From eca54045729d7b660d7eda1f4abf083a6dd1df1d Mon Sep 17 00:00:00 2001
From: Nhat Nguyen <nhat.nguyen@elastic.co>
Date: Tue, 12 Feb 2019 11:06:22 -0500
Subject: [PATCH] Fix synchronization in LocalCheckpointTracker#contains
 (#38755)

We are accessing the `CountedBitSet` in `LocalCheckpointTracker#contains`
without proper synchronization.

Relates #33871
---
 .../elasticsearch/index/seqno/LocalCheckpointTracker.java   | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/server/src/main/java/org/elasticsearch/index/seqno/LocalCheckpointTracker.java b/server/src/main/java/org/elasticsearch/index/seqno/LocalCheckpointTracker.java
index 8249e2600ad..50f4e311c8d 100644
--- a/server/src/main/java/org/elasticsearch/index/seqno/LocalCheckpointTracker.java
+++ b/server/src/main/java/org/elasticsearch/index/seqno/LocalCheckpointTracker.java
@@ -157,11 +157,11 @@ public class LocalCheckpointTracker {
             return true;
         }
         final long bitSetKey = getBitSetKey(seqNo);
-        final CountedBitSet bitSet;
+        final int bitSetOffset = seqNoToBitSetOffset(seqNo);
         synchronized (this) {
-            bitSet = processedSeqNo.get(bitSetKey);
+            final CountedBitSet bitSet = processedSeqNo.get(bitSetKey);
+            return bitSet != null && bitSet.get(bitSetOffset);
         }
-        return bitSet != null && bitSet.get(seqNoToBitSetOffset(seqNo));
     }
 
     /**