Use Mnesia to store monitored log files

apps/log_monitor/src/config.erl

@@ -1,31 +1,43 @@
 -module(config).
 -behaviour(gen_server).
 
--export([monitor_log/2, unmonitor_log/1]).
+-export([create_group/2, monitor_log/3, unmonitor_log/1]).
 -export([logfiles/0]).
 -export([start_link/0, init/1, terminate/2]).
 -export([handle_info/2, handle_cast/2, handle_call/3]).
 -export([code_change/3]).
 
+-record(state, {statuses}).
+
+%% Mnesia tables
+-record(log_monitor_group, {name, email_receivers=[]}).
+-record(log_monitor_file, {file, error_regex, status, group}).
+
 start_link() ->
     gen_server:start_link(?MODULE, [], []).
 
 init([]) ->
     register(config, self()),
-    {ok, Storage} = application:get_env(log_monitor, storage),
-    {ok, Logfiles} = dets:open_file(Storage, [{auto_save, 1000}]),
     Statuses = ets:new(log_statuses, []),
-    lists:foreach(fun({File, ErrorRegex}) ->
-                          ets:insert(Statuses, {File, disabled}),
-                          logfiles_sup:add_child([File, ErrorRegex])
-                  end, dets:foldl(fun(X, L) -> [X|L] end, [], Logfiles)),
-    {ok, [Logfiles, Statuses]}.
+    start_mnesia(),
+    mnesia:activity(
+      transaction,
+      fun() ->
+              mnesia:foldl(
+                fun(#log_monitor_file{file = File, error_regex = ErrorRegex}, _Acc) ->
+                        ets:insert(Statuses, {File, inactive}),
+                        logfiles_sup:add_child([File, ErrorRegex]),
+                        ok
+                end, [], log_monitor_file)
+      end),
+    {ok, #state{statuses = Statuses}}.
 
-handle_info({watcher_init, File}, State = [_Logfiles, Statuses]) ->
-    ets:insert(Statuses, {File, enabled}),
+handle_info({watcher_init, File}, State = #state{statuses = Statuses}) ->
+    ets:insert(Statuses, {File, active}),
     {noreply, State};
-handle_info({watcher_terminate, File}, State = [_Logfiles, Statuses]) ->
-    ets:insert(Statuses, {File, disabled}),
+handle_info({watcher_terminate, File}, State = #state{statuses = Statuses}) ->
+    %% TODO: do not update it if not present
+    ets:insert(Statuses, {File, inactive}),
     {noreply, State};
 handle_info(_Msg, State) ->
     {noreply, State}.
@@ -33,21 +45,51 @@ handle_info(_Msg, State) ->
 handle_cast(_Msg, State) ->
     {noreply, State}.
 
-handle_call({monitor, File, ErrorRegex}, _From, State = [Logfiles, Statuses]) ->
-    case dets:lookup(Logfiles, File) of
+handle_call({create_group, Name, EmailReceivers}, _From, State) ->
+    mnesia:activity(
+      transaction,
+      fun() ->
+              case mnesia:read(log_monitor_group, Name) of
                   [] ->
-            dets:insert(Logfiles, {File, ErrorRegex}),
-            ets:insert(Statuses, {File, disabled}),
+                      mnesia:write(#log_monitor_group{name = Name, email_receivers = EmailReceivers}),
+                      {reply, ok, State};
+                  _ -> {reply, {error, "Duplicate"}, State}
+              end
+      end);
+handle_call({monitor, Group, File, ErrorRegex}, _From, State) ->
+    mnesia:activity(
+      transaction,
+      fun() ->
+              case mnesia:read(log_monitor_group, Group) of
+                  [{log_monitor_group, Group, _}] ->
+                      case mnesia:read(log_monitor_file, File) of
+                          [] ->
+                              mnesia:write(#log_monitor_file{
+                                              file = File,
+                                              error_regex = ErrorRegex,
+                                              group = Group,
+                                              status = enabled}),
                               logfiles_sup:add_child([File, ErrorRegex]),
                               {reply, ok, State};
-        _ -> {reply, duplicate, State}
+                          _ -> {reply, {error, "Duplicate"}, State}
                       end;
-handle_call({unmonitor, File}, _From, State = [Logfiles, Statuses]) ->
-    logfiles_sup:remove_child(File),
+                  [] -> {reply, {error, "Unknown group"}, State}
+              end
+      end);
+handle_call({unmonitor, File}, _From, State = #state{statuses = Statuses}) ->
+    mnesia:activity(
+      transaction,
+      fun() ->
+              case mnesia:read(log_monitor_file, File) of
+                  [{log_monitor_file, File, _, _, _}] ->
+                      mnesia:delete({log_monitor_file, File}),
                       ets:delete(Statuses, File),
-    dets:delete(Logfiles, File),
+                      logfiles_sup:remove_child(File),
                       {reply, ok, State};
-handle_call({get_statuses}, _From, State = [_Logfiles, Statuses]) ->
+                  _ -> {reply, {error, "File not found"}, State}
+              end
+      end);
+handle_call({get_statuses}, _From, State = #state{statuses = Statuses}) ->
     {reply, ets:tab2list(Statuses), State}.
 
 terminate(_Reason, _State) ->
@@ -56,11 +98,33 @@ terminate(_Reason, _State) ->
 code_change(_OldVsn, State, _Extra) ->
     {ok, State}.
 
-monitor_log(File, ErrorRegex) ->
-    gen_server:call(config, {monitor, File, ErrorRegex}).
+create_group(Name, EmailReceivers) ->
+    gen_server:call(config, {create_group, Name, EmailReceivers}).
+
+monitor_log(Group, File, ErrorRegex) ->
+    gen_server:call(config, {monitor, Group, File, ErrorRegex}).
 
 unmonitor_log(File) ->
     gen_server:call(config, {unmonitor, File}).
 
 logfiles() ->
     gen_server:call(config, {get_statuses}).
+
+start_mnesia() ->
+    Nodes = [node()],
+    %% Stop Mnesia if is running, cannot create schema otherwise.
+    mnesia:stop(),
+    mnesia:create_schema(Nodes),
+    mnesia:start(),
+    mnesia:create_table(log_monitor_group,
+                        [
+                         {attributes, record_info(fields, log_monitor_group)},
+                         {disc_copies, Nodes}
+                        ]),
+    mnesia:create_table(log_monitor_file,
+                        [
+                         {attributes, record_info(fields, log_monitor_file)},
+                         {index, [#log_monitor_file.group]},
+                         {disc_copies, Nodes}
+                        ]),
+    ok = mnesia:wait_for_tables([log_monitor_group, log_monitor_file], 30000).

apps/log_monitor/src/log_monitor.app.src

@@ -6,7 +6,8 @@
   {applications,
    [kernel,
     stdlib,
-    gen_smtp
+    gen_smtp,
+    mnesia
    ]},
   {env,[]},
   {modules, []},

config/log_monitor.config

@@ -1,9 +1,6 @@
 [
   { log_monitor, 
     [
-      %% File where the list of monitored log files is stored.
-      %% WARNING: If you leave it inside /tmp, every time the node is restarted the log files will be lost.
-      {storage, "/tmp/logfiles"},
       {email_config,
         [
           {sender, "log@monitor.com"},
@@ -16,5 +13,12 @@
         ]
       }
     ]
+  },
+  %% Directory where the application data is stored.
+  %% WARNING: If you leave it inside /tmp, every time the node is restarted the
+  %% application will reset.
+  { mnesia , [
+      {dir, "/tmp/mnesia"}
+    ]
   }
 ].