Merge pull request #57 from heroku/no_tail_warning

Adds L20 - tail session forbidden message.

src/logplex.app.src

@@ -42,6 +42,9 @@
     ,{logplex_shard_urls, "redis://localhost:6379"}
     ,{max_drains_per_channel, 5} % #channels
     ,{metrics_namespace, "dev"} % string, no spaces
+    ,{no_tail_warning,
+      "Error L20 (Tail sessions forbidden) "
+      "Tail sessions for this app are forbidden due to log volume."} % string
     ,{pagerduty, "0"} % "0" = disabled
     ,{queue_length, 2000}
     ,{redgrid_redis_url, "redis://localhost:6379"}

src/logplex_api.erl

@@ -273,6 +273,7 @@ handlers() ->
             {tail_not_requested, _} ->
                 end_chunked_response(Socket);
             {_, no_tail} ->
+                gen_tcp:send(Socket, no_tail_warning()),
                 end_chunked_response(Socket);
             _ ->
                 ?INFO("at=tail_start channel_id=~p filters=~100p",
@@ -547,6 +548,12 @@ filter_and_send_chunked_logs(Resp, [Msg|Tail], Filters, Num, Acc) ->
     end.
 
 
+no_tail_warning() ->
+    logplex_utils:format(undefined,
+                         logplex_utils:formatted_utc_date(),
+                         <<"Logplex">>,
+                         logplex_app:config(no_tail_warning)).
+
 tail_init(Socket, Buffer, Filters, ChannelId) ->
     inet:setopts(Socket, [{active, once}]),
     tail_loop(Socket, Buffer, Filters, ChannelId, 0).

src/logplex_utils.erl

@@ -23,6 +23,7 @@
 -module(logplex_utils).
 -export([rpc/4, set_weight/1, resolve_host/1,
          parse_msg/1, filter/2, formatted_utc_date/0, format/1, field_val/2, field_val/3,
+         format/4,
          parse_redis_url/1, nl/1, to_int/1]).
 
 -include("logplex.hrl").
@@ -78,17 +79,19 @@ formatted_utc_date() ->
     DateFormat = fun(Int) -> string:right(integer_to_list(Int), 2, $0) end,
     io_lib:format("~w-~s-~sT~s:~s:~s-~s:00", [Year, DateFormat(Month), DateFormat(Day), DateFormat(Hour), DateFormat(Min), DateFormat(Sec), DateFormat(Offset)]).
 
-format(Msg) when is_record(Msg, msg) ->
-    Ps =
-        case Msg#msg.ps of
+format(#msg{ps = Ps, time = Time, source = Source, content = Content}) ->
+    format(Ps, Time, Source, Content);
+format(_Msg) ->
+    "".
+
+format(Ps, Time, Source, Content) ->
+    Ps1 =
+        case Ps of
             undefined -> <<>>;
-            _ -> [<<"[">>, Msg#msg.ps, <<"]">>]
+            _ -> [<<"[">>, Ps, <<"]">>]
         end,
-    iolist_to_binary([Msg#msg.time, <<" ">>, Msg#msg.source, Ps, <<": ">>,
-                      nl(Msg#msg.content)]);
+    iolist_to_binary([Time, <<" ">>, Source, Ps1, <<": ">>, nl(Content)]).
 
-format(_Msg) ->
-    "".
 
 -spec nl(iolist() | binary()) -> iolist().
 nl(<<>>) -> <<"\n">>;