root / lib / jstore.py @ ee513a66
History | View | Annotate | Download (3.8 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 os |
25 |
import logging |
26 |
import errno |
27 |
import re |
28 |
|
29 |
from ganeti import constants |
30 |
from ganeti import errors |
31 |
from ganeti import utils |
32 |
|
33 |
|
34 |
def _ReadNumericFile(file_name): |
35 |
"""Reads a file containing a number.
|
36 |
|
37 |
@rtype: None or int
|
38 |
@return: None if file is not found, otherwise number
|
39 |
|
40 |
"""
|
41 |
try:
|
42 |
fd = open(file_name, "r") |
43 |
except IOError, err: |
44 |
if err.errno in (errno.ENOENT, ): |
45 |
return None |
46 |
raise
|
47 |
|
48 |
try:
|
49 |
return int(fd.read(128)) |
50 |
finally:
|
51 |
fd.close() |
52 |
|
53 |
|
54 |
def ReadSerial(): |
55 |
"""Read the serial file.
|
56 |
|
57 |
The queue should be locked while this function is called.
|
58 |
|
59 |
"""
|
60 |
return _ReadNumericFile(constants.JOB_QUEUE_SERIAL_FILE)
|
61 |
|
62 |
|
63 |
def ReadVersion(): |
64 |
"""Read the queue version.
|
65 |
|
66 |
The queue should be locked while this function is called.
|
67 |
|
68 |
"""
|
69 |
return _ReadNumericFile(constants.JOB_QUEUE_VERSION_FILE)
|
70 |
|
71 |
|
72 |
def InitAndVerifyQueue(must_lock): |
73 |
"""Open and lock job queue.
|
74 |
|
75 |
If necessary, the queue is automatically initialized.
|
76 |
|
77 |
@type must_lock: bool
|
78 |
@param must_lock: Whether an exclusive lock must be held.
|
79 |
@rtype: utils.FileLock
|
80 |
@return: Lock object for the queue. This can be used to change the
|
81 |
locking mode.
|
82 |
|
83 |
"""
|
84 |
# Make sure our directories exists
|
85 |
for path in (constants.QUEUE_DIR, constants.JOB_QUEUE_ARCHIVE_DIR): |
86 |
try:
|
87 |
os.mkdir(path, 0700)
|
88 |
except OSError, err: |
89 |
if err.errno not in (errno.EEXIST, ): |
90 |
raise
|
91 |
|
92 |
# Lock queue
|
93 |
queue_lock = utils.FileLock(constants.JOB_QUEUE_LOCK_FILE) |
94 |
try:
|
95 |
# The queue needs to be locked in exclusive mode to write to the serial and
|
96 |
# version files.
|
97 |
if must_lock:
|
98 |
queue_lock.Exclusive(blocking=True)
|
99 |
holding_lock = True
|
100 |
else:
|
101 |
try:
|
102 |
queue_lock.Exclusive(blocking=False)
|
103 |
holding_lock = True
|
104 |
except errors.LockError:
|
105 |
# Ignore errors and assume the process keeping the lock checked
|
106 |
# everything.
|
107 |
holding_lock = False
|
108 |
|
109 |
if holding_lock:
|
110 |
# Verify version
|
111 |
version = ReadVersion() |
112 |
if version is None: |
113 |
# Write new version file
|
114 |
utils.WriteFile(constants.JOB_QUEUE_VERSION_FILE, |
115 |
data="%s\n" % constants.JOB_QUEUE_VERSION)
|
116 |
|
117 |
# Read again
|
118 |
version = ReadVersion() |
119 |
|
120 |
if version != constants.JOB_QUEUE_VERSION:
|
121 |
raise errors.JobQueueError("Found job queue version %s, expected %s", |
122 |
version, constants.JOB_QUEUE_VERSION) |
123 |
|
124 |
serial = ReadSerial() |
125 |
if serial is None: |
126 |
# Write new serial file
|
127 |
utils.WriteFile(constants.JOB_QUEUE_SERIAL_FILE, |
128 |
data="%s\n" % 0) |
129 |
|
130 |
# Read again
|
131 |
serial = ReadSerial() |
132 |
|
133 |
if serial is None: |
134 |
# There must be a serious problem
|
135 |
raise errors.JobQueueError("Can't read/parse the job queue serial file") |
136 |
|
137 |
if not must_lock: |
138 |
# There's no need for more error handling. Closing the lock file below in
|
139 |
# case of an error will unlock it anyway.
|
140 |
queue_lock.Unlock() |
141 |
|
142 |
except:
|
143 |
queue_lock.Close() |
144 |
raise
|
145 |
|
146 |
return queue_lock
|