深入浅出 Mnesia－schema 创建 (2)

init([]) → 
    ProcLib = [mnesia_monitor, proc_lib], 
    Flags = {one_for_all,0, timer:hours(24)}, % Trust the top supervisor 
    %% 最先启动的是mnesia_monitor 
    %% mnesia_monitor持有mnesia_gvar和mnesia_stats两张ets表 
    %% mnesia的全局变量全都保存在此处 
    Workers = [worker_spec(mnesia_monitor, timer:seconds(3), [gen_server]),
    %% mnesia_subscr 创建订阅管理进程 
    %% 自动将mnesia_event加入到系统订阅表中
    worker_spec(mnesia_subscr, timer:seconds(3), [gen_server]), 
    %% mnesia的锁管理进程 
    worker_spec(mnesia_locker, timer:seconds(3), ProcLib), 
    %% mnesia恢复进程
    worker_spec(mnesia_recover, timer:minutes(3), [gen_server]), 
    %% mnesia事务进程
    worker_spec(mnesia_tm, timer:seconds(30), ProcLib), 
    %% 检察点监控者进程
    supervisor_spec(mnesia_checkpoint_sup), 
    %% snmp监控者进程
    supervisor_spec(mnesia_snmp_sup), 
    %% mnesia主控进程
    worker_spec(mnesia_controller, timer:seconds(3), [gen_server]), 
    %% mnesia数据加载进程 
    worker_spec(mnesia_late_loader, timer:seconds(3), ProcLib) ], 
    {ok,{Flags, Workers}}.

%执行回滚操作
do_fallback_start(true, false) ->
    verbose("Starting from fallback...~n", []),
    %拿到备份文件
    BupFile = fallback_bup(),
    Mod = mnesia_backup,
    %创建一个ets，用来保存本地表
    LocalTabs = ?ets_new_table(mnesia_local_tables, [set, public, {keypos, 2}]),
    case catch iterate(Mod, fun restore_tables/4, BupFile, {start, LocalTabs}) of
        {ok, _Res} ->
            %%  让dets关闭掉schema
            catch dets:close(schema),
            %% 设置临时的文件为schema.TMP
            TmpSchema = mnesia_lib:tab2tmp(schema),
            %% 设置数据文件为schema.DAT
            DatSchema = mnesia_lib:tab2dat(schema),
            %% 得到所有本地表
              AllLT  = ?ets_match_object(LocalTabs, '_'),
            %关闭ets
              ?ets_delete_table(LocalTabs),
            %% schema.TMP重命名为schema.DAT
            case file:rename(TmpSchema, DatSchema) of
                ok ->
                    %% 除了schema表外，全部进行swap操作
                        [(LT#local_tab.swap)(LT#local_tab.name, LT) ||
                             LT <- AllLT, LT#local_tab.name =/= schema],
                    file:delete(BupFile),
                    ok;
                {error, Reason} ->
                    file:delete(TmpSchema),
                    {error, {"Cannot start from fallback. Rename error.", Reason}}
            end;
        {error, Reason} ->
            {error, {"Cannot start from fallback", Reason}};
        {'EXIT', Reason} ->
            {error, {"Cannot start from fallback", Reason}}
    end.