release_handler.erl

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%% Check that file exists at all masters.
check_file_masters(FileName, Type, [Master|Masters]) ->
    do_check_file(Master, FileName, Type),
    check_file_masters(FileName, Type, Masters);
check_file_masters(_FileName, _Type, []) ->
    ok.

%% Type == regular | directory
do_check_file(FileName, Type) ->
    case file:read_file_info(FileName) of
	{ok, Info} when Info#file_info.type==Type -> ok;
	{error, _Reason} -> throw({error, {no_such_file, FileName}})
    end.

do_check_file(Master, FileName, Type) ->
    case rpc:call(Master, file, file_info, [FileName]) of
	{ok,{_,Type,_,_,_,_,_}} -> ok;
	_ -> throw({error, {no_such_file, {Master, FileName}}})
    end.

%%-----------------------------------------------------------------
%% If Rel doesn't exists in tar it could have been created
%% by the user in another way, i.e. ignore this here.
%%-----------------------------------------------------------------
extract_rel_file(Rel, Tar, Root) ->
    erl_tar:extract(Tar, [{files, [Rel]}, {cwd, Root}, compressed]).

extract_tar(Root, Tar) ->
    case erl_tar:extract(Tar, [keep_old_files, {cwd, Root}, compressed]) of
	ok ->
	    ok;
	{error, Reason, Name} ->		% Old erl_tar.
	    throw({error, {cannot_extract_file, Name, Reason}});
	{error, {Name, Reason}} ->		% New erl_tar (R3A).
	    throw({error, {cannot_extract_file, Name, Reason}})
    end.

write_releases(Dir, NewReleases, false) ->
    case do_write_release(Dir, "RELEASES", NewReleases) of
	ok    -> ok;
	Error -> throw(Error)
    end;
write_releases(Dir, NewReleases, Masters) ->
    all_masters(Masters),
    write_releases_m(Dir, NewReleases, Masters).

do_write_release(Dir, RELEASES, NewReleases) ->
    case file:open(filename:join(Dir, RELEASES), write) of
	{ok, Fd} ->
	    ok = io:format(Fd, "~p.~n", [NewReleases]),
	    file:close(Fd),
	    ok;
	{error, Reason} ->
	    {error, Reason}
    end.

%%-----------------------------------------------------------------
%% Write the "RELEASES" file at all master nodes.
%%   1. Save "RELEASES.backup" at all nodes.
%%   2. Save "RELEASES.change" at all nodes.
%%   3. Update the "RELEASES.change" file at all nodes.
%%   4. Move "RELEASES.change" to "RELEASES".
%%   5. Remove "RELEASES.backup" at all nodes.
%%
%% If one of the steps above fails, all steps is recovered from
%% (as long as possible), except for 5 which is allowed to fail.
%%-----------------------------------------------------------------
write_releases_m(Dir, NewReleases, Masters) ->
    RelFile = filename:join(Dir, "RELEASES"),
    Backup = filename:join(Dir, "RELEASES.backup"),
    Change = filename:join(Dir, "RELEASES.change"),
    ensure_RELEASES_exists(Masters, RelFile),
    case at_all_masters(Masters, ?MODULE, do_copy_files,
			[RelFile, [Backup, Change]]) of
	ok ->
	    case at_all_masters(Masters, ?MODULE, do_write_release,
				[Dir, "RELEASES.change", NewReleases]) of
		ok ->
		    case at_all_masters(Masters, file, rename,
					[Change, RelFile]) of
			ok ->
			    remove_files(all, [Backup, Change], Masters),
			    ok;
			{error, {Master, R}} ->
			    takewhile(Master, Masters, file, rename,
				      [Backup, RelFile]),
			    remove_files(all, [Backup, Change], Masters),
			    throw({error, {Master, R, move_releases}})
		    end;
		{error, {Master, R}} ->
		    remove_files(all, [Backup, Change], Masters),
		    throw({error, {Master, R, update_releases}})
	    end;
	{error, {Master, R}} ->
	    remove_files(Master, [Backup, Change], Masters),
	    throw({error, {Master, R, backup_releases}})
    end.

ensure_RELEASES_exists(Masters, RelFile) ->
    case at_all_masters(Masters, ?MODULE, do_ensure_RELEASES, [RelFile]) of
	ok ->
	    ok;
	{error, {Master, R}} ->
	    throw({error, {Master, R, ensure_RELEASES_exists}})
    end.

copy_file(File, Dir, false) ->
    case do_copy_file(File, Dir) of
	ok    -> ok;
	Error -> throw(Error)
    end;
copy_file(File, Dir, Masters) ->
    all_masters(Masters),
    copy_file_m(File, Dir, Masters).

