Add changelog and license

Signed-off-by: Aman Khare <[email protected]>

CHANGELOG.md

@@ -53,6 +53,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Change http code on create index API with bad input raising NotXContentException from 500 to 400 ([#4773](https://github.com/opensearch-project/OpenSearch/pull/4773))
 - Change http code for DecommissioningFailedException from 500 to 400 ([#5283](https://github.com/opensearch-project/OpenSearch/pull/5283))
 - Improve summary error message for invalid setting updates ([#4792](https://github.com/opensearch-project/OpenSearch/pull/4792))
+- Compress and cache cluster state during validate join request ([#7321](https://github.com/opensearch-project/OpenSearch/pull/7321))
 
 ### Deprecated
 
@@ -99,4 +100,4 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 ### Security
 
 [Unreleased 3.0]: https://github.com/opensearch-project/OpenSearch/compare/2.x...HEAD
-[Unreleased 2.x]: https://github.com/opensearch-project/OpenSearch/compare/2.5...2.x
+[Unreleased 2.x]: https://github.com/opensearch-project/OpenSearch/compare/2.5...2.x

server/src/main/java/org/opensearch/cluster/CompressionHelper.java

@@ -1,3 +1,11 @@
+/*
+ * 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.cluster;
 
 import org.apache.logging.log4j.LogManager;
@@ -18,6 +26,15 @@
 public class CompressionHelper {
     private static final Logger logger = LogManager.getLogger(CompressionHelper.class);
 
+    /**
+     * It'll always use compression before writing on a newly created output stream.
+     * @param writer Object which is going to write the content
+     * @param nodeVersion version of cluster node
+     * @param streamBooleanFlag flag used at receiver end to make intelligent decisions. For example, ClusterState
+     *                          assumes full state of diff of the states based on this flag.
+     * @return reference to serialized bytes
+     * @throws IOException
+     */
     public static BytesReference serializedWrite(Writeable writer, Version nodeVersion, boolean streamBooleanFlag) throws IOException {
         final BytesStreamOutput bStream = new BytesStreamOutput();
         try (StreamOutput stream = new OutputStreamStreamOutput(CompressorFactory.COMPRESSOR.threadLocalOutputStream(bStream))) {