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| 1 # Copyright 2014 Google Inc. All rights reserved. | |
| 2 # | |
| 3 # Licensed under the Apache License, Version 2.0 (the "License"); | |
| 4 # you may not use this file except in compliance with the License. | |
| 5 # You may obtain a copy of the License at | |
| 6 # | |
| 7 # http://www.apache.org/licenses/LICENSE-2.0 | |
| 8 # | |
| 9 # Unless required by applicable law or agreed to in writing, software | |
| 10 # distributed under the License is distributed on an "AS IS" BASIS, | |
| 11 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |
| 12 # See the License for the specific language governing permissions and | |
| 13 # limitations under the License. | |
| 14 | |
| 15 """Locked file interface that should work on Unix and Windows pythons. | |
| 16 | |
| 17 This module first tries to use fcntl locking to ensure serialized access | |
| 18 to a file, then falls back on a lock file if that is unavialable. | |
| 19 | |
| 20 Usage:: | |
| 21 | |
| 22 f = LockedFile('filename', 'r+b', 'rb') | |
| 23 f.open_and_lock() | |
| 24 if f.is_locked(): | |
| 25 print('Acquired filename with r+b mode') | |
| 26 f.file_handle().write('locked data') | |
| 27 else: | |
| 28 print('Acquired filename with rb mode') | |
| 29 f.unlock_and_close() | |
| 30 | |
| 31 """ | |
| 32 | |
| 33 from __future__ import print_function | |
| 34 | |
| 35 import errno | |
| 36 import logging | |
| 37 import os | |
| 38 import time | |
| 39 | |
| 40 from oauth2client import util | |
| 41 | |
| 42 | |
| 43 __author__ = 'cache@google.com (David T McWherter)' | |
| 44 | |
| 45 logger = logging.getLogger(__name__) | |
| 46 | |
| 47 | |
| 48 class CredentialsFileSymbolicLinkError(Exception): | |
| 49 """Credentials files must not be symbolic links.""" | |
| 50 | |
| 51 | |
| 52 class AlreadyLockedException(Exception): | |
| 53 """Trying to lock a file that has already been locked by the LockedFile.""" | |
| 54 pass | |
| 55 | |
| 56 | |
| 57 def validate_file(filename): | |
| 58 if os.path.islink(filename): | |
| 59 raise CredentialsFileSymbolicLinkError( | |
| 60 'File: %s is a symbolic link.' % filename) | |
| 61 | |
| 62 | |
| 63 class _Opener(object): | |
| 64 """Base class for different locking primitives.""" | |
| 65 | |
| 66 def __init__(self, filename, mode, fallback_mode): | |
| 67 """Create an Opener. | |
| 68 | |
| 69 Args: | |
| 70 filename: string, The pathname of the file. | |
| 71 mode: string, The preferred mode to access the file with. | |
| 72 fallback_mode: string, The mode to use if locking fails. | |
| 73 """ | |
| 74 self._locked = False | |
| 75 self._filename = filename | |
| 76 self._mode = mode | |
| 77 self._fallback_mode = fallback_mode | |
| 78 self._fh = None | |
| 79 self._lock_fd = None | |
| 80 | |
| 81 def is_locked(self): | |
| 82 """Was the file locked.""" | |
| 83 return self._locked | |
| 84 | |
| 85 def file_handle(self): | |
| 86 """The file handle to the file. Valid only after opened.""" | |
| 87 return self._fh | |
| 88 | |
| 89 def filename(self): | |
| 90 """The filename that is being locked.""" | |
| 91 return self._filename | |
| 92 | |
| 93 def open_and_lock(self, timeout, delay): | |
| 94 """Open the file and lock it. | |
| 95 | |
| 96 Args: | |
| 97 timeout: float, How long to try to lock for. | |
| 98 delay: float, How long to wait between retries. | |
| 99 """ | |
