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 99 100
