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1 | # transaction.py - simple journalling scheme for mercurial |
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1 | # transaction.py - simple journalling scheme for mercurial | |
2 | # |
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2 | # | |
3 | # This transaction scheme is intended to gracefully handle program |
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3 | # This transaction scheme is intended to gracefully handle program | |
4 | # errors and interruptions. More serious failures like system crashes |
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4 | # errors and interruptions. More serious failures like system crashes | |
5 | # can be recovered with an fsck-like tool. As the whole repository is |
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5 | # can be recovered with an fsck-like tool. As the whole repository is | |
6 | # effectively log-structured, this should amount to simply truncating |
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6 | # effectively log-structured, this should amount to simply truncating | |
7 | # anything that isn't referenced in the changelog. |
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7 | # anything that isn't referenced in the changelog. | |
8 | # |
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8 | # | |
9 | # Copyright 2005 Matt Mackall <mpm@selenic.com> |
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9 | # Copyright 2005 Matt Mackall <mpm@selenic.com> | |
10 | # |
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10 | # | |
11 | # This software may be used and distributed according to the terms |
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11 | # This software may be used and distributed according to the terms | |
12 | # of the GNU General Public License, incorporated herein by reference. |
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12 | # of the GNU General Public License, incorporated herein by reference. | |
13 |
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13 | |||
14 | import os |
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14 | import os | |
15 |
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15 | |||
16 | class transaction: |
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16 | class transaction: | |
17 | def __init__(self, opener, journal): |
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17 | def __init__(self, opener, journal): | |
18 | self.opener = opener |
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18 | self.opener = opener | |
19 | self.entries = [] |
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19 | self.entries = [] | |
20 | self.map = {} |
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20 | self.map = {} | |
21 | self.journal = journal |
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21 | self.journal = journal | |
22 |
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22 | |||
23 | # abort here if the journal already exists |
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23 | # abort here if the journal already exists | |
24 | if os.path.exists(self.journal): |
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24 | if os.path.exists(self.journal): | |
25 |
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25 | print "journal already exists, recovering" | |
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26 | self.recover() | |||
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27 | ||||
26 | self.file = open(self.journal, "w") |
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28 | self.file = open(self.journal, "w") | |
27 |
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29 | |||
28 | def __del__(self): |
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30 | def __del__(self): | |
29 | if self.entries: self.abort() |
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31 | if self.entries: self.abort() | |
30 | try: os.unlink(self.journal) |
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32 | try: os.unlink(self.journal) | |
31 | except: pass |
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33 | except: pass | |
32 |
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34 | |||
33 | def add(self, file, offset): |
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35 | def add(self, file, offset): | |
34 | if file in self.map: return |
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36 | if file in self.map: return | |
35 | self.entries.append((file, offset)) |
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37 | self.entries.append((file, offset)) | |
36 | self.map[file] = 1 |
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38 | self.map[file] = 1 | |
37 | # add enough data to the journal to do the truncate |
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39 | # add enough data to the journal to do the truncate | |
38 | self.file.write("%s\0%d\n" % (file, offset)) |
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40 | self.file.write("%s\0%d\n" % (file, offset)) | |
39 | self.file.flush() |
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41 | self.file.flush() | |
40 |
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42 | |||
41 | def close(self): |
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43 | def close(self): | |
42 | self.file.close() |
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44 | self.file.close() | |
43 | self.entries = [] |
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45 | self.entries = [] | |
44 | os.unlink(self.journal) |
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46 | os.unlink(self.journal) | |
45 |
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47 | |||
46 | def abort(self): |
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48 | def abort(self): | |
47 | if not self.entries: return |
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49 | if not self.entries: return | |
48 |
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50 | |||
49 | print "transaction abort!" |
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51 | print "transaction abort!" | |
50 |
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52 | |||
51 | for f, o in self.entries: |
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53 | for f, o in self.entries: | |
52 | self.opener(f, "a").truncate(o) |
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54 | self.opener(f, "a").truncate(o) | |
53 |
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55 | |||
54 | self.entries = [] |
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56 | self.entries = [] | |
55 |
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57 | |||
56 | print "rollback completed" |
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58 | print "rollback completed" | |
57 |
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59 | |||
58 | def recover(self): |
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60 | def recover(self): | |
59 | for l in open(self.journal).readlines(): |
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61 | for l in open(self.journal).readlines(): | |
60 | f, o = l.split('\0') |
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62 | f, o = l.split('\0') | |
61 | self.opener(f, "a").truncate(int(o)) |
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63 | self.opener(f, "a").truncate(int(o)) | |
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64 | os.unlink(self.journal) | |||
62 |
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65 |
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