Supervisors and gen_servers

apps/log_monitor/src/coordinator.erl

@@ -1,18 +1,25 @@
 -module(coordinator).
+-behaviour(supervisor).
 -compile(export_all).
 
-start() ->
+start_link() ->
-    _MailerPid = mailer:start(),
+    supervisor:start_link(?MODULE, []).
-    {ok, Files} = application:get_env(log_monitor, logfiles),
-    Monitors = [monitor:start(File) || File <- Files],
-    loop(Monitors).
 
-loop(Monitors) ->
+init([]) ->
-    receive
+    SupFlags = #{strategy => one_for_one},
-        {'EXIT', FromPid, Reason} ->
+    ChildSpecs = [#{
-            io:format("Monitor process terminated: ~s~n", [Reason]),
+                     id => mailer,
-            RemainingMonitors = [M || M <- Monitors, M =/= FromPid],
+                     start => {mailer, start_link, []},
-            loop(RemainingMonitors)
+                     restart => permanent,
-    after 5000 ->
+                     shutdown => 5000
-      loop(Monitors)
+                   }] ++ monitors_child_specs(),
-    end.
+    {ok, {SupFlags, ChildSpecs}}.
+
+monitors_child_specs() ->
+    {ok, Files} = application:get_env(log_monitor, logfiles),
+    [#{
+        id => list_to_atom(File),
+        start => {monitor, start_link, [File]},
+        restart => temporary,
+        shutdown => 5000
+      } || File <- Files].

apps/log_monitor/src/gatherer.erl

@@ -0,0 +1,49 @@
+-module(gatherer).
+-behaviour(gen_server).
+-compile(export_all).
+
+start_link(File) ->
+    gen_server:start_link(?MODULE, [File], []).
+
+init([File]) ->
+    {ok, [off, File]}.
+
+handle_info({log_line, Text}, [off, File]) ->
+    case isError(Text) of
+        true ->
+            {ok, Timer} = timer:send_after(1000, {timeout}),
+            {noreply, [on, File, Text, Timer]};
+        false -> {noreply, [off, File]}
+    end;
+handle_info({log_line, Text}, [on, File, Error, Timer]) ->
+    case isError(Text) of
+        true ->
+            timer:clean(Timer),
+            {ok, NewTimer} = timer:send_after(1000, {timeout}),
+            {noreply, [on, File, Error ++ "\n" ++ Text, NewTimer]};
+        false ->
+            {noreply, [on, File, Error ++ "\n" ++ Text, Timer]}
+    end;
+handle_info({timeout}, [on, File, Error, _Timer]) ->
+    mailer ! {error, File, Error},
+    {noreply, [off, File]}.
+
+handle_cast(_Msg, State) ->
+    {noreply, State}.
+
+handle_call(_Request, _From, State) ->
+    {noreply, State}.
+
+terminate(_Reason, _State) ->
+    shutdown.
+
+code_change(_OldVsn, State, _Extra) ->
+    {ok, State}.
+
+isError(Text) ->
+    case re:run(Text, "ERROR") of %% TODO
+        {match, _} ->
+            true;
+        nomatch ->
+            false
+    end.

apps/log_monitor/src/log_monitor_sup.erl

@@ -29,8 +29,8 @@ start_link() ->
 %% Child :: {Id,StartFunc,Restart,Shutdown,Type,Modules}
 init([]) ->
     {ok, { {one_for_all, 0, 1}, [{console,
-                                  {coordinator, start, []},
+                                  {coordinator, start_link, []},
-                                  permanent, 5000, worker, [monitor]}]} }.
+                                  permanent, 5000, supervisor, [coordinator]}]} }.
 
 %%====================================================================
 %% Internal functions

apps/log_monitor/src/mailer.erl

@@ -1,25 +1,33 @@
 -module(mailer).
+-behaviour(gen_server).
 -compile(export_all).
 
-start() ->
+start_link() ->
-    io:format("Starting Mailer~n", []),
+    gen_server:start_link(?MODULE, [], []).
-    Pid = spawn_link(?MODULE, init, []),
-    register(mailer, Pid),
-    Pid.
 
-init() ->
+init([]) ->
-    loop().
+    register(mailer, self()),
+    {ok, []}.
 
-loop() ->
+handle_info({error, File, Text}, []) ->
-    receive
+    case send_email(File, Text) of
-        {error, File, Text} ->
+        {error, Reason, Message} ->
-            case send_email(File, Text) of
+            io:format("Error sending email: ~s ~p~n", [Reason, Message]);
-              {error, Reason, Message} ->
+        _ -> io:format("Mail sent~n", [])
-                    io:format("Error sending email: ~s ~p~n", [Reason, Message]);
+    end,
-              _ -> io:format("Mail sent~n", [])
+    {noreply, []}.
-            end,
+
-            loop()
+handle_cast(_Msg, State) ->
-    end.
+    {noreply, State}.
+
+handle_call(_Request, _From, State) ->
+    {noreply, State}.
+
+terminate(_Reason, _State) ->
+    shutdown.
+
+code_change(_OldVsn, State, _Extra) ->
+    {ok, State}.
 
 send_email(File, Text) ->
     {ok, EmailConfig} = application:get_env(log_monitor, email_config),

apps/log_monitor/src/monitor.erl

@@ -1,59 +1,22 @@
 -module(monitor).
+-behaviour(supervisor).
 -compile(export_all).
 
