[Backport 2.x][Tiered Caching] Enable serialization of IndicesRequestCache.Key (#10…

CHANGELOG.md

@@ -18,6 +18,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Add search query categorizor ([#10255](https://github.com/opensearch-project/OpenSearch/pull/10255))
 - Per request phase latency ([#10351](https://github.com/opensearch-project/OpenSearch/issues/10351))
 - Add cluster state stats ([#10670](https://github.com/opensearch-project/OpenSearch/pull/10670))
+- [Tiered caching] Enabling serialization for IndicesRequestCache key object ([#10275](https://github.com/opensearch-project/OpenSearch/pull/10275))
 - [Tiered caching] Defining interfaces, listeners and extending IndicesRequestCache with Tiered cache support ([#10753](https://github.com/opensearch-project/OpenSearch/pull/10753))
 - Remove ingest processor supports excluding fields ([#10967](https://github.com/opensearch-project/OpenSearch/pull/10967), [#11983](https://github.com/opensearch-project/OpenSearch/pull/11983))
 - [Remote cluster state] Restore cluster state version during remote state auto restore ([#10853](https://github.com/opensearch-project/OpenSearch/pull/10853))

libs/core/src/main/java/org/opensearch/core/index/shard/ShardId.java

@@ -32,6 +32,7 @@
 
 package org.opensearch.core.index.shard;
 
+import org.apache.lucene.util.RamUsageEstimator;
 import org.opensearch.common.annotation.PublicApi;
 import org.opensearch.core.common.Strings;
 import org.opensearch.core.common.io.stream.StreamInput;
@@ -55,6 +56,8 @@ public class ShardId implements Comparable<ShardId>, ToXContentFragment, Writeab
     private final int shardId;
     private final int hashCode;
 
+    private final static long BASE_RAM_BYTES_USED = RamUsageEstimator.shallowSizeOfInstance(ShardId.class);
+
     /**
      * Constructs a new shard id.
      * @param index the index name
@@ -88,6 +91,10 @@ public ShardId(StreamInput in) throws IOException {
         hashCode = computeHashCode();
     }
 
+    public long getBaseRamBytesUsed() {
+        return BASE_RAM_BYTES_USED;
+    }
+
     /**
      * Writes this shard id to a stream.
      * @param out the stream to write to

server/src/internalClusterTest/java/org/opensearch/indices/IndicesRequestCacheIT.java

@@ -630,6 +630,45 @@ public void testProfileDisableCache() throws Exception {
         }
     }
 
+    public void testCacheWithInvalidation() throws Exception {
+        Client client = client();
+        assertAcked(
+            client.admin()
+                .indices()
+                .prepareCreate("index")
+                .setMapping("k", "type=keyword")
+                .setSettings(
+                    Settings.builder()
+                        .put(IndicesRequestCache.INDEX_CACHE_REQUEST_ENABLED_SETTING.getKey(), true)
+                        .put(IndexMetadata.SETTING_NUMBER_OF_SHARDS, 1)
+                        .put(IndexMetadata.SETTING_NUMBER_OF_REPLICAS, 0)
+                )
+                .get()
+        );
+        indexRandom(true, client.prepareIndex("index").setSource("k", "hello"));
+        ensureSearchable("index");
+        SearchResponse resp = client.prepareSearch("index").setRequestCache(true).setQuery(QueryBuilders.termQuery("k", "hello")).get();
+        assertSearchResponse(resp);
+        OpenSearchAssertions.assertAllSuccessful(resp);
+        assertThat(resp.getHits().getTotalHits().value, equalTo(1L));
+
+        assertCacheState(client, "index", 0, 1);
+        // Index but don't refresh
+        indexRandom(false, client.prepareIndex("index").setSource("k", "hello2"));
+        resp = client.prepareSearch("index").setRequestCache(true).setQuery(QueryBuilders.termQuery("k", "hello")).get();
+        assertSearchResponse(resp);
+        // Should expect hit as here as refresh didn't happen
+        assertCacheState(client, "index", 1, 1);
+
+        // Explicit refresh would invalidate cache
+        refresh();
+        // Hit same query again
+        resp = client.prepareSearch("index").setRequestCache(true).setQuery(QueryBuilders.termQuery("k", "hello")).get();
+        assertSearchResponse(resp);
+        // Should expect miss as key has changed due to change in IndexReader.CacheKey (due to refresh)
+        assertCacheState(client, "index", 1, 2);
+    }
+
     private static void assertCacheState(Client client, String index, long expectedHits, long expectedMisses) {
         RequestCacheStats requestCacheStats = client.admin()
             .indices()
@@ -644,6 +683,7 @@ private static void assertCacheState(Client client, String index, long expectedH
             Arrays.asList(expectedHits, expectedMisses, 0L),
             Arrays.asList(requestCacheStats.getHitCount(), requestCacheStats.getMissCount(), requestCacheStats.getEvictions())
         );
+
     }
 
