use concurrentHashMap explicitly

Signed-off-by: Kiran Prakash <awskiran@amazon.com>

Author: kiranprakash154

CHANGELOG.md

@@ -24,6 +24,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 ### Removed
 
 ### Fixed
+- Used ConcurrentHashMap explicitly in IndicesRequestCache ([#14409](https://github.com/opensearch-project/OpenSearch/pull/14409))
 
 ### Security
 

server/src/main/java/org/opensearch/indices/IndicesRequestCache.java

@@ -81,6 +81,7 @@
 import java.util.Objects;
 import java.util.Optional;
 import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
@@ -506,15 +507,15 @@ public int hashCode() {
      * */
     class IndicesRequestCacheCleanupManager implements Closeable {
         private final Set<CleanupKey> keysToClean;
-        private final ConcurrentMap<ShardId, ConcurrentMap<String, Integer>> cleanupKeyToCountMap;
+        private final ConcurrentHashMap<ShardId, ConcurrentHashMap<String, Integer>> cleanupKeyToCountMap;
         private final AtomicInteger staleKeysCount;
         private volatile double stalenessThreshold;
         private final IndicesRequestCacheCleaner cacheCleaner;
 
         IndicesRequestCacheCleanupManager(ThreadPool threadpool, TimeValue cleanInterval, double stalenessThreshold) {
             this.stalenessThreshold = stalenessThreshold;
             this.keysToClean = ConcurrentCollections.newConcurrentSet();
-            this.cleanupKeyToCountMap = ConcurrentCollections.newConcurrentMap();
+            this.cleanupKeyToCountMap = new ConcurrentHashMap<>();
             this.staleKeysCount = new AtomicInteger(0);
             this.cacheCleaner = new IndicesRequestCacheCleaner(this, threadpool, cleanInterval);
             threadpool.schedule(cacheCleaner, cleanInterval, ThreadPool.Names.SAME);
@@ -572,8 +573,13 @@ private void updateStaleCountOnCacheInsert(CleanupKey cleanupKey) {
 
         // pkg-private for testing
         void addToCleanupKeyToCountMap(ShardId shardId, String readerCacheKeyId) {
-            cleanupKeyToCountMap.computeIfAbsent(shardId, k -> ConcurrentCollections.newConcurrentMap())
-                .merge(readerCacheKeyId, 1, Integer::sum);
+            cleanupKeyToCountMap.compute(shardId, (currentShardId, readerCacheKeyMap) -> {
+                if (readerCacheKeyMap == null) {
+                    readerCacheKeyMap = new ConcurrentHashMap<>();
+                }
+                readerCacheKeyMap.compute(readerCacheKeyId, (currentReaderCacheKeyId, count) -> (count == null) ? 1 : count + 1);
+                return readerCacheKeyMap;
+            });
         }
 
         /**
@@ -831,7 +837,7 @@ public void close() {
         }
 
         // for testing
-        ConcurrentMap<ShardId, ConcurrentMap<String, Integer>> getCleanupKeyToCountMap() {
+        ConcurrentHashMap<ShardId, ConcurrentHashMap<String, Integer>> getCleanupKeyToCountMap() {
             return cleanupKeyToCountMap;
         }
 

server/src/test/java/org/opensearch/indices/IndicesRequestCacheTests.java

@@ -101,7 +101,6 @@
 import java.util.Optional;
 import java.util.UUID;
 import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.ConcurrentMap;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
@@ -491,7 +490,8 @@ public void testStaleCount_OnRemovalNotificationOfStaleKey_DecrementsStaleCount(
             indexShard.hashCode()
         );
         // test the mapping
-        ConcurrentMap<ShardId, ConcurrentMap<String, Integer>> cleanupKeyToCountMap = cache.cacheCleanupManager.getCleanupKeyToCountMap();
+        ConcurrentHashMap<ShardId, ConcurrentHashMap<String, Integer>> cleanupKeyToCountMap = cache.cacheCleanupManager
+            .getCleanupKeyToCountMap();
         // shard id should exist
         assertTrue(cleanupKeyToCountMap.containsKey(shardId));
         // reader CacheKeyId should NOT exist
@@ -554,7 +554,8 @@ public void testStaleCount_OnRemovalNotificationOfNonStaleKey_DoesNotDecrementsS
         );
 
         // test the mapping
-        ConcurrentMap<ShardId, ConcurrentMap<String, Integer>> cleanupKeyToCountMap = cache.cacheCleanupManager.getCleanupKeyToCountMap();
+        ConcurrentHashMap<ShardId, ConcurrentHashMap<String, Integer>> cleanupKeyToCountMap = cache.cacheCleanupManager
+            .getCleanupKeyToCountMap();
         // shard id should exist
         assertTrue(cleanupKeyToCountMap.containsKey(shardId));
         // reader CacheKeyId should NOT exist
@@ -722,7 +723,8 @@ public void testCleanupKeyToCountMapAreSetAppropriately() throws Exception {
         cache.getOrCompute(getEntity(indexShard), getLoader(reader), reader, getTermBytes());
         assertEquals(1, cache.count());
         // test the mappings
-        ConcurrentMap<ShardId, ConcurrentMap<String, Integer>> cleanupKeyToCountMap = cache.cacheCleanupManager.getCleanupKeyToCountMap();
+        ConcurrentHashMap<ShardId, ConcurrentHashMap<String, Integer>> cleanupKeyToCountMap = cache.cacheCleanupManager
+            .getCleanupKeyToCountMap();
         assertEquals(1, (int) cleanupKeyToCountMap.get(shardId).get(getReaderCacheKeyId(reader)));
 
         cache.getOrCompute(getEntity(indexShard), getLoader(secondReader), secondReader, getTermBytes());