-start(File) ->
+start_link(File) ->
-    io:format("Starting monitor for file: ~s~n", [File]),
+    supervisor:start_link(?MODULE, [File]).
-    Pid = spawn_link(?MODULE, init, [File]),
-    Pid.
 
 init(File) ->
-    process_flag(trap_exit, true),
+    SupFlags = #{strategy => one_for_one},
-    startWatcher(File),
+    ChildSpecs = [#{
-    loop(File).
+                     id => gatherer,
-
+                     start => {gatherer, start_link, [File]},
-loop(File) ->
+                     restart => permanent,
-    receive
+                     shutdown => 5000
-        {log_line, Text} ->
+                   },
-            case isError(Text) of
+                  #{
-                true -> errorGathering(File, Text);
+                     id => watcher,
-                false -> loop(File)
+                     start => {watcher, start_link, [self(), File]},
-            end,
+                     restart => permanent,
-            io:format("Received line: ~s~n", [Text]),
+                     shutdown => 5000
-            loop(File);
+                   }],
-        {'EXIT', _FromPid, Reason} ->
+    {ok, {SupFlags, ChildSpecs}}.
-            io:format("Watcher process terminated: ~s~n", [Reason]),
-            startWatcher(File),
-            loop(File)
-    end.
-
-errorGathering(File, Error) ->
-    {ok, Timer} = timer:send_after(1000, {timeout}),
-    errorGathering(File, Error, Timer).
-errorGathering(File, Error, Timer) ->
-    receive
-        {log_line, Text} ->
-            case isError(Text) of
-                true ->
-                    timer:clean(Timer),
-                    {ok, NewTimer} = timer:send_after(1000, {timeout}),
-                    errorGathering(File, Error ++ "\n" ++ Text, NewTimer);
-                false ->
-                    errorGathering(File, Error ++ "\n" ++ Text, Timer)
-            end;
-        {timeout} ->
-            mailer ! {error, File, Error},
-            loop(File)
-    end.
-
-isError(Text) ->
-    case re:run(Text, "ERROR") of %% TODO
-        {match, _} ->
-            true;
-        nomatch ->
-            false
-    end.
-
-startWatcher(File) ->
-    %% WatcherPid = spawn_link(watcher, init, [self(), File]),
-    WatcherPid = watcher:start_link(self(), File),
-    {ok, WatcherPid}.

apps/log_monitor/src/watcher.erl

@@ -2,20 +2,20 @@
 -behaviour(gen_server).
 -compile(export_all).
 
-start_link(MonitorPid, File) ->
+start_link(SupPid, File) ->
-    gen_server:start_link(?MODULE, [MonitorPid, File], []).
+    gen_server:start_link(?MODULE, [SupPid, File], []).
 
-init([MonitorPid, File]) ->
+init([SupPid, File]) ->
-    io:format("Init~n"),
     Cmd = "/usr/bin/tail -n0 --follow=name " ++ File,
     Port = open_port({spawn, Cmd}, [stderr_to_stdout, exit_status, binary]),
-    {ok, [MonitorPid, Port]}.
+    {ok, [SupPid, Port]}.
 
-handle_info(Msg, [MonitorPid, Port]) ->
+handle_info(Msg, [SupPid, Port]) ->
     case Msg of
         {Port, {data, Text}} ->
-            MonitorPid ! {log_line, Text},
+            GathererPid = gatherer_pid(SupPid),
-            {noreply, [MonitorPid, Port]};
+            GathererPid ! {log_line, Text},
+            {noreply, [SupPid, Port]};
         {Port, {exit_status, _Status}} ->
             io:format("Watcher terminated~n"),
             {stop, tail_exit, []}
@@ -27,9 +27,11 @@ handle_cast(_Msg, State) ->
 handle_call(_Request, _From, State) ->
     {noreply, State}.
 
-terminate(Reason, _State) ->
+terminate(_Reason, _State) ->
-    io:format("Reason: ~s~n", [Reason]),
     shutdown.
 
 code_change(_OldVsn, State, _Extra) ->
     {ok, State}.
+
+gatherer_pid(SupPid) ->
+    hd([Pid || {Id, Pid, _, _} <- supervisor:which_children(SupPid), Id == gatherer]).

config/sys.config

@@ -1,7 +1,7 @@
 [
   { log_monitor, 
     [
-      {logfiles, ["/tmp/lines.log"]},
+      {logfiles, ["/tmp/lines.log", "/tmp/lines2.log"]},
       {email_config,
         [
           {sender, "me@example.com"},