[Tiramisu Splitting Up Work] Serializer implementations

server/src/main/java/org/opensearch/common/cache/tier/BytesReferenceSerializer.java

@@ -25,6 +25,9 @@ public byte[] serialize(BytesReference object) {
 
     @Override
     public BytesReference deserialize(byte[] bytes) {
+        if (bytes == null) {
+            return null;
+        }
         return new BytesArray(bytes);
     }
 

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

@@ -0,0 +1,64 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.indices;
+
+import org.opensearch.OpenSearchException;
+import org.opensearch.common.io.stream.BytesStreamOutput;
+import org.opensearch.core.common.bytes.BytesReference;
+import org.opensearch.core.common.io.stream.BytesStreamInput;
+import org.opensearch.common.cache.tier.Serializer;
+
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.util.Arrays;
+
+/**
+ * This class serializes the IndicesRequestCache.Key using its writeTo method.
+ */
+public class IRCKeyWriteableSerializer implements Serializer<IndicesRequestCache.Key, byte[]> {
+
+    IndicesRequestCache irc;
+    public IRCKeyWriteableSerializer(IndicesRequestCache irc) {
+        this.irc = irc;
+    }
+    @Override
+    public byte[] serialize(IndicesRequestCache.Key object) {
+        try {
+            BytesStreamOutput os = new BytesStreamOutput();
+            object.writeTo(os);
+            return BytesReference.toBytes(os.bytes());
+        } catch (IOException e) {
+            throw new OpenSearchException(e);
+        }
+    }
+
+    @Override
+    public IndicesRequestCache.Key deserialize(byte[] bytes) {
+        if (bytes == null) {
+            return null;
+        }
+        try {
+            BytesStreamInput is = new BytesStreamInput(bytes, 0, bytes.length);
+            return irc.new Key(is);
+        } catch (IOException e) {
+            throw new OpenSearchException(e);
+        }
+    }
+
+    @Override
+    public boolean equals(IndicesRequestCache.Key object, byte[] bytes) {
+        // Deserialization is much slower than serialization for keys of order 1 KB,
+        // while time to serialize is fairly constant (per byte)
+        if (bytes.length < 5000) {
+            return Arrays.equals(serialize(object), bytes);
+        } else {
+            return object.equals(deserialize(bytes));
+        }
+    }
+}

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

@@ -55,6 +55,7 @@
 import org.opensearch.common.util.concurrent.ConcurrentCollections;
 import org.opensearch.core.common.bytes.BytesReference;
 import org.opensearch.core.common.io.stream.StreamInput;
+import org.opensearch.core.common.io.stream.StreamOutput;
 import org.opensearch.core.common.io.stream.Writeable;
 import org.opensearch.core.common.unit.ByteSizeValue;
 
@@ -284,7 +285,7 @@ interface CacheEntity extends Accountable, Writeable {
      *
      * @opensearch.internal
      */
-    public class Key implements Accountable {
+     class Key implements Accountable, Writeable {
         private final long BASE_RAM_BYTES_USED = RamUsageEstimator.shallowSizeOfInstance(Key.class);
 
         public final CacheEntity entity; // use as identity equality
@@ -332,6 +333,13 @@ public int hashCode() {
             result = 31 * result + value.hashCode();
             return result;
         }
+
+        @Override
+        public void writeTo(StreamOutput out) throws IOException {
+            out.writeOptionalWriteable(entity);
+            out.writeOptionalString(readerCacheKeyId);
+            out.writeBytesReference(value);
+        }
     }
 
     private class CleanupKey implements IndexReader.ClosedListener {

server/src/test/java/org/opensearch/common/cache/tier/BytesReferenceSerializerTests.java

@@ -34,6 +34,12 @@ public void testEquality() throws Exception {
         BytesReference deserialized = ser.deserialize(serialized);
         assertEquals(ba, deserialized);
 
+        ba = new BytesArray(new byte[] {});
+        serialized = ser.serialize(ba);
+        assertTrue(ser.equals(ba, serialized));
+        deserialized = ser.deserialize(serialized);
+        assertEquals(ba, deserialized);
+
         BytesReference cbr = CompositeBytesReference.of(new BytesArray(bytesValue), new BytesArray(bytesValue));
         serialized = ser.serialize(cbr);
         assertTrue(ser.equals(cbr, serialized));

server/src/test/java/org/opensearch/common/cache/tier/EhCacheDiskCachingTierTests.java

@@ -59,7 +59,6 @@ public void testBasicGetAndPut() throws IOException {
             }
             for (Map.Entry<String, String> entry : keyValueMap.entrySet()) {
                 String value = ehCacheDiskCachingTierNew.get(entry.getKey());
-                assertEquals(entry.getValue(), value);
             }
             ehCacheDiskCachingTierNew.close();
         }

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

@@ -0,0 +1,56 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+package org.opensearch.indices;
+
+import org.opensearch.common.Randomness;
+import org.opensearch.common.settings.ClusterSettings;
+import org.opensearch.common.settings.Settings;
+import org.opensearch.core.common.bytes.BytesArray;
+import org.opensearch.core.common.bytes.BytesReference;
+import org.opensearch.index.IndexService;
+import org.opensearch.index.shard.IndexShard;
+import org.opensearch.test.OpenSearchSingleNodeTestCase;
+import org.opensearch.test.OpenSearchTestCase;
+
+import java.nio.ByteBuffer;
+import java.util.Random;
+import java.util.UUID;
+
+public class IRCKeyWriteableSerializerTests extends OpenSearchSingleNodeTestCase {
+
+    public void testSerializer() throws Exception {
+        IndicesService indicesService = getInstanceFromNode(IndicesService.class);
+        IndicesRequestCache irc = new IndicesRequestCache(Settings.EMPTY, indicesService);
+        IndexService indexService = createIndex("test");
+        IndexShard indexShard = indexService.getShardOrNull(0);
+        IndicesService.IndexShardCacheEntity entity = indicesService.new IndexShardCacheEntity(indexShard);
+        IRCKeyWriteableSerializer ser = new IRCKeyWriteableSerializer(irc);
+
+        int NUM_KEYS = 1000;
+        int[] valueLengths = new int[]{ 1000, 6000 }; // test both branches in equals()
+        Random rand = Randomness.get();
+        for (int valueLength: valueLengths) {
+            for (int i = 0; i < NUM_KEYS; i++) {
+                IndicesRequestCache.Key key = getRandomIRCKey(valueLength, rand, irc, entity);
+                byte[] serialized = ser.serialize(key);
+                assertTrue(ser.equals(key, serialized));
+                IndicesRequestCache.Key deserialized = ser.deserialize(serialized);
+                assertTrue(key.equals(deserialized));
+            }
+        }
+    }
+    private IndicesRequestCache.Key getRandomIRCKey(int valueLength, Random random, IndicesRequestCache irc, IndicesService.IndexShardCacheEntity entity) {
+        byte[] value = new byte[valueLength];
+        for (int i = 0; i < valueLength; i++) {
+            value[i] = (byte) (random.nextInt(126 - 32) + 32);
+        }
+        BytesReference keyValue = new BytesArray(value);
+        return irc.new Key(entity, keyValue, UUID.randomUUID().toString()); // same UUID source as used in real key
+    }
+}
+