move reporters configuration to app.config file

The idea here is to allow using all available exomoter options - we can do this
by specifing them in the app.config file. User can start as many reporterts as
it want and mim just iterates over active reporters and adds subscripions for
them

apps/ejabberd/src/ejabberd_app.erl

@@ -247,27 +247,16 @@ init_metrics() ->
         fun(Host) ->
             mongoose_metrics:init_predefined_host_metrics(Host)
         end, ?MYHOSTS),
-    ReporterOpts = ejabberd_config:get_local_option(metrics_reporter),
-    maybe_start_reporter(ReporterOpts).
-
-maybe_start_reporter(undefined) ->
-    ok;
-maybe_start_reporter(Opts) ->
-    Interval = proplists:get_value(interval, Opts, 5000),
-    case proplists:get_value(backend, Opts) of
-        graphite ->
-            Host = proplists:get_value(host, Opts, "localhost"),
-            R = mongoose_metrics:start_graphite_reporter(Host),
-            start_subscriptions(R, Interval);
-        _ ->
-            undefined
-    end.
+    Reporters = exometer_report:list_reporters(),
+    lists:foreach(
+        fun({Name, _Reporter}) ->
+                Interval = application:get_env(exometer, mongooseim_interval, 5000),
+                start_subscriptions(Name, Interval)
+        end, Reporters).
 
-start_subscriptions({ok, Reporter}, Interval) ->
+start_subscriptions(Reporter, Interval) ->
     mongoose_metrics:start_global_metrics_subscriptions(Reporter, Interval),
     lists:foreach(
       fun(Host) ->
               mongoose_metrics:start_host_metrics_subscriptions(Reporter, Host, Interval)
-      end, ?MYHOSTS);
-start_subscriptions(Error, _Interval) ->
-    ?ERROR_MSG("cannot start exometer reporter: ~p", [Error]).
+      end, ?MYHOSTS).

rel/files/app.config

@@ -6,6 +6,20 @@
         {lager_file_backend, [{file, "log/ejabberd.log"}, {level, info}, {size, 2097152}, {date, "$D0"}, {count, 5}]}
     ]}
   ]}
+%{exometer, [
+%    {mongooseim_interval, 6000},
+%    {report, [
+%        {reporters, [
+%                     {exometer_report_graphite, [
+%                                                 {prefix, "mongosoeim"},
+%                                                 {connect_timeout, 5000},
+%                                                 {host, "127.0.0.1"},
+%                                                 {port, 2003},
+%                                                 {api_key, ""}
+%                                                ]}
+%                    ]}
+%    ]}
+%  ]}
 ].
 
 %% vim: filetype=erlang

rel/files/ejabberd.cfg

@@ -286,7 +286,6 @@
 %%{sm_backend, {redis, [{pool_size, 3}, {worker_config, [{host, "localhost"}, {port, 6379}]}]}}.
 {sm_backend, {{sm_backend}} }.
 
-%{metrics_reporter, [{backend, graphite}, {interval, 5000}, {host, "127.0.0.1"}]}.
 
 %%%.   ==============
 %%%'   AUTHENTICATION