88 lines
2.7 KiB
Python
88 lines
2.7 KiB
Python
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# -*- test-case-name: twisted.python.test.test_systemd -*-
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# Copyright (c) Twisted Matrix Laboratories.
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# See LICENSE for details.
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"""
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Integration with systemd.
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Currently only the minimum APIs necessary for using systemd's socket activation
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feature are supported.
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"""
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__all__ = ['ListenFDs']
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from os import getpid
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class ListenFDs(object):
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"""
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L{ListenFDs} provides access to file descriptors inherited from systemd.
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Typically L{ListenFDs.fromEnvironment} should be used to construct a new
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instance of L{ListenFDs}.
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@cvar _START: File descriptors inherited from systemd are always
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consecutively numbered, with a fixed lowest "starting" descriptor. This
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gives the default starting descriptor. Since this must agree with the
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value systemd is using, it typically should not be overridden.
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@type _START: C{int}
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@ivar _descriptors: A C{list} of C{int} giving the descriptors which were
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inherited.
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"""
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_START = 3
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def __init__(self, descriptors):
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"""
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@param descriptors: The descriptors which will be returned from calls to
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C{inheritedDescriptors}.
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"""
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self._descriptors = descriptors
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@classmethod
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def fromEnvironment(cls, environ=None, start=None):
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"""
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@param environ: A dictionary-like object to inspect to discover
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inherited descriptors. By default, C{None}, indicating that the
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real process environment should be inspected. The default is
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suitable for typical usage.
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@param start: An integer giving the lowest value of an inherited
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descriptor systemd will give us. By default, C{None}, indicating
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the known correct (that is, in agreement with systemd) value will be
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used. The default is suitable for typical usage.
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@return: A new instance of C{cls} which can be used to look up the
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descriptors which have been inherited.
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"""
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if environ is None:
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from os import environ
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if start is None:
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start = cls._START
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descriptors = []
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try:
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pid = int(environ['LISTEN_PID'])
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except (KeyError, ValueError):
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pass
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else:
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if pid == getpid():
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try:
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count = int(environ['LISTEN_FDS'])
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except (KeyError, ValueError):
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pass
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else:
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descriptors = range(start, start + count)
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del environ['LISTEN_PID'], environ['LISTEN_FDS']
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return cls(descriptors)
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def inheritedDescriptors(self):
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"""
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@return: The configured list of descriptors.
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"""
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return list(self._descriptors)
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