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Diffstat (limited to 'lib/mnesia/src/mnesia_backup.erl')
| -rw-r--r-- | lib/mnesia/src/mnesia_backup.erl | 201 |
1 files changed, 201 insertions, 0 deletions
diff --git a/lib/mnesia/src/mnesia_backup.erl b/lib/mnesia/src/mnesia_backup.erl new file mode 100644 index 0000000000..f372ca0be5 --- /dev/null +++ b/lib/mnesia/src/mnesia_backup.erl @@ -0,0 +1,201 @@ +%% +%% %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 + |