From 2e445d3ede953c90e4e1ce69e5f53192115b9dd7 Mon Sep 17 00:00:00 2001
From: Jason Tedor <jason@tedor.me>
Date: Tue, 13 Oct 2015 22:14:13 -0400
Subject: [PATCH] Do not pollute Cache with failed futures

---
 .../java/org/elasticsearch/common/cache/Cache.java | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/core/src/main/java/org/elasticsearch/common/cache/Cache.java b/core/src/main/java/org/elasticsearch/common/cache/Cache.java
index f16e7d8d25d..a686ecc9645 100644
--- a/core/src/main/java/org/elasticsearch/common/cache/Cache.java
+++ b/core/src/main/java/org/elasticsearch/common/cache/Cache.java
@@ -340,8 +340,18 @@ public class Cache<K, V> {
             Entry<K, V> entry;
             try {
                 entry = future.get();
-            } catch (InterruptedException e) {
-                throw new ExecutionException(e);
+            } catch (ExecutionException | InterruptedException e) {
+                // if the future ended exceptionally, we do not want to pollute the cache
+                // however, we have to take care to ensure that the polluted entry has not already been replaced
+                try (ReleasableLock ignored = segment.writeLock.acquire()) {
+                    Future<Entry<K, V>> sanity = segment.map.get(key);
+                    try {
+                        sanity.get();
+                    } catch (ExecutionException | InterruptedException gotcha) {
+                        segment.map.remove(key);
+                    }
+                }
+                throw (e instanceof ExecutionException) ? (ExecutionException)e : new ExecutionException(e);
             }
             if (entry.value == null) {
                 throw new ExecutionException(new NullPointerException("loader returned a null value"));