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mitogen: Prevent hung bootstrap processes, add 5 second timeout to first stage #1349

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mitogen: Prevent hung bootstrap processes, add 5 second timeout to first stage #1349

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82a0efc
mitogen: Allow line comments in first stage, strip them.
moreati Oct 30, 2025
03a0a15
mitogen: Kill (hung) bootstrap processes after 5 second timeout
moreati Nov 27, 2025
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3 changes: 3 additions & 0 deletions docs/changelog.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,9 @@ To avail of fixes in an unreleased version, please download a ZIP file
In progress (unreleased)
------------------------

* :gh:issue:`1266` :mod:`mitogen`: Prevent hung bootstrap processes, add 5
second timeout to first stage


v0.3.34 (2025-11-27)
--------------------
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13 changes: 9 additions & 4 deletions mitogen/parent.py
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Expand Up @@ -1436,6 +1436,10 @@ def _first_stage():
if os.uname()[0]+os.uname()[2][:2]+sys.version[:3]=='Darwin212.7':os.environ['PYTHON_LAUNCHED_FROM_WRAPPER']='1'
os.environ['ARGV0']=sys.executable
os.execl(sys.executable,sys.executable+'(mitogen:%s)'%sys.argv[2])
# Timeout execution after a few seconds, to prevent hung processes.
# Cause might be closed/reset pipe/stream backing stdin (fd=0);
# or blocking write to interpreter stdin (fd=W, fd=w).
signal.alarm(5)
os.write(1,'MITO000\n'.encode())
C=''.encode()
while int(sys.argv[3])-len(C)and select.select([0],[],[]):C+=os.read(0,int(sys.argv[3])-len(C))
Expand Down Expand Up @@ -1463,8 +1467,9 @@ def get_python_argv(self):
return [self.options.python_path]

def get_boot_command(self):
source = inspect.getsource(self._first_stage)
source = textwrap.dedent('\n'.join(source.strip().split('\n')[2:]))
lines = inspect.getsourcelines(self._first_stage)[0][2:]
# Remove line comments, leading indentation, trailing newline
source = textwrap.dedent(''.join(s for s in lines if '#' not in s))[:-1]
source = source.replace(' ', ' ')
compressor = zlib.compressobj(
zlib.Z_BEST_COMPRESSION, zlib.DEFLATED, -zlib.MAX_WBITS,
Expand All @@ -1475,11 +1480,11 @@ def get_boot_command(self):
# Just enough to decode, decompress, and exec the first stage.
# Priorities: wider compatibility, faster startup, shorter length.
# `sys.path=...` for https://github.com/python/cpython/issues/115911.
# `import os,select` here (not stage 1) to save a few bytes overall.
# `import os,...` here (not stage 1) saves a few bytes overall.
return self.get_python_argv() + [
'-c',
'import sys;sys.path=[p for p in sys.path if p];'
'import binascii,os,select,zlib;'
'import binascii,os,select,signal,zlib;'
'exec(zlib.decompress(binascii.a2b_base64(sys.argv[1]),-15))',
encoded.decode(),
self.options.remote_name,
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