 }

server/src/main/java/org/opensearch/common/lucene/index/OpenSearchDirectoryReader.java

@@ -40,6 +40,8 @@
 import org.opensearch.core.index.shard.ShardId;
 
 import java.io.IOException;
+import java.util.Optional;
+import java.util.UUID;
 
 /**
  * A {@link org.apache.lucene.index.FilterDirectoryReader} that exposes
@@ -53,11 +55,14 @@ public final class OpenSearchDirectoryReader extends FilterDirectoryReader {
     private final ShardId shardId;
     private final FilterDirectoryReader.SubReaderWrapper wrapper;
 
+    private final DelegatingCacheHelper delegatingCacheHelper;
+
     private OpenSearchDirectoryReader(DirectoryReader in, FilterDirectoryReader.SubReaderWrapper wrapper, ShardId shardId)
         throws IOException {
         super(in, wrapper);
         this.wrapper = wrapper;
         this.shardId = shardId;
+        this.delegatingCacheHelper = new DelegatingCacheHelper(in.getReaderCacheHelper());
     }
 
     /**
@@ -70,7 +75,61 @@ public ShardId shardId() {
     @Override
     public CacheHelper getReaderCacheHelper() {
         // safe to delegate since this reader does not alter the index
-        return in.getReaderCacheHelper();
+        return this.delegatingCacheHelper;
+    }
+
+    public DelegatingCacheHelper getDelegatingCacheHelper() {
+        return this.delegatingCacheHelper;
+    }
+
+    /**
+     * Wraps existing IndexReader cache helper which internally provides a way to wrap CacheKey.
+     * @opensearch.internal
+     */
+    public class DelegatingCacheHelper implements CacheHelper {
+        private final CacheHelper cacheHelper;
+        private final DelegatingCacheKey serializableCacheKey;
+
+        DelegatingCacheHelper(CacheHelper cacheHelper) {
+            this.cacheHelper = cacheHelper;
+            this.serializableCacheKey = new DelegatingCacheKey(Optional.ofNullable(cacheHelper).map(key -> getKey()).orElse(null));
+        }
+
+        @Override
+        public CacheKey getKey() {
+            return this.cacheHelper.getKey();
+        }
+
+        public DelegatingCacheKey getDelegatingCacheKey() {
+            return this.serializableCacheKey;
+        }
+
+        @Override
+        public void addClosedListener(ClosedListener listener) {
+            this.cacheHelper.addClosedListener(listener);
+        }
+    }
+
+    /**
+     *  Wraps internal IndexReader.CacheKey and attaches a uniqueId to it which can be eventually be used instead of
+     *  object itself for serialization purposes.
+     */
+    public class DelegatingCacheKey {
+        private final CacheKey cacheKey;
+        private final String uniqueId;
+
+        DelegatingCacheKey(CacheKey cacheKey) {
+            this.cacheKey = cacheKey;
+            this.uniqueId = UUID.randomUUID().toString();
+        }
+
+        public CacheKey getCacheKey() {
+            return this.cacheKey;
+        }
+
+        public String getId() {
+            return uniqueId;
+        }
     }
 
     @Override