%%-----------------------------------------------------------------
%% copy File to Dir at every master node.
%% If an error occurs at a node, the total copy failed.
%% We do not have to cleanup in case of failure as this
%% copy_file is harmless.
%%-----------------------------------------------------------------
copy_file_m(File, Dir, [Master|Masters]) ->
    case rpc:call(Master, ?MODULE, do_copy_file, [File, Dir]) of
	ok                   -> copy_file_m(File, Dir, Masters);
	{error, {Reason, F}} -> throw({error, {Master, Reason, F}});
	Other                -> throw({error, {Master, Other, File}})
    end;
copy_file_m(_File, _Dir, []) ->
    ok.

do_copy_file(File, Dir) ->
    File2 = filename:join(Dir, filename:basename(File)),
    do_copy_file1(File, File2).

do_copy_file1(File, File2) ->
    case file:read_file(File) of
	{ok, Bin} ->
	    case file:write_file(File2, Bin) of
		ok -> ok;
		{error, Reason} ->
		    {error, {Reason, File2}}
	    end;
	{error, Reason} ->
	    {error, {Reason, File}}
    end.

%%-----------------------------------------------------------------
%% Copy File to a list of files.
%%-----------------------------------------------------------------
do_copy_files(File, [ToFile|ToFiles]) ->
    case do_copy_file1(File, ToFile) of
	ok    -> do_copy_files(File, ToFiles);
	Error -> Error
    end;
do_copy_files(_, []) ->
    ok.

%%-----------------------------------------------------------------
%% Copy each Src file to Dest file in the list of files.
%%-----------------------------------------------------------------
do_copy_files([{Src, Dest}|Files]) ->
    case do_copy_file1(Src, Dest) of
	ok    -> do_copy_files(Files);
	Error -> Error
    end;
do_copy_files([]) ->
    ok.

%%-----------------------------------------------------------------
%% Rename each Src file to Dest file in the list of files.
%%-----------------------------------------------------------------
do_rename_files([{Src, Dest}|Files]) ->
    case file:rename(Src, Dest) of
	ok    -> do_rename_files(Files);
	Error -> Error
    end;
do_rename_files([]) ->
    ok.

%%-----------------------------------------------------------------
%% Remove a list of files. Ignore failure.
%%-----------------------------------------------------------------
do_remove_files([File|Files]) ->
    file:delete(File),
    do_remove_files(Files);
do_remove_files([]) ->
    ok.


%%-----------------------------------------------------------------
%% Ensure that the RELEASES file exists.
%% If not create an empty RELEASES file.
%%-----------------------------------------------------------------
do_ensure_RELEASES(RelFile) ->
    case file:read_file_info(RelFile) of
	{ok, _} -> ok;
	_       -> do_write_file(RelFile, "[]. ") 
    end.

%%-----------------------------------------------------------------
%% Make a directory, ignore failures (captured later).
%%-----------------------------------------------------------------
make_dir(Dir, false) ->
    file:make_dir(Dir);
make_dir(Dir, Masters) ->
    lists:foreach(fun(Master) -> rpc:call(Master, file, make_dir, [Dir]) end,
		  Masters).

%%-----------------------------------------------------------------
%% Check that all masters are alive.
%%-----------------------------------------------------------------
all_masters(Masters) ->
    case rpc:multicall(Masters, erlang, info, [version]) of
	{_, []}       -> ok;
	{_, BadNodes} -> throw({error, {bad_masters, BadNodes}})
    end.

%%-----------------------------------------------------------------
%% Evaluate {M,F,A} at all masters.
%% {M,F,A} is supposed to return ok. Otherwise at_all_masters
%% returns {error, {Master, Other}}.
%%-----------------------------------------------------------------
at_all_masters([Master|Masters], M, F, A) ->
    case rpc:call(Master, M, F, A) of
	ok    -> at_all_masters(Masters, M, F, A);
	Error -> {error, {Master, Error}}
    end;
at_all_masters([], _, _, _) ->
    ok.

%%-----------------------------------------------------------------
%% Evaluate {M,F,A} at all masters until Master is found.
%% Ignore {M,F,A} return value.
%%-----------------------------------------------------------------
takewhile(Master, Masters, M, F, A) ->
    lists:takewhile(fun(Ma) when Ma == Master ->
			    false;
		       (Ma) ->
			    rpc:call(Ma, M, F, A),
			    true
		    end, Masters),
    ok.

consult(File, false)   -> file:consult(File);
consult(File, Masters) -> consult_master(Masters, File).

%%-----------------------------------------------------------------
%% consult the File at any master node.
%% If the file does not exist at one node it should
%% not exist at any other node either.
%%-----------------------------------------------------------------
consult_master([Master|Ms], File) ->
    case rpc:call(Master, file, consult, [File]) of
	{badrpc, _} -> consult_master(Ms, File);
	Res         -> Res
    end;
consult_master([], _File) ->
    {error, no_master}.

read_file(File, false) ->
    file:read_file(File);
read_file(File, Masters) ->
    read_master(Masters, File).

