157 lines
5.4 KiB
Python
157 lines
5.4 KiB
Python
|
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 if timeout is not None else 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()
|