From 810b6c0adaeac25c1842f2796c459102f8b70e55 Mon Sep 17 00:00:00 2001
From: Fabio Salvini <salvini.fabio001@gmail.com>
Date: Mon, 12 Jun 2017 14:27:21 +0200
Subject: [PATCH] Error regex as external parameter and monitoring

---
 apps/log_monitor/src/config.erl   | 39 ++++++++++++++++++-------------
 apps/log_monitor/src/gatherer.erl |  6 ++---
 apps/log_monitor/src/log_sup.erl  | 10 ++++----
 apps/log_monitor/src/watcher.erl  | 12 ++++++----
 4 files changed, 37 insertions(+), 30 deletions(-)

diff --git a/apps/log_monitor/src/config.erl b/apps/log_monitor/src/config.erl
index 41dce6e..c73e438 100644
--- a/apps/log_monitor/src/config.erl
+++ b/apps/log_monitor/src/config.erl
@@ -1,13 +1,12 @@
 -module(config).
 -behaviour(gen_server).
 
--export([monitor_log/1]).
+-export([monitor_log/2]).
+-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]).
 
--define(INTERVAL, 60000). % One minute
-
 start_link() ->
     gen_server:start_link(?MODULE, [], []).
 
@@ -15,11 +14,14 @@ init([]) ->
     register(config, self()),
     {ok, Storage} = application:get_env(log_monitor, storage),
     {ok, Logfiles} = dets:open_file(Storage, []),
-    %% erlang:send_after(?INTERVAL, self(), trigger),
-    {ok, [Logfiles]}.
+    Statuses = ets:new(log_statuses, []),
+    {ok, [Logfiles, Statuses]}.
 
-handle_info(trigger, State) ->
-    erlang:send_after(?INTERVAL, self(), trigger),
+handle_info({watcher_init, File}, State = [_Logfiles, Statuses]) ->
+    ets:insert(Statuses, {File, enabled}),
+    {noreply, State};
+handle_info({watcher_terminate, File}, State = [_Logfiles, Statuses]) ->
+    ets:insert(Statuses, {File, disabled}),
     {noreply, State};
 handle_info(_Msg, State) ->
     {noreply, State}.
@@ -27,14 +29,17 @@ handle_info(_Msg, State) ->
 handle_cast(_Msg, State) ->
     {noreply, State}.
 
-handle_call({monitor, File}, _From, [Logfiles]) ->
+handle_call({monitor, File, ErrorRegex}, _From, State = [Logfiles, Statuses]) ->
     case dets:lookup(Logfiles, File) of
         [] ->
-            dets:insert(Logfiles, {File, "ERROR"}),
-            supervisor:start_child(logfiles_sup, [File]),
-            {reply, ok, [Logfiles]};
-        _ -> {reply, duplicate, [Logfiles]}
-    end.
+            dets:insert(Logfiles, {File, ErrorRegex}),
+            ets:insert(Statuses, {File, disabled}),
+            supervisor:start_child(logfiles_sup, [File, ErrorRegex]),
+            {reply, ok, State};
+        _ -> {reply, duplicate, State}
+    end;
+handle_call({get_statuses}, _From, State = [_Logfiles, Statuses]) ->
+    {reply, ets:tab2list(Statuses), State}.
 
 terminate(_Reason, _State) ->
     shutdown.
@@ -42,6 +47,8 @@ terminate(_Reason, _State) ->
 code_change(_OldVsn, State, _Extra) ->
     {ok, State}.
 
-monitor_log(File) ->
-    config ! {monitor, File},
-    gen_server:call(config, {monitor, File}).
+monitor_log(File, ErrorRegex) ->
+    gen_server:call(config, {monitor, File, ErrorRegex}).
+
+logfiles() ->
+    gen_server:call(config, {get_statuses}).
diff --git a/apps/log_monitor/src/gatherer.erl b/apps/log_monitor/src/gatherer.erl
index 2273cd6..c28e21b 100644
--- a/apps/log_monitor/src/gatherer.erl
+++ b/apps/log_monitor/src/gatherer.erl
@@ -1,15 +1,13 @@
 -module(gatherer).
 -behaviour(gen_server).
 
--export([start_link/1, init/1, terminate/2]).
+-export([start_link/2, init/1, terminate/2]).
 -export([handle_info/2, handle_cast/2, handle_call/3]).
 -export([code_change/3]).
 
 -record(log, {file, error_regex}).
 
-%% start_link(File, ErrorRegex) ->
-start_link(File) ->
-    ErrorRegex = "ERROR",
+start_link(File, ErrorRegex) ->
     gen_server:start_link(?MODULE, [#log{file = File, error_regex = ErrorRegex}], []).
 
 init([Log]) ->
diff --git a/apps/log_monitor/src/log_sup.erl b/apps/log_monitor/src/log_sup.erl
index 9ae6824..8c1c2b0 100644
--- a/apps/log_monitor/src/log_sup.erl
+++ b/apps/log_monitor/src/log_sup.erl
@@ -1,17 +1,17 @@
 -module(log_sup).
 -behaviour(supervisor).
 
--export([start_link/1]).
+-export([start_link/2]).
 -export([init/1]).
 
-start_link(File) ->
-    supervisor:start_link(?MODULE, [File]).
+start_link(File, ErrorRegex) ->
+    supervisor:start_link(?MODULE, [File, ErrorRegex]).
 
-init(File) ->
+init([File, ErrorRegex]) ->
     SupFlags = #{strategy => one_for_one},
     ChildSpecs = [#{
                      id => gatherer,
-                     start => {gatherer, start_link, [File]},
+                     start => {gatherer, start_link, [File, ErrorRegex]},
                      restart => permanent,
                      shutdown => 5000
                    },
diff --git a/apps/log_monitor/src/watcher.erl b/apps/log_monitor/src/watcher.erl
index a6eb18b..a7af2c9 100644
--- a/apps/log_monitor/src/watcher.erl
+++ b/apps/log_monitor/src/watcher.erl
@@ -10,18 +10,19 @@ start_link(SupPid, File) ->
 
 init([SupPid, File]) ->
     timer:sleep(1000),
+    config ! {watcher_init, File},
     Cmd = "/usr/bin/tail -n0 --follow=name " ++ File,
     Port = open_port({spawn, Cmd}, [stderr_to_stdout, exit_status, binary]),
-    {ok, [SupPid, Port]}.
+    {ok, [File, SupPid, Port]}.
 
-handle_info(Msg, [SupPid, Port]) ->
+handle_info(Msg, [File, SupPid, Port]) ->
     case Msg of
         {Port, {data, Text}} ->
             GathererPid = gatherer_pid(SupPid),
             GathererPid ! {log_line, Text},
-            {noreply, [SupPid, Port]};
+            {noreply, [File, SupPid, Port]};
         {Port, {exit_status, _Status}} ->
-            {stop, tail_exit, []}
+            {stop, tail_exit, [File]}
     end.
 
 handle_cast(_Msg, State) ->
@@ -30,7 +31,8 @@ handle_cast(_Msg, State) ->
 handle_call(_Request, _From, State) ->
     {noreply, State}.
 
-terminate(_Reason, _State) ->
+terminate(_Reason, [File]) ->
+    config ! {watcher_terminate, File},
     shutdown.
 
 code_change(_OldVsn, State, _Extra) ->