%% Ignore status of each delete !
remove_files(Master, Files, Masters) ->
    takewhile(Master, Masters, ?MODULE, do_remove_files, [Files]).

%%-----------------------------------------------------------------
%% read the File at any master node.
%% If the file does not exist at one node it should
%% not exist at any other node either.
%%-----------------------------------------------------------------
read_master([Master|Ms], File) ->
    case rpc:call(Master, file, read_file, [File]) of
	{badrpc, _} -> read_master(Ms, File);
	Res         -> Res
    end;
read_master([], _File) ->
    {error, no_master}.

%%-----------------------------------------------------------------
%% Write start_erl.data.
%%-----------------------------------------------------------------
write_start(File, Data, false) ->
    case do_write_file(File, Data) of
	ok    -> ok;
	Error -> throw(Error)
    end;
write_start(File, Data, Masters) ->
    all_masters(Masters),
    write_start_m(File, Data, Masters).


%%-----------------------------------------------------------------
%% Write the "start_erl.data" file at all master nodes.
%%   1. Save "start_erl.backup" at all nodes.
%%   2. Write the "start_erl.change" file at all nodes.
%%   3. Move "start_erl.change" to "start_erl.data".
%%   4. Remove "start_erl.backup" at all nodes.
%%
%% If one of the steps above fails, all steps is recovered from
%% (as long as possible), except for 4 which is allowed to fail.
%%-----------------------------------------------------------------
write_start_m(File, Data, Masters) ->
    Dir = filename:dirname(File),
    Backup = filename:join(Dir, "start_erl.backup"),
    Change = filename:join(Dir, "start_erl.change"),
    case at_all_masters(Masters, ?MODULE, do_copy_files,
			[File, [Backup]]) of
	ok ->
	    case at_all_masters(Masters, ?MODULE, do_write_file,
				[Change, Data]) of
		ok ->
		    case at_all_masters(Masters, file, rename,
					[Change, File]) of
			ok ->
			    remove_files(all, [Backup, Change], Masters),
			    ok;
			{error, {Master, R}} ->
			    takewhile(Master, Masters, file, rename,
				      [Backup, File]),
			    remove_files(all, [Backup, Change], Masters),
			    throw({error, {Master, R, move_start_erl}})
		    end;
		{error, {Master, R}} ->
		    remove_files(all, [Backup, Change], Masters),
		    throw({error, {Master, R, write_start_erl}})
	    end;
	{error, {Master, R}} ->
	    remove_files(Master, [Backup], Masters),
	    throw({error, {Master, R, backup_start_erl}})
    end.

%%-----------------------------------------------------------------
%% Copy the "start.boot" and "sys.config" from SrcDir to DestDir at all
%% master nodes.
%%   1. Save DestDir/"start.backup" and DestDir/"sys.backup" at all nodes.
%%   2. Copy files at all nodes.
%%   3. Remove backup files at all nodes.
%%
%% If one of the steps above fails, all steps is recovered from
%% (as long as possible), except for 3 which is allowed to fail.
%%-----------------------------------------------------------------
set_static_files(SrcDir, DestDir, Masters) ->
    all_masters(Masters),
    Boot = "start.boot",
    Config = "sys.config",
    SrcBoot = filename:join(SrcDir, Boot),
    DestBoot = filename:join(DestDir, Boot),
    BackupBoot = filename:join(DestDir, "start.backup"),
    SrcConf = filename:join(SrcDir, Config),
    DestConf = filename:join(DestDir, Config),
    BackupConf = filename:join(DestDir, "sys.backup"),

    case at_all_masters(Masters, ?MODULE, do_copy_files,
			[[{DestBoot, BackupBoot},
			  {DestConf, BackupConf}]]) of
	ok ->
	    case at_all_masters(Masters, ?MODULE, do_copy_files,
				[[{SrcBoot, DestBoot},
				  {SrcConf, DestConf}]]) of
		ok ->
		    remove_files(all, [BackupBoot, BackupConf], Masters),
		    ok;
		{error, {Master, R}} ->
		    takewhile(Master, Masters, ?MODULE, do_rename_files,
			      [{BackupBoot, DestBoot},
			       {BackupConf, DestConf}]),
		    remove_files(all, [BackupBoot, BackupConf], Masters),
		    throw({error, {Master, R, copy_start_config}})
	    end;
	{error, {Master, R}} ->
	    remove_files(Master, [BackupBoot, BackupConf], Masters),
	    throw({error, {Master, R, backup_start_config}})
    end.