root / lib / jstore.py @ 4008c8ed
History | View | Annotate | Download (3.6 kB)
1 |
#
|
---|---|
2 |
#
|
3 |
|
4 |
# Copyright (C) 2006, 2007 Google Inc.
|
5 |
#
|
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.
|
10 |
#
|
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.
|
15 |
#
|
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
|
19 |
# 02110-1301, USA.
|
20 |
|
21 |
|
22 |
"""Module implementing the job queue handling."""
|
23 |
|
24 |
import errno |
25 |
|
26 |
from ganeti import constants |
27 |
from ganeti import errors |
28 |
from ganeti import utils |
29 |
|
30 |
|
31 |
def _ReadNumericFile(file_name): |
32 |
"""Reads a file containing a number.
|
33 |
|
34 |
@rtype: None or int
|
35 |
@return: None if file is not found, otherwise number
|
36 |
|
37 |
"""
|
38 |
try:
|
39 |
return int(utils.ReadFile(file_name)) |
40 |
except EnvironmentError, err: |
41 |
if err.errno in (errno.ENOENT, ): |
42 |
return None |
43 |
raise
|
44 |
|
45 |
|
46 |
def ReadSerial(): |
47 |
"""Read the serial file.
|
48 |
|
49 |
The queue should be locked while this function is called.
|
50 |
|
51 |
"""
|
52 |
return _ReadNumericFile(constants.JOB_QUEUE_SERIAL_FILE)
|
53 |
|
54 |
|
55 |
def ReadVersion(): |
56 |
"""Read the queue version.
|
57 |
|
58 |
The queue should be locked while this function is called.
|
59 |
|
60 |
"""
|
61 |
return _ReadNumericFile(constants.JOB_QUEUE_VERSION_FILE)
|
62 |
|
63 |
|
64 |
def InitAndVerifyQueue(must_lock): |
65 |
"""Open and lock job queue.
|
66 |
|
67 |
If necessary, the queue is automatically initialized.
|
68 |
|
69 |
@type must_lock: bool
|
70 |
@param must_lock: Whether an exclusive lock must be held.
|
71 |
@rtype: utils.FileLock
|
72 |
@return: Lock object for the queue. This can be used to change the
|
73 |
locking mode.
|
74 |
|
75 |
"""
|
76 |
dirs = [(d, constants.JOB_QUEUE_DIRS_MODE) for d in constants.JOB_QUEUE_DIRS] |
77 |
utils.EnsureDirs(dirs) |
78 |
|
79 |
# Lock queue
|
80 |
queue_lock = utils.FileLock.Open(constants.JOB_QUEUE_LOCK_FILE) |
81 |
try:
|
82 |
# The queue needs to be locked in exclusive mode to write to the serial and
|
83 |
# version files.
|
84 |
if must_lock:
|
85 |
queue_lock.Exclusive(blocking=True)
|
86 |
holding_lock = True
|
87 |
else:
|
88 |
try:
|
89 |
queue_lock.Exclusive(blocking=False)
|
90 |
holding_lock = True
|
91 |
except errors.LockError:
|
92 |
# Ignore errors and assume the process keeping the lock checked
|
93 |
# everything.
|
94 |
holding_lock = False
|
95 |
|
96 |
if holding_lock:
|
97 |
# Verify version
|
98 |
version = ReadVersion() |
99 |
if version is None: |
100 |
# Write new version file
|
101 |
utils.WriteFile(constants.JOB_QUEUE_VERSION_FILE, |
102 |
data="%s\n" % constants.JOB_QUEUE_VERSION)
|
103 |
|
104 |
# Read again
|
105 |
version = ReadVersion() |
106 |
|
107 |
if version != constants.JOB_QUEUE_VERSION:
|
108 |
raise errors.JobQueueError("Found job queue version %s, expected %s", |
109 |
version, constants.JOB_QUEUE_VERSION) |
110 |
|
111 |
serial = ReadSerial() |
112 |
if serial is None: |
113 |
# Write new serial file
|
114 |
utils.WriteFile(constants.JOB_QUEUE_SERIAL_FILE, |
115 |
data="%s\n" % 0) |
116 |
|
117 |
# Read again
|
118 |
serial = ReadSerial() |
119 |
|
120 |
if serial is None: |
121 |
# There must be a serious problem
|
122 |
raise errors.JobQueueError("Can't read/parse the job queue" |
123 |
" serial file")
|
124 |
|
125 |
if not must_lock: |
126 |
# There's no need for more error handling. Closing the lock
|
127 |
# file below in case of an error will unlock it anyway.
|
128 |
queue_lock.Unlock() |
129 |
|
130 |
except:
|
131 |
queue_lock.Close() |
132 |
raise
|
133 |
|
134 |
return queue_lock
|