tools/telemetry/third_party/gsutilz/gslib/sig_handling.py

   1 # -*- coding: utf-8 -*-
   2 # Copyright 2015 Google Inc. All Rights Reserved.
   3 #
   4 # Licensed under the Apache License, Version 2.0 (the "License");
   5 # you may not use this file except in compliance with the License.
   6 # You may obtain a copy of the License at
   7 #
   8 #     http://www.apache.org/licenses/LICENSE-2.0
   9 #
  10 # Unless required by applicable law or agreed to in writing, software
  11 # distributed under the License is distributed on an "AS IS" BASIS,
  12 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13 # See the License for the specific language governing permissions and
  14 # limitations under the License.
  15 """Signal handling functions."""
  16
  17 from __future__ import absolute_import
  18
  19 import signal
  20 from gslib.util import IS_WINDOWS
  21
  22
  23 # Maps from signal_num to list of signal handlers to call.
  24 _non_final_signal_handlers = {}
  25 # Maps from signal_num to the final signal handler (if any) that should be
  26 # called for that signal.
  27 _final_signal_handlers = {}
  28
  29
  30 def RegisterSignalHandler(signal_num, handler, is_final_handler=False):
  31   """Registers a handler for signal signal_num.
  32
  33   Unlike calling signal.signal():
  34     - This function can be called from any thread (and will cause the handler to
  35       be run by the main thread when the signal is received).
  36     - Handlers are cumulative: When a given signal is received, all registered
  37       handlers will be executed (with the exception that only the last handler
  38       to register with is_final_handler=True will be called).
  39
  40   Handlers should make no ordering assumptions, other than that the last handler
  41   to register with is_final_handler=True will be called after all the other
  42   handlers.
  43
  44   Args:
  45     signal_num: The signal number with which to associate handler.
  46     handler: The handler.
  47     is_final_handler: Bool indicator whether handler should be called last among
  48                       all the handlers for this signal_num. The last handler to
  49                       register this way survives; other handlers registered with
  50                       is_final_handler=True will not be called when the signal
  51                       is received.
  52   Raises:
  53     RuntimeError: if attempt is made to register a signal_num not in
  54         GetCaughtSignals.
  55   """
  56   if signal_num not in GetCaughtSignals():
  57     raise RuntimeError('Attempt to register handler (%s) for signal %d, which '
  58                        'is not in GetCaughtSignals' % (handler, signal_num))
  59   if is_final_handler:
  60     _final_signal_handlers[signal_num] = handler
  61   else:
  62     _non_final_signal_handlers[signal_num].append(handler)
  63
  64
  65 def _SignalHandler(signal_num, cur_stack_frame):
  66   """Global signal handler.
  67
  68   When a signal is caught we execute each registered handler for that signal.
  69
  70   Args:
  71     signal_num: Signal that was caught.
  72     cur_stack_frame: Unused.
  73   """
  74   if signal_num in _non_final_signal_handlers:
  75     for handler in _non_final_signal_handlers[signal_num]:
  76       handler(signal_num, cur_stack_frame)
  77   if signal_num in _final_signal_handlers:
  78     _final_signal_handlers[signal_num](signal_num, cur_stack_frame)
  79
  80
  81 def InitializeSignalHandling():
  82   """Initializes global signal handling.
  83
  84   Sets up global signal handler for each signal we handle.
  85   """
  86   for signal_num in GetCaughtSignals():
  87     _non_final_signal_handlers[signal_num] = []
  88     # Make main signal handler catch the signal.
  89     signal.signal(signal_num, _SignalHandler)
  90
  91
  92 def GetCaughtSignals():
  93   """Returns terminating signals that can be caught on this OS platform."""
  94   signals = [signal.SIGINT, signal.SIGTERM]
  95   if not IS_WINDOWS:
  96     # Windows doesn't have SIGQUIT.
  97     signals.append(signal.SIGQUIT)
  98   return signals
  99