| 100 pass | |
| 101 | |
| 102 def unlock_and_close(self): | |
| 103 """Unlock and close the file.""" | |
| 104 pass | |
| 105 | |
| 106 | |
| 107 class _PosixOpener(_Opener): | |
| 108 """Lock files using Posix advisory lock files.""" | |
| 109 | |
| 110 def open_and_lock(self, timeout, delay): | |
| 111 """Open the file and lock it. | |
| 112 | |
| 113 Tries to create a .lock file next to the file we're trying to open. | |
| 114 | |
| 115 Args: | |
| 116 timeout: float, How long to try to lock for. | |
| 117 delay: float, How long to wait between retries. | |
| 118 | |
| 119 Raises: | |
| 120 AlreadyLockedException: if the lock is already acquired. | |
| 121 IOError: if the open fails. | |
| 122 CredentialsFileSymbolicLinkError if the file is a symbolic link. | |
| 123 """ | |
| 124 if self._locked: | |
| 125 raise AlreadyLockedException('File %s is already locked' % | |
| 126 self._filename) | |
| 127 self._locked = False | |
| 128 | |
| 129 validate_file(self._filename) | |
| 130 try: | |
| 131 self._fh = open(self._filename, self._mode) | |
| 132 except IOError as e: | |
| 133 # If we can't access with _mode, try _fallback_mode and don't lock. | |
| 134 if e.errno == errno.EACCES: | |
| 135 self._fh = open(self._filename, self._fallback_mode) | |
| 136 return | |
| 137 | |
| 138 lock_filename = self._posix_lockfile(self._filename) | |
| 139 start_time = time.time() | |
| 140 while True: | |
| 141 try: | |
| 142 self._lock_fd = os.open(lock_filename, | |
| 143 os.O_CREAT | os.O_EXCL | os.O_RDWR) | |
| 144 self._locked = True | |
| 145 break | |
| 146 | |
| 147 except OSError as e: | |
| 148 if e.errno != errno.EEXIST: | |
| 149 raise | |
| 150 if (time.time() - start_time) >= timeout: | |
| 151 logger.warn('Could not acquire lock %s in %s seconds', | |
| 152 lock_filename, timeout) | |
| 153 # Close the file and open in fallback_mode. | |
| 154 if self._fh: | |
| 155 self._fh.close() | |
| 156 self._fh = open(self._filename, self._fallback_mode) | |
| 157 return | |
| 158 time.sleep(delay) | |
| 159 | |
| 160 def unlock_and_close(self): | |
| 161 """Unlock a file by removing the .lock file, and close the handle.""" | |
| 162 if self._locked: | |
| 163 lock_filename = self._posix_lockfile(self._filename) | |
| 164 os.close(self._lock_fd) | |
| 165 os.unlink(lock_filename) | |
| 166 self._locked = False | |
| 167 self._lock_fd = None | |
| 168 if self._fh: | |
| 169 self._fh.close() | |
| 170 | |
| 171 def _posix_lockfile(self, filename): | |
| 172 """The name of the lock file to use for posix locking.""" | |
| 173 return '%s.lock' % filename | |
| 174 | |
| 175 | |
| 176 try: | |
| 177 import fcntl | |
| 178 | |
| 179 class _FcntlOpener(_Opener): | |
| 180 """Open, lock, and unlock a file using fcntl.lockf.""" | |
| 181 | |
| 182 def open_and_lock(self, timeout, delay): | |
| 183 """Open the file and lock it. | |
| 184 | |
| 185 Args: | |
| 186 timeout: float, How long to try to lock for. | |
| 187 delay: float, How long to wait between retries | |
| 188 | |
| 189 Raises: | |
| 190 AlreadyLockedException: if the lock is already acquired. | |
| 191 IOError: if the open fails. | |
| 192 CredentialsFileSymbolicLinkError: if the file is a symbolic | |
| 193 link. | |
| 194 """ | |
| 195 if self._locked: | |
| 196 raise AlreadyLockedException('File %s is already locked' % | |
| 197 self._filename) | |
| 198 start_time = time.time() | |
