Fix possible assertion failure in IndicesQueryCache.close (#38733)

droberts195 · web-flow · commit 3b1abd7a706b · 2019-02-11T17:33:52.000Z
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
diff --git a/server/src/main/java/org/elasticsearch/indices/IndicesQueryCache.java b/server/src/main/java/org/elasticsearch/indices/IndicesQueryCache.java
@@ -206,7 +206,7 @@ QueryCacheStats toQueryCacheStats() {
     }
 
     private static class StatsAndCount {
-        int count;
+        volatile int count;
         final Stats stats;
 
         StatsAndCount(Stats stats) {

Original file line number	Diff line number	Diff line change
`@@ -206,7 +206,7 @@ QueryCacheStats toQueryCacheStats() {`
`206`	`206`	`}`
`207`	`207`
`208`	`208`	`private static class StatsAndCount {`
`209`		`- int count;`
	`209`	`+ volatile int count;`
`210`	`210`	`final Stats stats;`
`211`	`211`
`212`	`212`	`StatsAndCount(Stats stats) {`