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."""
26 from ganeti import constants
27 from ganeti import errors
28 from ganeti import utils
31 def _ReadNumericFile(file_name):
32 """Reads a file containing a number.
35 @return: None if file is not found, otherwise number
39 fd = open(file_name, "r")
41 if err.errno in (errno.ENOENT, ):
46 return int(fd.read(128))
52 """Read the serial file.
54 The queue should be locked while this function is called.
57 return _ReadNumericFile(constants.JOB_QUEUE_SERIAL_FILE)
61 """Read the queue version.
63 The queue should be locked while this function is called.
66 return _ReadNumericFile(constants.JOB_QUEUE_VERSION_FILE)
69 def InitAndVerifyQueue(must_lock):
70 """Open and lock job queue.
72 If necessary, the queue is automatically initialized.
75 @param must_lock: Whether an exclusive lock must be held.
76 @rtype: utils.FileLock
77 @return: Lock object for the queue. This can be used to change the
81 dirs = [(d, constants.JOB_QUEUE_DIRS_MODE) for d in constants.JOB_QUEUE_DIRS]
82 utils.EnsureDirs(dirs)
85 queue_lock = utils.FileLock.Open(constants.JOB_QUEUE_LOCK_FILE)
87 # The queue needs to be locked in exclusive mode to write to the serial and
90 queue_lock.Exclusive(blocking=True)
94 queue_lock.Exclusive(blocking=False)
96 except errors.LockError:
97 # Ignore errors and assume the process keeping the lock checked
103 version = ReadVersion()
105 # Write new version file
106 utils.WriteFile(constants.JOB_QUEUE_VERSION_FILE,
107 data="%s\n" % constants.JOB_QUEUE_VERSION)
110 version = ReadVersion()
112 if version != constants.JOB_QUEUE_VERSION:
113 raise errors.JobQueueError("Found job queue version %s, expected %s",
114 version, constants.JOB_QUEUE_VERSION)
116 serial = ReadSerial()
118 # Write new serial file
119 utils.WriteFile(constants.JOB_QUEUE_SERIAL_FILE,
123 serial = ReadSerial()
126 # There must be a serious problem
127 raise errors.JobQueueError("Can't read/parse the job queue"
131 # There's no need for more error handling. Closing the lock
132 # file below in case of an error will unlock it anyway.