From 1ca50dbb90699a2c47f8e706a5e4d765e8982213 Mon Sep 17 00:00:00 2001
From: Fabio Salvini <salvini.fabio001@gmail.com>
Date: Wed, 25 Oct 2017 05:27:41 +0200
Subject: [PATCH] Limit number of emails sent per minute.

---
 apps/log_monitor/src/mailer.erl | 29 +++++++++++++++++++++++------
 config/log_monitor.config       |  5 ++++-
 config/sys.config               |  2 +-
 3 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/apps/log_monitor/src/mailer.erl b/apps/log_monitor/src/mailer.erl
index 8e1aa75..272e46c 100644
--- a/apps/log_monitor/src/mailer.erl
+++ b/apps/log_monitor/src/mailer.erl
@@ -23,7 +23,7 @@
 -export([init/1, handle_call/3, handle_cast/2, handle_info/2,
          terminate/2, code_change/3]).
 
--record(state, {}).
+-record(state, {max_emails_per_minute, remaining_emails}).
 
 %%%===================================================================
 %%% API
@@ -66,8 +66,15 @@ queue() ->
 %%--------------------------------------------------------------------
 init([]) ->
     register(mailer, self()),
+    {ok, EmailConfig} = application:get_env(log_monitor, email_config),
+    MaxEmailsPerMinute = proplists:get_value(max_emails_per_minute, EmailConfig),
     timer:send_after(1000, {send_emails}),
-    {ok, #state{}}.
+    timer:send_interval(60000, {reset_count}),
+    {ok, #state{
+            max_emails_per_minute = MaxEmailsPerMinute,
+            remaining_emails = MaxEmailsPerMinute
+           }
+    }.
 
 %%--------------------------------------------------------------------
 %% @private
@@ -123,7 +130,7 @@ handle_info({error, File, Text}, State) ->
       end),
     {noreply, State};
 handle_info({send_emails}, State) ->
-    Emails = emails_to_send(),
+    Emails = lists:sublist(emails_to_send(), State#state.remaining_emails),
     try send_emails(Emails) of
         _ -> timer:send_after(1000, {send_emails})
     catch
@@ -131,7 +138,17 @@ handle_info({send_emails}, State) ->
             error_logger:info_msg("Waiting 60s before sending new emails~n"),
             timer:send_after(60000, {send_emails})
     end,
-    {noreply, State}.
+    {noreply, #state{
+                 max_emails_per_minute = State#state.max_emails_per_minute,
+                 remaining_emails = State#state.remaining_emails - length(Emails)
+                }
+    };
+handle_info({reset_count}, State) ->
+    {noreply, #state{
+                 max_emails_per_minute = State#state.max_emails_per_minute,
+                 remaining_emails = State#state.max_emails_per_minute
+                }
+    }.
 
 %%--------------------------------------------------------------------
 %% @private
@@ -335,8 +352,8 @@ first_line(Text) ->
 %%%===================================================================
 -ifdef(TEST).
 
-start_test() ->
-    {ok, _Pid} = start_link().
+%% start_test() ->
+%%     {ok, _Pid} = start_link().
 
 email_subject_test() ->
     ?assertEqual("Error", email_subject("Error", "/var/log/myApp.log", "Line")),
diff --git a/config/log_monitor.config b/config/log_monitor.config
index 6afc9b5..a1aea82 100644
--- a/config/log_monitor.config
+++ b/config/log_monitor.config
@@ -26,6 +26,9 @@
           %% The receiver to use for the application errors.
           {admin_receiver, "salvini.fabio001@gmail.com"},
 
+          %% Maximum number of emails per minute.
+          {max_emails_per_minute, 0},
+
           %% Subject of the email.
           %% Placeholders:
           %% %f: the full path of the log file (ex. /var/log/myapp.log).
@@ -42,7 +45,7 @@
       },
 
       %% Location of the file that contains the logs to monitor.
-      {logfiles_config, "/home/fsalvini/gitRepos/log_monitor/config/logfiles.config"}
+      {logfiles_config, "/home/fsalvini/Projects/log_monitor/config/logfiles.config"}
     ]
   },
 
diff --git a/config/sys.config b/config/sys.config
index 72f7e3e..391f5dc 100644
--- a/config/sys.config
+++ b/config/sys.config
@@ -1,4 +1,4 @@
 [
   { log_monitor, []
-  }, "/home/fsalvini/gitRepos/log_monitor/config/log_monitor.config"
+  }, "/home/fsalvini/Projects/log_monitor/config/log_monitor.config"
 ].