From ef862220a8c474dca9d3c2f92d4afba9bb84bb0d Mon Sep 17 00:00:00 2001
From: Andrew Thompson <andrew@hijacked.us>
Date: Thu, 1 Feb 2018 09:24:57 -0800
Subject: [PATCH] Don't log when we dropped 0 messages

---
 src/error_logger_lager_h.erl | 11 ++++++++---
 src/lager_file_backend.erl   | 17 +++++++++++------
 2 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/src/error_logger_lager_h.erl b/src/error_logger_lager_h.erl
index 3755a1d..a3613e2 100644
--- a/src/error_logger_lager_h.erl
+++ b/src/error_logger_lager_h.erl
@@ -126,9 +126,14 @@ handle_event(Event, #state{sink=Sink, shaper=Shaper} = State) ->
     end.
 
 handle_info({shaper_expired, ?MODULE}, #state{sink=Sink, shaper=Shaper} = State) ->
-    ?LOGFMT(Sink, warning, self(),
-            "lager_error_logger_h dropped ~p messages in the last second that exceeded the limit of ~p messages/sec",
-            [Shaper#lager_shaper.dropped, Shaper#lager_shaper.hwm]),
+    case Shaper#lager_shaper.dropped of
+        0 ->
+            ok;
+        Dropped ->
+            ?LOGFMT(Sink, warning, self(),
+                    "lager_error_logger_h dropped ~p messages in the last second that exceeded the limit of ~p messages/sec",
+                    [Dropped, Shaper#lager_shaper.hwm])
+    end,
     {ok, State#state{shaper=Shaper#lager_shaper{dropped=0, mps=1, lasttime=os:timestamp()}}};
 handle_info(_Info, State) ->
     {ok, State}.
diff --git a/src/lager_file_backend.erl b/src/lager_file_backend.erl
index 1426f18..5dbbcbc 100644
--- a/src/lager_file_backend.erl
+++ b/src/lager_file_backend.erl
@@ -193,12 +193,17 @@ handle_info({rotate, File}, #state{name=File,count=Count,date=Date,rotator=Rotat
     schedule_rotation(File, Date),
     {ok, State1};
 handle_info({shaper_expired, Name}, #state{shaper=Shaper, name=Name, formatter=Formatter, formatter_config=FormatConfig} = State) ->
-    Report = io_lib:format(
-               "lager_file_backend dropped ~p messages in the last second that exceeded the limit of ~p messages/sec",
-               [Shaper#lager_shaper.dropped, Shaper#lager_shaper.hwm]),
-    ReportMsg = lager_msg:new(Report, warning, [], []),
-    write(State, lager_msg:timestamp(ReportMsg),
-          lager_msg:severity_as_int(ReportMsg), Formatter:format(ReportMsg, FormatConfig)),
+    case Shaper#lager_shaper.dropped of
+        0 ->
+            ok;
+        Dropped ->
+            Report = io_lib:format(
+                       "lager_file_backend dropped ~p messages in the last second that exceeded the limit of ~p messages/sec",
+                       [Dropped, Shaper#lager_shaper.hwm]),
+            ReportMsg = lager_msg:new(Report, warning, [], []),
+            write(State, lager_msg:timestamp(ReportMsg),
+                  lager_msg:severity_as_int(ReportMsg), Formatter:format(ReportMsg, FormatConfig))
+    end,
     {ok, State#state{shaper=Shaper#lager_shaper{dropped=0, mps=1, lasttime=os:timestamp()}}};
 handle_info(_Info, State) ->
     {ok, State}.