| 199 | |
| 200 validate_file(self._filename) | |
| 201 try: | |
| 202 self._fh = open(self._filename, self._mode) | |
| 203 except IOError as e: | |
| 204 # If we can't access with _mode, try _fallback_mode and | |
| 205 # don't lock. | |
| 206 if e.errno in (errno.EPERM, errno.EACCES): | |
| 207 self._fh = open(self._filename, self._fallback_mode) | |
| 208 return | |
| 209 | |
| 210 # We opened in _mode, try to lock the file. | |
| 211 while True: | |
| 212 try: | |
| 213 fcntl.lockf(self._fh.fileno(), fcntl.LOCK_EX) | |
| 214 self._locked = True | |
| 215 return | |
| 216 except IOError as e: | |
| 217 # If not retrying, then just pass on the error. | |
| 218 if timeout == 0: | |
| 219 raise | |
| 220 if e.errno != errno.EACCES: | |
| 221 raise | |
| 222 # We could not acquire the lock. Try again. | |
| 223 if (time.time() - start_time) >= timeout: | |
| 224 logger.warn('Could not lock %s in %s seconds', | |
| 225 self._filename, timeout) | |
| 226 if self._fh: | |
| 227 self._fh.close() | |
| 228 self._fh = open(self._filename, self._fallback_mode) | |
| 229 return | |
| 230 time.sleep(delay) | |
| 231 | |
| 232 def unlock_and_close(self): | |
| 233 """Close and unlock the file using the fcntl.lockf primitive.""" | |
| 234 if self._locked: | |
| 235 fcntl.lockf(self._fh.fileno(), fcntl.LOCK_UN) | |
| 236 self._locked = False | |
| 237 if self._fh: | |
| 238 self._fh.close() | |
| 239 except ImportError: | |
| 240 _FcntlOpener = None | |
| 241 | |
| 242 | |
| 243 try: | |
| 244 import pywintypes | |
| 245 import win32con | |
| 246 import win32file | |
| 247 | |
| 248 class _Win32Opener(_Opener): | |
| 249 """Open, lock, and unlock a file using windows primitives.""" | |
| 250 | |
| 251 # Error #33: | |
| 252 # 'The process cannot access the file because another process' | |
| 253 FILE_IN_USE_ERROR = 33 | |
| 254 | |
| 255 # Error #158: | |
| 256 # 'The segment is already unlocked.' | |
| 257 FILE_ALREADY_UNLOCKED_ERROR = 158 | |
| 258 | |
| 259 def open_and_lock(self, timeout, delay): | |
| 260 """Open the file and lock it. | |
| 261 | |
| 262 Args: | |
| 263 timeout: float, How long to try to lock for. | |
| 264 delay: float, How long to wait between retries | |
| 265 | |
| 266 Raises: | |
| 267 AlreadyLockedException: if the lock is already acquired. | |
| 268 IOError: if the open fails. | |
| 269 CredentialsFileSymbolicLinkError: if the file is a symbolic | |
| 270 link. | |
| 271 """ | |
| 272 if self._locked: | |
| 273 raise AlreadyLockedException('File %s is already locked' % | |
| 274 self._filename) | |
| 275 start_time = time.time() | |
| 276 | |
| 277 validate_file(self._filename) | |
| 278 try: | |
| 279 self._fh = open(self._filename, self._mode) | |
| 280 except IOError as e: | |
| 281 # If we can't access with _mode, try _fallback_mode | |
| 282 # and don't lock. | |
| 283 if e.errno == errno.EACCES: | |
| 284 self._fh = open(self._filename, self._fallback_mode) | |
| 285 return | |
| 286 | |
| 287 # We opened in _mode, try to lock the file. | |
| 288 while True: | |
| 289 try: | |
| 290 hfile = win32file._get_osfhandle(self._fh.fileno()) | |
| 291 win32file.LockFileEx( | |
| 292 hfile, | |
| 293 (win32con.LOCKFILE_FAIL_IMMEDIATELY | | |
| 294 win32con.LOCKFILE_EXCLUSIVE_LOCK), 0, -0x10000, | |
| 295 pywintypes.OVERLAPPED()) | |
| 296 self._locked = True | |
| 297 return | |
| 298 except pywintypes.error as e: | |
