1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
|
from __future__ import absolute_import, division
import time
import os
try:
unicode
except NameError:
unicode = str
from . import LockBase, NotLocked, NotMyLock, LockTimeout, AlreadyLocked
class SQLiteLockFile(LockBase):
"Demonstrate SQL-based locking."
testdb = None
def __init__(self, path, threaded=True, timeout=None):
"""
>>> lock = SQLiteLockFile('somefile')
>>> lock = SQLiteLockFile('somefile', threaded=False)
"""
LockBase.__init__(self, path, threaded, timeout)
self.lock_file = unicode(self.lock_file)
self.unique_name = unicode(self.unique_name)
if SQLiteLockFile.testdb is None:
import tempfile
_fd, testdb = tempfile.mkstemp()
os.close(_fd)
os.unlink(testdb)
del _fd, tempfile
SQLiteLockFile.testdb = testdb
import sqlite3
self.connection = sqlite3.connect(SQLiteLockFile.testdb)
c = self.connection.cursor()
try:
c.execute("create table locks"
"("
" lock_file varchar(32),"
" unique_name varchar(32)"
")")
except sqlite3.OperationalError:
pass
else:
self.connection.commit()
import atexit
atexit.register(os.unlink, SQLiteLockFile.testdb)
def acquire(self, timeout=None):
timeout = timeout is not None and timeout or self.timeout
end_time = time.time()
if timeout is not None and timeout > 0:
end_time += timeout
if timeout is None:
wait = 0.1
elif timeout <= 0:
wait = 0
else:
wait = timeout / 10
cursor = self.connection.cursor()
while True:
if not self.is_locked():
# Not locked. Try to lock it.
cursor.execute("insert into locks"
" (lock_file, unique_name)"
" values"
" (?, ?)",
(self.lock_file, self.unique_name))
self.connection.commit()
# Check to see if we are the only lock holder.
cursor.execute("select * from locks"
" where unique_name = ?",
(self.unique_name,))
rows = cursor.fetchall()
if len(rows) > 1:
# Nope. Someone else got there. Remove our lock.
cursor.execute("delete from locks"
" where unique_name = ?",
(self.unique_name,))
self.connection.commit()
else:
# Yup. We're done, so go home.
return
else:
# Check to see if we are the only lock holder.
cursor.execute("select * from locks"
" where unique_name = ?",
(self.unique_name,))
rows = cursor.fetchall()
if len(rows) == 1:
# We're the locker, so go home.
return
# Maybe we should wait a bit longer.
if timeout is not None and time.time() > end_time:
if timeout > 0:
# No more waiting.
raise LockTimeout("Timeout waiting to acquire"
" lock for %s" %
self.path)
else:
# Someone else has the lock and we are impatient..
raise AlreadyLocked("%s is already locked" % self.path)
# Well, okay. We'll give it a bit longer.
time.sleep(wait)
def release(self):
if not self.is_locked():
raise NotLocked("%s is not locked" % self.path)
if not self.i_am_locking():
raise NotMyLock("%s is locked, but not by me (by %s)" %
(self.unique_name, self._who_is_locking()))
cursor = self.connection.cursor()
cursor.execute("delete from locks"
" where unique_name = ?",
(self.unique_name,))
self.connection.commit()
def _who_is_locking(self):
cursor = self.connection.cursor()
cursor.execute("select unique_name from locks"
" where lock_file = ?",
(self.lock_file,))
return cursor.fetchone()[0]
def is_locked(self):
cursor = self.connection.cursor()
cursor.execute("select * from locks"
" where lock_file = ?",
(self.lock_file,))
rows = cursor.fetchall()
return not not rows
def i_am_locking(self):
cursor = self.connection.cursor()
cursor.execute("select * from locks"
" where lock_file = ?"
" and unique_name = ?",
(self.lock_file, self.unique_name))
return not not cursor.fetchall()
def break_lock(self):
cursor = self.connection.cursor()
cursor.execute("delete from locks"
" where lock_file = ?",
(self.lock_file,))
self.connection.commit()
|