From 62e847acaab5a8ae4c7f1d1c6e9169a95fbb392e Mon Sep 17 00:00:00 2001
From: Luke Bakken <luke@bakken.io>
Date: Thu, 1 Aug 2019 11:57:58 -0700
Subject: [PATCH] Add inode check to write_should_check

---
 src/lager_file_backend.erl | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/lager_file_backend.erl b/src/lager_file_backend.erl
index fdab1b2..862e821 100644
--- a/src/lager_file_backend.erl
+++ b/src/lager_file_backend.erl
@@ -280,15 +280,18 @@ write(#state{name=Name, fd=FD,
 write_should_check(#state{fd=undefined}, _Timestamp) ->
     true;
 write_should_check(#state{last_check=LastCheck0, check_interval=CheckInterval,
-                          name=Name, ctime=Ctime0}, Timestamp) ->
+                          name=Name, inode=Inode0, ctime=Ctime0}, Timestamp) ->
     LastCheck1 = timer:now_diff(Timestamp, LastCheck0) div 1000,
     case LastCheck1 >= CheckInterval of
         true ->
             true;
         _ ->
+            % TODO this code is duplicated in the default rotator, but we need
+            % to know if the file has changed "out from under lager" so we don't
+            % write to an invalid FD
             case file:read_file_info(Name, [raw]) of
-                {ok, #file_info{ctime=Ctime1}} ->
-                    Ctime0 =/= Ctime1;
+                {ok, #file_info{inode=Inode1, ctime=Ctime1}} ->
+                    Inode0 =/= Inode1 orelse Ctime0 =/= Ctime1;
                 _ ->
                     true
             end