed = self.get_preamble()
  File "master:/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/mitogen/parent.py", line 939, in get_preamble
    self.get_econtext_config(),
  File "master:/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/mitogen/parent.py", line 930, in get_econtext_config
    'whitelist': self._router.get_module_whitelist(),
  File "master:/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/mitogen/parent.py", line 1214, in get_module_whitelist
    return self.importer.whitelist

[dw]

Wrap the last 2 lines of your script in if __name__ == "__main__" :) The problem is your script starts re-executing on the child the moment it is imported, and the child only has the minimum code loaded at that point.

This is still a bug - the library should have warned you about an import of __main__ where it could not detect an execution guard.

Thanks for reporting!

[RedheatWei]

@dw
Thank you, dw.

[dw]

This is now on the master branch and will make it into the next release. To be updated when a new release is made, subscribe to https://networkgenomics.com/mail/mitogen-announce/

Thanks for reporting this!