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authorErlang/OTP <[email protected]>2009-11-20 14:54:40 +0000
committerErlang/OTP <[email protected]>2009-11-20 14:54:40 +0000
commit84adefa331c4159d432d22840663c38f155cd4c1 (patch)
treebff9a9c66adda4df2106dfd0e5c053ab182a12bd /lib/mnesia/src/mnesia_backup.erl
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The R13B03 release.OTP_R13B03
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+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 1996-2009. 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
+