Merge pull request #1957 from abicky/resolve-unexpected-exist-on-sigusr1

Resolve unexpected exit on SIGUSR1

lib/fluent/log.rb

@@ -625,5 +625,12 @@ def sync=(v)
         super
       end
     end
+
+    def reopen(path, mode)
+      if mode != 'a'
+        raise "Unsupported mode: #{mode}"
+      end
+      super(path)
+    end
   end
 end

lib/fluent/supervisor.rb

@@ -180,7 +180,11 @@ def supervisor_sighup_handler
 
     def supervisor_sigusr1_handler
       if log = config[:logger_initializer]
-        log.reopen!
+        # Creating new thread due to mutex can't lock
+        # in main thread during trap context
+        Thread.new {
+          log.reopen!
+        }.run
       end
 
       if config[:worker_pid]
@@ -685,14 +689,13 @@ def install_main_process_signal_handlers
     end
 
     def flush_buffer
-      $log.debug "fluentd main process get SIGUSR1"
-      $log.info "force flushing buffered events"
-      @log.reopen!
-
       # Creating new thread due to mutex can't lock
       # in main thread during trap context
       Thread.new {
         begin
+          $log.debug "fluentd main process get SIGUSR1"
+          $log.info "force flushing buffered events"
+          @log.reopen!
           Fluent::Engine.flush!
           $log.debug "flushing thread: flushed"
         rescue Exception => e