Mercurial > repos > guerler > springsuite

annotate planemo/lib/python3.7/site-packages/lockfile/pidlockfile.py @ 1:56ad4e20f292 draft

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"planemo upload commit 6eee67778febed82ddd413c3ca40b3183a3898f1"
author guerler
date Fri, 31 Jul 2020 00:32:28 -0400
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1
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1 # -*- coding: utf-8 -*-
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2
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3 # pidlockfile.py
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4 #
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5 # Copyright © 2008–2009 Ben Finney <ben+python@benfinney.id.au>
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6 #
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7 # This is free software: you may copy, modify, and/or distribute this work
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8 # under the terms of the Python Software Foundation License, version 2 or
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9 # later as published by the Python Software Foundation.
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10 # No warranty expressed or implied. See the file LICENSE.PSF-2 for details.
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11
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12 """ Lockfile behaviour implemented via Unix PID files.
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13 """
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14
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15 from __future__ import absolute_import
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16
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17 import errno
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18 import os
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19 import time
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20
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21 from . import (LockBase, AlreadyLocked, LockFailed, NotLocked, NotMyLock,
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22 LockTimeout)
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23
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24
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25 class PIDLockFile(LockBase):
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26 """ Lockfile implemented as a Unix PID file.
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27
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28 The lock file is a normal file named by the attribute `path`.
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29 A lock's PID file contains a single line of text, containing
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30 the process ID (PID) of the process that acquired the lock.
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31
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32 >>> lock = PIDLockFile('somefile')
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33 >>> lock = PIDLockFile('somefile')
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34 """
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35
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36 def __init__(self, path, threaded=False, timeout=None):
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37 # pid lockfiles don't support threaded operation, so always force
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38 # False as the threaded arg.
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39 LockBase.__init__(self, path, False, timeout)
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40 self.unique_name = self.path
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41
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42 def read_pid(self):
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43 """ Get the PID from the lock file.
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44 """
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45 return read_pid_from_pidfile(self.path)
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46
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47 def is_locked(self):
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48 """ Test if the lock is currently held.
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49
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50 The lock is held if the PID file for this lock exists.
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51
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52 """
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53 return os.path.exists(self.path)
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54
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55 def i_am_locking(self):
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56 """ Test if the lock is held by the current process.
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57
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58 Returns ``True`` if the current process ID matches the
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59 number stored in the PID file.
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60 """
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61 return self.is_locked() and os.getpid() == self.read_pid()
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62
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63 def acquire(self, timeout=None):
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64 """ Acquire the lock.
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65
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66 Creates the PID file for this lock, or raises an error if
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67 the lock could not be acquired.
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68 """
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69
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70 timeout = timeout if timeout is not None else self.timeout
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71 end_time = time.time()
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72 if timeout is not None and timeout > 0:
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73 end_time += timeout
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74
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75 while True:
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76 try:
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77 write_pid_to_pidfile(self.path)
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78 except OSError as exc:
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79 if exc.errno == errno.EEXIST:
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80 # The lock creation failed. Maybe sleep a bit.
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81 if time.time() > end_time:
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82 if timeout is not None and timeout > 0:
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83 raise LockTimeout("Timeout waiting to acquire"
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84 " lock for %s" %
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85 self.path)
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86 else:
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87 raise AlreadyLocked("%s is already locked" %
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88 self.path)
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89 time.sleep(timeout is not None and timeout / 10 or 0.1)
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90 else:
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91 raise LockFailed("failed to create %s" % self.path)
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92 else:
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93 return
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94
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95 def release(self):
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96 """ Release the lock.
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97
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98 Removes the PID file to release the lock, or raises an
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99 error if the current process does not hold the lock.
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100
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101 """
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102 if not self.is_locked():
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103 raise NotLocked("%s is not locked" % self.path)
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104 if not self.i_am_locking():
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105 raise NotMyLock("%s is locked, but not by me" % self.path)
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106 remove_existing_pidfile(self.path)
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107
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108 def break_lock(self):
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109 """ Break an existing lock.
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110
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111 Removes the PID file if it already exists, otherwise does
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112 nothing.
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113
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114 """
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115 remove_existing_pidfile(self.path)
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116
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117
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118 def read_pid_from_pidfile(pidfile_path):
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119 """ Read the PID recorded in the named PID file.
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120
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121 Read and return the numeric PID recorded as text in the named
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122 PID file. If the PID file cannot be read, or if the content is
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123 not a valid PID, return ``None``.
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124
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125 """
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126 pid = None
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127 try:
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128 pidfile = open(pidfile_path, 'r')
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129 except IOError:
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130 pass
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131 else:
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132 # According to the FHS 2.3 section on PID files in /var/run:
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133 #
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134 # The file must consist of the process identifier in
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135 # ASCII-encoded decimal, followed by a newline character.
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136 #
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137 # Programs that read PID files should be somewhat flexible
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138 # in what they accept; i.e., they should ignore extra
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139 # whitespace, leading zeroes, absence of the trailing
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140 # newline, or additional lines in the PID file.
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141
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142 line = pidfile.readline().strip()
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143 try:
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144 pid = int(line)
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145 except ValueError:
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146 pass
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147 pidfile.close()
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148
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149 return pid
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150
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151
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152 def write_pid_to_pidfile(pidfile_path):
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153 """ Write the PID in the named PID file.
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154
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155 Get the numeric process ID (“PID”) of the current process
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156 and write it to the named file as a line of text.
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157
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158 """
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159 open_flags = (os.O_CREAT | os.O_EXCL | os.O_WRONLY)
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160 open_mode = 0o644
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161 pidfile_fd = os.open(pidfile_path, open_flags, open_mode)
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162 pidfile = os.fdopen(pidfile_fd, 'w')
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163
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164 # According to the FHS 2.3 section on PID files in /var/run:
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165 #
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166 # The file must consist of the process identifier in
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167 # ASCII-encoded decimal, followed by a newline character. For
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168 # example, if crond was process number 25, /var/run/crond.pid
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169 # would contain three characters: two, five, and newline.
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170
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171 pid = os.getpid()
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172 pidfile.write("%s\n" % pid)
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173 pidfile.close()
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174
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175
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176 def remove_existing_pidfile(pidfile_path):
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177 """ Remove the named PID file if it exists.
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178
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179 Removing a PID file that doesn't already exist puts us in the
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180 desired state, so we ignore the condition if the file does not
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181 exist.
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182
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183 """
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184 try:
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185 os.remove(pidfile_path)
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186 except OSError as exc:
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187 if exc.errno == errno.ENOENT:
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188 pass
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189 else:
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190 raise