Mercurial > repos > shellac > guppy_basecaller

comparison env/lib/python3.7/site-packages/lockfile/pidlockfile.py @ 0:26e78fe6e8c4 draft

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
"planemo upload commit c699937486c35866861690329de38ec1a5d9f783"
author shellac
date Sat, 02 May 2020 07:14:21 -0400
parents
children
comparison
equal deleted inserted replaced
-1:000000000000 0:26e78fe6e8c4
1 # -*- coding: utf-8 -*-
2
3 # pidlockfile.py
4 #
5 # Copyright © 2008–2009 Ben Finney <ben+python@benfinney.id.au>
6 #
7 # This is free software: you may copy, modify, and/or distribute this work
8 # under the terms of the Python Software Foundation License, version 2 or
9 # later as published by the Python Software Foundation.
10 # No warranty expressed or implied. See the file LICENSE.PSF-2 for details.
11
12 """ Lockfile behaviour implemented via Unix PID files.
13 """
14
15 from __future__ import absolute_import
16
17 import errno
18 import os
19 import time
20
21 from . import (LockBase, AlreadyLocked, LockFailed, NotLocked, NotMyLock,
22 LockTimeout)
23
24
25 class PIDLockFile(LockBase):
26 """ Lockfile implemented as a Unix PID file.
27
28 The lock file is a normal file named by the attribute `path`.
29 A lock's PID file contains a single line of text, containing
30 the process ID (PID) of the process that acquired the lock.
31
32 >>> lock = PIDLockFile('somefile')
33 >>> lock = PIDLockFile('somefile')
34 """
35
36 def __init__(self, path, threaded=False, timeout=None):
37 # pid lockfiles don't support threaded operation, so always force
38 # False as the threaded arg.
39 LockBase.__init__(self, path, False, timeout)
40 self.unique_name = self.path
41
42 def read_pid(self):
43 """ Get the PID from the lock file.
44 """
45 return read_pid_from_pidfile(self.path)
46
47 def is_locked(self):
48 """ Test if the lock is currently held.
49
50 The lock is held if the PID file for this lock exists.
51
52 """
53 return os.path.exists(self.path)
54
55 def i_am_locking(self):
56 """ Test if the lock is held by the current process.
57
58 Returns ``True`` if the current process ID matches the
59 number stored in the PID file.
60 """
61 return self.is_locked() and os.getpid() == self.read_pid()
62
63 def acquire(self, timeout=None):
64 """ Acquire the lock.
65
66 Creates the PID file for this lock, or raises an error if
67 the lock could not be acquired.
68 """
69
70 timeout = timeout if timeout is not None else self.timeout
71 end_time = time.time()
72 if timeout is not None and timeout > 0:
73 end_time += timeout
74
75 while True:
76 try:
77 write_pid_to_pidfile(self.path)
78 except OSError as exc:
79 if exc.errno == errno.EEXIST:
80 # The lock creation failed. Maybe sleep a bit.
81 if time.time() > end_time:
82 if timeout is not None and timeout > 0:
83 raise LockTimeout("Timeout waiting to acquire"
84 " lock for %s" %
85 self.path)
86 else:
87 raise AlreadyLocked("%s is already locked" %
88 self.path)
89 time.sleep(timeout is not None and timeout / 10 or 0.1)
90 else:
91 raise LockFailed("failed to create %s" % self.path)
92 else:
93 return
94
95 def release(self):
96 """ Release the lock.
97
98 Removes the PID file to release the lock, or raises an
99 error if the current process does not hold the lock.
100
101 """
102 if not self.is_locked():
103 raise NotLocked("%s is not locked" % self.path)
104 if not self.i_am_locking():
105 raise NotMyLock("%s is locked, but not by me" % self.path)
106 remove_existing_pidfile(self.path)
107
108 def break_lock(self):
109 """ Break an existing lock.
110
111 Removes the PID file if it already exists, otherwise does
112 nothing.
113
114 """
115 remove_existing_pidfile(self.path)
116
117
118 def read_pid_from_pidfile(pidfile_path):
119 """ Read the PID recorded in the named PID file.
120
121 Read and return the numeric PID recorded as text in the named
122 PID file. If the PID file cannot be read, or if the content is
123 not a valid PID, return ``None``.
124
125 """
126 pid = None
127 try:
128 pidfile = open(pidfile_path, 'r')
129 except IOError:
130 pass
131 else:
132 # According to the FHS 2.3 section on PID files in /var/run:
133 #
134 # The file must consist of the process identifier in
135 # ASCII-encoded decimal, followed by a newline character.
136 #
137 # Programs that read PID files should be somewhat flexible
138 # in what they accept; i.e., they should ignore extra
139 # whitespace, leading zeroes, absence of the trailing
140 # newline, or additional lines in the PID file.
141
142 line = pidfile.readline().strip()
143 try:
144 pid = int(line)
145 except ValueError:
146 pass
147 pidfile.close()
148
149 return pid
150
151
152 def write_pid_to_pidfile(pidfile_path):
153 """ Write the PID in the named PID file.
154
155 Get the numeric process ID (“PID”) of the current process
156 and write it to the named file as a line of text.
157
158 """
159 open_flags = (os.O_CREAT | os.O_EXCL | os.O_WRONLY)
160 open_mode = 0o644
161 pidfile_fd = os.open(pidfile_path, open_flags, open_mode)
162 pidfile = os.fdopen(pidfile_fd, 'w')
163
164 # According to the FHS 2.3 section on PID files in /var/run:
165 #
166 # The file must consist of the process identifier in
167 # ASCII-encoded decimal, followed by a newline character. For
168 # example, if crond was process number 25, /var/run/crond.pid
169 # would contain three characters: two, five, and newline.
170
171 pid = os.getpid()
172 pidfile.write("%s\n" % pid)
173 pidfile.close()
174
175
176 def remove_existing_pidfile(pidfile_path):
177 """ Remove the named PID file if it exists.
178
179 Removing a PID file that doesn't already exist puts us in the
180 desired state, so we ignore the condition if the file does not
181 exist.
182
183 """
184 try:
185 os.remove(pidfile_path)
186 except OSError as exc:
187 if exc.errno == errno.ENOENT:
188 pass
189 else:
190 raise