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1 # transaction.py - simple journalling scheme for mercurial
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2 #
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3 # This transaction scheme is intended to gracefully handle program
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4 # errors and interruptions. More serious failures like system crashes
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5 # can be recovered with an fsck-like tool. As the whole repository is
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6 # effectively log-structured, this should amount to simply truncating
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7 # anything that isn't referenced in the changelog.
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8 #
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9 # Copyright 2005, 2006 Matt Mackall <mpm@selenic.com>
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10 #
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11 # This software may be used and distributed according to the terms of the
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12 # GNU General Public License version 2, incorporated herein by reference.
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13
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14 from i18n import _
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15 import os, errno
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16 import error
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17
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18 def active(func):
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19 def _active(self, *args, **kwds):
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20 if self.count == 0:
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21 raise error.Abort(_(
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22 'cannot use transaction when it is already committed/aborted'))
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23 return func(self, *args, **kwds)
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24 return _active
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25
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26 def _playback(journal, report, opener, entries, unlink=True):
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27 for f, o, ignore in entries:
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28 if o or not unlink:
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29 try:
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30 opener(f, 'a').truncate(o)
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31 except:
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32 report(_("failed to truncate %s\n") % f)
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33 raise
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34 else:
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35 try:
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36 fn = opener(f).name
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37 os.unlink(fn)
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38 except IOError, inst:
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39 if inst.errno != errno.ENOENT:
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40 raise
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41 os.unlink(journal)
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42
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43 class transaction(object):
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44 def __init__(self, report, opener, journal, after=None, createmode=None):
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45 self.journal = None
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46
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47 self.count = 1
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48 self.report = report
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49 self.opener = opener
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50 self.after = after
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51 self.entries = []
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52 self.map = {}
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53 self.journal = journal
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54 self._queue = []
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55
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56 self.file = open(self.journal, "w")
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57 if createmode is not None:
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58 os.chmod(self.journal, createmode & 0666)
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59
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60 def __del__(self):
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61 if self.journal:
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62 if self.entries: self._abort()
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63 self.file.close()
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64
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65 @active
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66 def startgroup(self):
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67 self._queue.append([])
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68
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69 @active
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70 def endgroup(self):
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71 q = self._queue.pop()
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72 d = ''.join(['%s\0%d\n' % (x[0], x[1]) for x in q])
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73 self.entries.extend(q)
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74 self.file.write(d)
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75 self.file.flush()
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76
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77 @active
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78 def add(self, file, offset, data=None):
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79 if file in self.map: return
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80
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81 if self._queue:
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82 self._queue[-1].append((file, offset, data))
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83 return
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84
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85 self.entries.append((file, offset, data))
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86 self.map[file] = len(self.entries) - 1
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87 # add enough data to the journal to do the truncate
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88 self.file.write("%s\0%d\n" % (file, offset))
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89 self.file.flush()
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90
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91 @active
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92 def find(self, file):
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93 if file in self.map:
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94 return self.entries[self.map[file]]
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95 return None
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96
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97 @active
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98 def replace(self, file, offset, data=None):
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99 '''
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100 replace can only replace already committed entries
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101 that are not pending in the queue
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102 '''
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103
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104 if file not in self.map:
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105 raise KeyError(file)
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106 index = self.map[file]
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107 self.entries[index] = (file, offset, data)
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108 self.file.write("%s\0%d\n" % (file, offset))
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109 self.file.flush()
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110
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111 @active
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112 def nest(self):
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113 self.count += 1
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114 return self
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115
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116 def running(self):
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117 return self.count > 0
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118
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119 @active
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120 def close(self):
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121 self.count -= 1
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122 if self.count != 0:
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123 return
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124 self.file.close()
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125 self.entries = []
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126 if self.after:
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127 self.after()
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128 else:
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129 os.unlink(self.journal)
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130 self.journal = None
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131
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132 @active
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133 def abort(self):
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134 self._abort()
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135
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136 def _abort(self):
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137 self.count = 0
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138 self.file.close()
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139
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140 if not self.entries: return
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141
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142 self.report(_("transaction abort!\n"))
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143
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144 try:
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145 try:
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146 _playback(self.journal, self.report, self.opener, self.entries, False)
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147 self.report(_("rollback completed\n"))
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148 except:
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149 self.report(_("rollback failed - please run hg recover\n"))
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150 finally:
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151 self.journal = None
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152
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153
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154 def rollback(opener, file, report):
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155 entries = []
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156
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157 for l in open(file).readlines():
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158 f, o = l.split('\0')
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159 entries.append((f, int(o), None))
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160
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161 _playback(file, report, opener, entries)
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