1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
|
%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 1996-2011. All Rights Reserved.
%%
%% The contents of this file are subject to the Erlang Public License,
%% Version 1.1, (the "License"); you may not use this file except in
%% compliance with the License. You should have received a copy of the
%% Erlang Public License along with this software. If not, it can be
%% retrieved online at http://www.erlang.org/.
%%
%% Software distributed under the License is distributed on an "AS IS"
%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
%% the License for the specific language governing rights and limitations
%% under the License.
%%
%% %CopyrightEnd%
%%
%%
%%-behaviour(mnesia_backup).
%0
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%
%% This module contains one implementation of callback functions
%% used by Mnesia at backup and restore. The user may however
%% write an own module the same interface as mnesia_backup and
%% configure Mnesia so the alternate module performs the actual
%% accesses to the backup media. This means that the user may put
%% the backup on medias that Mnesia does not know about, possibly
%% on hosts where Erlang is not running.
%%
%% The OpaqueData argument is never interpreted by other parts of
%% Mnesia. It is the property of this module. Alternate implementations
%% of this module may have different interpretations of OpaqueData.
%% The OpaqueData argument given to open_write/1 and open_read/1
%% are forwarded directly from the user.
%%
%% All functions must return {ok, NewOpaqueData} or {error, Reason}.
%%
%% The NewOpaqueData arguments returned by backup callback functions will
%% be given as input when the next backup callback function is invoked.
%% If any return value does not match {ok, _} the backup will be aborted.
%%
%% The NewOpaqueData arguments returned by restore callback functions will
%% be given as input when the next restore callback function is invoked
%% If any return value does not match {ok, _} the restore will be aborted.
%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-module(mnesia_backup).
-include_lib("kernel/include/file.hrl").
-export([
%% Write access
open_write/1,
write/2,
commit_write/1,
abort_write/1,
%% Read access
open_read/1,
read/1,
close_read/1
]).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Backup callback interface
-record(backup, {tmp_file, file, file_desc}).
%% Opens backup media for write
%%
%% Returns {ok, OpaqueData} or {error, Reason}
open_write(OpaqueData) ->
File = OpaqueData,
Tmp = lists:concat([File,".BUPTMP"]),
file:delete(Tmp),
file:delete(File),
case disk_log:open([{name, make_ref()},
{file, Tmp},
{repair, false},
{linkto, self()}]) of
{ok, Fd} ->
{ok, #backup{tmp_file = Tmp, file = File, file_desc = Fd}};
{error, Reason} ->
{error, Reason}
end.
%% Writes BackupItems to the backup media
%%
%% Returns {ok, OpaqueData} or {error, Reason}
write(OpaqueData, BackupItems) ->
B = OpaqueData,
case disk_log:log_terms(B#backup.file_desc, BackupItems) of
ok ->
{ok, B};
{error, Reason} ->
abort_write(B),
{error, Reason}
end.
%% Closes the backup media after a successful backup
%%
%% Returns {ok, ReturnValueToUser} or {error, Reason}
commit_write(OpaqueData) ->
B = OpaqueData,
case disk_log:sync(B#backup.file_desc) of
ok ->
case disk_log:close(B#backup.file_desc) of
ok ->
case file:rename(B#backup.tmp_file, B#backup.file) of
ok ->
{ok, B#backup.file};
{error, Reason} ->
{error, Reason}
end;
{error, Reason} ->
{error, Reason}
end;
{error, Reason} ->
{error, Reason}
end.
%% Closes the backup media after an interrupted backup
%%
%% Returns {ok, ReturnValueToUser} or {error, Reason}
abort_write(BackupRef) ->
Res = disk_log:close(BackupRef#backup.file_desc),
file:delete(BackupRef#backup.tmp_file),
case Res of
ok ->
{ok, BackupRef#backup.file};
{error, Reason} ->
{error, Reason}
end.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Restore callback interface
-record(restore, {file, file_desc, cont}).
%% Opens backup media for read
%%
%% Returns {ok, OpaqueData} or {error, Reason}
open_read(OpaqueData) ->
File = OpaqueData,
case file:read_file_info(File) of
{error, Reason} ->
{error, Reason};
_FileInfo -> %% file exists
case disk_log:open([{file, File},
{name, make_ref()},
{repair, false},
{mode, read_only},
{linkto, self()}]) of
{ok, Fd} ->
{ok, #restore{file = File, file_desc = Fd, cont = start}};
{repaired, Fd, _, {badbytes, 0}} ->
{ok, #restore{file = File, file_desc = Fd, cont = start}};
{repaired, Fd, _, _} ->
{ok, #restore{file = File, file_desc = Fd, cont = start}};
{error, Reason} ->
{error, Reason}
end
end.
%% Reads BackupItems from the backup media
%%
%% Returns {ok, OpaqueData, BackupItems} or {error, Reason}
%%
%% BackupItems == [] is interpreted as eof
read(OpaqueData) ->
R = OpaqueData,
Fd = R#restore.file_desc,
case disk_log:chunk(Fd, R#restore.cont) of
{error, Reason} ->
{error, {"Possibly truncated", Reason}};
eof ->
{ok, R, []};
{Cont, []} ->
read(R#restore{cont = Cont});
{Cont, BackupItems, _BadBytes} ->
{ok, R#restore{cont = Cont}, BackupItems};
{Cont, BackupItems} ->
{ok, R#restore{cont = Cont}, BackupItems}
end.
%% Closes the backup media after restore
%%
%% Returns {ok, ReturnValueToUser} or {error, Reason}
close_read(OpaqueData) ->
R = OpaqueData,
case disk_log:close(R#restore.file_desc) of
ok -> {ok, R#restore.file};
{error, Reason} -> {error, Reason}
end.
%0
|