| 299 if timeout == 0: | |
| 300 raise | |
| 301 | |
| 302 # If the error is not that the file is already | |
| 303 # in use, raise. | |
| 304 if e[0] != _Win32Opener.FILE_IN_USE_ERROR: | |
| 305 raise | |
| 306 | |
| 307 # We could not acquire the lock. Try again. | |
| 308 if (time.time() - start_time) >= timeout: | |
| 309 logger.warn('Could not lock %s in %s seconds' % ( | |
| 310 self._filename, timeout)) | |
| 311 if self._fh: | |
| 312 self._fh.close() | |
| 313 self._fh = open(self._filename, self._fallback_mode) | |
| 314 return | |
| 315 time.sleep(delay) | |
| 316 | |
| 317 def unlock_and_close(self): | |
| 318 """Close and unlock the file using the win32 primitive.""" | |
| 319 if self._locked: | |
| 320 try: | |
| 321 hfile = win32file._get_osfhandle(self._fh.fileno()) | |
| 322 win32file.UnlockFileEx(hfile, 0, -0x10000, | |
| 323 pywintypes.OVERLAPPED()) | |
| 324 except pywintypes.error as e: | |
| 325 if e[0] != _Win32Opener.FILE_ALREADY_UNLOCKED_ERROR: | |
| 326 raise | |
| 327 self._locked = False | |
| 328 if self._fh: | |
| 329 self._fh.close() | |
| 330 except ImportError: | |
| 331 _Win32Opener = None | |
| 332 | |
| 333 | |
| 334 class LockedFile(object): | |
| 335 """Represent a file that has exclusive access.""" | |
| 336 | |
| 337 @util.positional(4) | |
| 338 def __init__(self, filename, mode, fallback_mode, use_native_locking=True): | |
| 339 """Construct a LockedFile. | |
| 340 | |
| 341 Args: | |
| 342 filename: string, The path of the file to open. | |
| 343 mode: string, The mode to try to open the file with. | |
| 344 fallback_mode: string, The mode to use if locking fails. | |
| 345 use_native_locking: bool, Whether or not fcntl/win32 locking is | |
| 346 used. | |
| 347 """ | |
| 348 opener = None | |
| 349 if not opener and use_native_locking: | |
| 350 if _Win32Opener: | |
| 351 opener = _Win32Opener(filename, mode, fallback_mode) | |
| 352 if _FcntlOpener: | |
| 353 opener = _FcntlOpener(filename, mode, fallback_mode) | |
| 354 | |
| 355 if not opener: | |
| 356 opener = _PosixOpener(filename, mode, fallback_mode) | |
| 357 | |
| 358 self._opener = opener | |
| 359 | |
| 360 def filename(self): | |
| 361 """Return the filename we were constructed with.""" | |
| 362 return self._opener._filename | |
| 363 | |
| 364 def file_handle(self): | |
| 365 """Return the file_handle to the opened file.""" | |
| 366 return self._opener.file_handle() | |
| 367 | |
| 368 def is_locked(self): | |
| 369 """Return whether we successfully locked the file.""" | |
| 370 return self._opener.is_locked() | |
| 371 | |
| 372 def open_and_lock(self, timeout=0, delay=0.05): | |
| 373 """Open the file, trying to lock it. | |
| 374 | |
| 375 Args: | |
| 376 timeout: float, The number of seconds to try to acquire the lock. | |
| 377 delay: float, The number of seconds to wait between retry attempts. | |
| 378 | |
| 379 Raises: | |
| 380 AlreadyLockedException: if the lock is already acquired. | |
| 381 IOError: if the open fails. | |
| 382 """ | |
| 383 self._opener.open_and_lock(timeout, delay) | |
| 384 | |
| 385 def unlock_and_close(self): | |
| 386 """Unlock and close a file.""" | |
| 387 self._opener.unlock_and_close() | |
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Chromium Code Reviews
Issue 1768993002:
Update oauth2client to v2.0.1 and googleapiclient to v1.5.0.
Base URL: git@github.com:luci/luci-py.git@master