From d1848b96fc5943f68cfecb1e2f1c9e02734edf06 Mon Sep 17 00:00:00 2001
From: David Roberts <dave.roberts@elastic.co>
Date: Mon, 11 Feb 2019 17:33:20 +0000
Subject: [PATCH] Fix possible assertion failure in IndicesQueryCache.close
 (#38731)

The assertion that the stats2 map is empty in
IndicesQueryCache.close has been observed to
fail very occasionally in internal cluster tests.

The likely cause is a cross-thread visibility
problem for a count variable.  This change
makes that count volatile.

Relates #37117
Backport of #38714
---
 .../main/java/org/elasticsearch/indices/IndicesQueryCache.java  | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/server/src/main/java/org/elasticsearch/indices/IndicesQueryCache.java b/server/src/main/java/org/elasticsearch/indices/IndicesQueryCache.java
index 1dfbc3af42b..814288dbe58 100644
--- a/server/src/main/java/org/elasticsearch/indices/IndicesQueryCache.java
+++ b/server/src/main/java/org/elasticsearch/indices/IndicesQueryCache.java
@@ -206,7 +206,7 @@ public class IndicesQueryCache implements QueryCache, Closeable {
     }
 
     private static class StatsAndCount {
-        int count;
+        volatile int count;
         final Stats stats;
 
         StatsAndCount(Stats stats) {