Fix synchronization in LocalCheckpointTracker#contains (#38755)

dnhatn · web-flow · commit 90e6fb0a56a4 · 2019-02-12T11:06:22.000-05:00
We are accessing the `CountedBitSet` in `LocalCheckpointTracker#contains` without proper synchronization. Relates #33871
diff --git 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 boolean contains(final long seqNo) {
             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));
     }
 
     /**

Original file line number	Diff line number	Diff line change
`@@ -157,11 +157,11 @@ public boolean contains(final long seqNo) {`
`157`	`157`	`return true;`
`158`	`158`	`}`
`159`	`159`	`final long bitSetKey = getBitSetKey(seqNo);`
`160`		`- final CountedBitSet bitSet;`
	`160`	`+ final int bitSetOffset = seqNoToBitSetOffset(seqNo);`
`161`	`161`	`synchronized (this) {`
`162`		`- bitSet = processedSeqNo.get(bitSetKey);`
	`162`	`+ final CountedBitSet bitSet = processedSeqNo.get(bitSetKey);`
	`163`	`+ return bitSet != null && bitSet.get(bitSetOffset);`
`163`	`164`	`}`
`164`		`- return bitSet != null && bitSet.get(seqNoToBitSetOffset(seqNo));`
`165`	`165`	`}`
`166`	`166`
`167`	`167`	`/**`