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# Copyright (C) 2011 Canonical Ltd
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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"""Signal handling for the smart server code."""
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from __future__ import absolute_import
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from bzrlib import trace
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# I'm pretty sure this has to be global, since signal handling is per-process.
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# TODO: Using a dict means that the order of calls is unordered. We could use a
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# list and then do something like LIFO ordering. A dict was chosen so
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# that you could have a key to easily remove your entry. However, you
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# could just use the callable itself as the indexed part, and even in
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# large cases, we shouldn't have more than 100 or so callbacks
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def _sighup_handler(signal_number, interrupted_frame):
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"""This is the actual function that is registered for handling SIGHUP.
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It will call out to all the registered functions, letting them know that a
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graceful termination has been requested.
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if _on_sighup is None:
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trace.mutter('Caught SIGHUP, sending graceful shutdown requests.')
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for ref in _on_sighup.valuerefs():
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except KeyboardInterrupt:
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trace.mutter('Error occurred while running SIGHUP handlers:')
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trace.log_exception_quietly()
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def install_sighup_handler():
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"""Setup a handler for the SIGHUP signal."""
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if getattr(signal, "SIGHUP", None) is None:
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# If we can't install SIGHUP, there is no reason (yet) to do graceful
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old_signal = signal.signal(signal.SIGHUP, _sighup_handler)
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old_dict = _setup_on_hangup_dict()
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return old_signal, old_dict
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def _setup_on_hangup_dict():
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"""Create something for _on_sighup.
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This is done when we install the sighup handler, and for tests that want to
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test the functionality. If this hasn'nt been called, then
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register_on_hangup is a no-op. As is unregister_on_hangup.
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_on_sighup = weakref.WeakValueDictionary()
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def restore_sighup_handler(orig):
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"""Pass in the returned value from install_sighup_handler to reset."""
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old_signal, old_dict = orig
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if old_signal is not None:
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signal.signal(signal.SIGHUP, old_signal)
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# TODO: Should these be single-use callables? Meaning that once we've triggered
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# SIGHUP and called them, they should auto-remove themselves? I don't
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# think so. Callers need to clean up during shutdown anyway, so that we
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# don't end up with lots of garbage in the _on_sighup dict. On the other
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# hand, we made _on_sighup a WeakValueDictionary in case cleanups didn't
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# get fired properly. Maybe we just assume we don't have to do it?
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def register_on_hangup(identifier, a_callable):
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"""Register for us to call a_callable as part of a graceful shutdown."""
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if _on_sighup is None:
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_on_sighup[identifier] = a_callable
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def unregister_on_hangup(identifier):
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"""Remove a callback from being called during sighup."""
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if _on_sighup is None:
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del _on_sighup[identifier]
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except KeyboardInterrupt:
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# This usually runs as a tear-down step. So we don't want to propagate
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trace.mutter('Error occurred during unregister_on_hangup:')
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trace.log_exception_quietly()
added
removed
bzrlib/smart/signals.py
