Fix cache expire after access

This commit fixes a bug in the cache expire after access
implementation. The bug is this: if you construct a cache with an expire
after access of T, put a key, and then touch the key at some time t > T,
the act of getting the key would update the access time for the entry
before checking if the entry was expired. There are situations in which
expire after access would be honored (e.g., if the cache needs to prune
the LRU list to keep the cache under a certain weight, or a manual
refresh was called) but this behavior is otherwise broken.

Relates #24546

1 files changed, 22 insertions, 0 deletions

diff --git a/core/src/test/java/org/elasticsearch/common/cache/CacheTests.java b/core/src/test/java/org/elasticsearch/common/cache/CacheTests.java
index 71fe7b262a..7dbaba0289 100644
--- a/core/src/test/java/org/elasticsearch/common/cache/CacheTests.java
+++ b/core/src/test/java/org/elasticsearch/common/cache/CacheTests.java
@@ -257,6 +257,28 @@ public class CacheTests extends ESTestCase {
         }
     }
 
+    public void testSimpleExpireAfterAccess() {
+        AtomicLong now = new AtomicLong();
+        Cache<Integer, String> cache = new Cache<Integer, String>() {
+            @Override
+            protected long now() {
+                return now.get();
+            }
+        };
+        cache.setExpireAfterAccessNanos(1);
+        now.set(0);
+        for (int i = 0; i < numberOfEntries; i++) {
+            cache.put(i, Integer.toString(i));
+        }
+        for (int i = 0; i < numberOfEntries; i++) {
+            assertEquals(cache.get(i), Integer.toString(i));
+        }
+        now.set(2);
+        for(int i = 0; i < numberOfEntries; i++) {
+            assertNull(cache.get(i));
+        }
+    }
+
     public void testExpirationAfterWrite() {
         AtomicLong now = new AtomicLong();
         Cache<Integer, String> cache = new Cache<Integer, String>() {