4 # Copyright (C) 2006, 2007 Google Inc.
6 # This program is free software; you can redistribute it and/or modify
7 # it under the terms of the GNU General Public License as published by
8 # the Free Software Foundation; either version 2 of the License, or
9 # (at your option) any later version.
11 # This program is distributed in the hope that it will be useful, but
12 # WITHOUT ANY WARRANTY; without even the implied warranty of
13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 # General Public License for more details.
16 # You should have received a copy of the GNU General Public License
17 # along with this program; if not, write to the Free Software
18 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
22 """Module implementing the job queue handling."""
27 from ganeti import constants
28 from ganeti import errors
29 from ganeti import utils
32 def _ReadNumericFile(file_name):
33 """Reads a file containing a number.
36 @return: None if file is not found, otherwise number
40 fd = open(file_name, "r")
42 if err.errno in (errno.ENOENT, ):
47 return int(fd.read(128))
53 """Read the serial file.
55 The queue should be locked while this function is called.
58 return _ReadNumericFile(constants.JOB_QUEUE_SERIAL_FILE)
62 """Read the queue version.
64 The queue should be locked while this function is called.
67 return _ReadNumericFile(constants.JOB_QUEUE_VERSION_FILE)
70 def InitAndVerifyQueue(must_lock):
71 """Open and lock job queue.
73 If necessary, the queue is automatically initialized.
76 @param must_lock: Whether an exclusive lock must be held.
77 @rtype: utils.FileLock
78 @return: Lock object for the queue. This can be used to change the
82 # Make sure our directories exists
83 for path in (constants.QUEUE_DIR, constants.JOB_QUEUE_ARCHIVE_DIR):
87 if err.errno not in (errno.EEXIST, ):
91 queue_lock = utils.FileLock(constants.JOB_QUEUE_LOCK_FILE)
93 # The queue needs to be locked in exclusive mode to write to the serial and
96 queue_lock.Exclusive(blocking=True)
100 queue_lock.Exclusive(blocking=False)
102 except errors.LockError:
103 # Ignore errors and assume the process keeping the lock checked
109 version = ReadVersion()
111 # Write new version file
112 utils.WriteFile(constants.JOB_QUEUE_VERSION_FILE,
113 data="%s\n" % constants.JOB_QUEUE_VERSION)
116 version = ReadVersion()
118 if version != constants.JOB_QUEUE_VERSION:
119 raise errors.JobQueueError("Found job queue version %s, expected %s",
120 version, constants.JOB_QUEUE_VERSION)
122 serial = ReadSerial()
124 # Write new serial file
125 utils.WriteFile(constants.JOB_QUEUE_SERIAL_FILE,
129 serial = ReadSerial()
132 # There must be a serious problem
133 raise errors.JobQueueError("Can't read/parse the job queue serial file")
136 # There's no need for more error handling. Closing the lock file below in
137 # case of an error will unlock it anyway.