##// END OF EJS Templates
transaction: __del__ should do nothing if the journal already exists...
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1 # transaction.py - simple journalling scheme for mercurial
1 # transaction.py - simple journalling scheme for mercurial
2 #
2 #
3 # This transaction scheme is intended to gracefully handle program
3 # This transaction scheme is intended to gracefully handle program
4 # errors and interruptions. More serious failures like system crashes
4 # errors and interruptions. More serious failures like system crashes
5 # can be recovered with an fsck-like tool. As the whole repository is
5 # can be recovered with an fsck-like tool. As the whole repository is
6 # effectively log-structured, this should amount to simply truncating
6 # effectively log-structured, this should amount to simply truncating
7 # anything that isn't referenced in the changelog.
7 # anything that isn't referenced in the changelog.
8 #
8 #
9 # Copyright 2005 Matt Mackall <mpm@selenic.com>
9 # Copyright 2005 Matt Mackall <mpm@selenic.com>
10 #
10 #
11 # This software may be used and distributed according to the terms
11 # This software may be used and distributed according to the terms
12 # of the GNU General Public License, incorporated herein by reference.
12 # of the GNU General Public License, incorporated herein by reference.
13
13
14 import os
14 import os
15 import util
15 import util
16
16
17 class transaction:
17 class transaction:
18 def __init__(self, opener, journal, after = None):
18 def __init__(self, opener, journal, after = None):
19 self.journal = None
19 self.journal = None
20
20
21 # abort here if the journal already exists
21 # abort here if the journal already exists
22 if os.path.exists(journal):
22 if os.path.exists(journal):
23 raise "journal already exists - run hg recover"
23 raise "journal already exists - run hg recover"
24
24
25 self.opener = opener
25 self.opener = opener
26 self.after = after
26 self.after = after
27 self.entries = []
27 self.entries = []
28 self.map = {}
28 self.map = {}
29 self.journal = journal
29 self.journal = journal
30
30
31 self.file = open(self.journal, "w")
31 self.file = open(self.journal, "w")
32
32
33 def __del__(self):
33 def __del__(self):
34 if self.entries: self.abort()
34 if self.journal:
35 try: os.unlink(self.journal)
35 if self.entries: self.abort()
36 except: pass
36 self.file.close()
37 try: os.unlink(self.journal)
38 except: pass
37
39
38 def add(self, file, offset):
40 def add(self, file, offset):
39 if file in self.map: return
41 if file in self.map: return
40 self.entries.append((file, offset))
42 self.entries.append((file, offset))
41 self.map[file] = 1
43 self.map[file] = 1
42 # add enough data to the journal to do the truncate
44 # add enough data to the journal to do the truncate
43 self.file.write("%s\0%d\n" % (file, offset))
45 self.file.write("%s\0%d\n" % (file, offset))
44 self.file.flush()
46 self.file.flush()
45
47
46 def close(self):
48 def close(self):
47 self.file.close()
49 self.file.close()
48 self.entries = []
50 self.entries = []
49 if self.after:
51 if self.after:
50 util.rename(self.journal, self.after)
52 util.rename(self.journal, self.after)
51 else:
53 else:
52 os.unlink(self.journal)
54 os.unlink(self.journal)
53
55
54 def abort(self):
56 def abort(self):
55 if not self.entries: return
57 if not self.entries: return
56
58
57 print "transaction abort!"
59 print "transaction abort!"
58
60
59 for f, o in self.entries:
61 for f, o in self.entries:
60 try:
62 try:
61 self.opener(f, "a").truncate(o)
63 self.opener(f, "a").truncate(o)
62 except:
64 except:
63 print "failed to truncate", f
65 print "failed to truncate", f
64
66
65 self.entries = []
67 self.entries = []
66
68
67 print "rollback completed"
69 print "rollback completed"
68
70
69 def rollback(opener, file):
71 def rollback(opener, file):
70 for l in open(file).readlines():
72 for l in open(file).readlines():
71 f, o = l.split('\0')
73 f, o = l.split('\0')
72 opener(f, "a").truncate(int(o))
74 opener(f, "a").truncate(int(o))
73 os.unlink(file)
75 os.unlink(file)
74
76
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