From 990cbea50dcec97774d75432d08e702f4c0888da Mon Sep 17 00:00:00 2001
From: abicky <takeshi.arabiki@gmail.com>
Date: Mon, 23 Oct 2017 15:45:07 +0900
Subject: [PATCH] Lock the buffer during selecting metadata

cf. https://github.com/fluent/fluentd/pull/1721#discussion_r146176074
---
 lib/fluent/plugin/buffer.rb | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/lib/fluent/plugin/buffer.rb b/lib/fluent/plugin/buffer.rb
index 337b3b79c8..61a904eda6 100644
--- a/lib/fluent/plugin/buffer.rb
+++ b/lib/fluent/plugin/buffer.rb
@@ -351,11 +351,15 @@ def enqueue_unstaged_chunk(chunk)
       def enqueue_all
         log.trace "enqueueing all chunks in buffer", instance: self.object_id
         if block_given?
-          synchronize{ @stage.keys }.each do |metadata|
-            chunk = @stage[metadata]
-            next unless chunk
-            v = yield metadata, chunk
-            enqueue_chunk(metadata) if v
+          metadata_array = []
+          synchronize do
+            @stage.each do |metadata, chunk|
+              v = yield metadata, chunk
+              metadata_array << metadata if v
+            end
+          end
+          metadata_array.each do |metadata|
+            enqueue_chunk(metadata)
           end
         else
           synchronize{ @stage.keys }.each do |metadata|