Added server distribution and version into response header

Signed-off-by: Sam Hobbs <[email protected]>

CHANGELOG.md

@@ -10,7 +10,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Allow mmap to use new JDK-19 preview APIs in Apache Lucene 9.4+ ([#5151](https://github.com/opensearch-project/OpenSearch/pull/5151))
 - Add events correlation engine plugin ([#6854](https://github.com/opensearch-project/OpenSearch/issues/6854))
 - Add support for ignoring missing Javadoc on generated code using annotation ([#7604](https://github.com/opensearch-project/OpenSearch/pull/7604))
-
+- Added server version as response header [#6583](https://github.com/opensearch-project/OpenSearch/issues/6583)
 ### Dependencies
 - Bump `log4j-core` from 2.18.0 to 2.19.0
 - Bump `forbiddenapis` from 3.3 to 3.4
@@ -154,4 +154,4 @@ 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/2.7...2.x
+[Unreleased 2.x]: https://github.com/opensearch-project/OpenSearch/compare/2.7...2.x

server/src/main/java/org/opensearch/http/DefaultRestChannel.java

@@ -32,6 +32,7 @@
 
 package org.opensearch.http;
 
+import org.opensearch.Build;
 import org.opensearch.action.ActionListener;
 import org.opensearch.common.Nullable;
 import org.opensearch.common.bytes.BytesArray;
@@ -50,6 +51,7 @@
 import org.opensearch.rest.RestStatus;
 
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
@@ -77,6 +79,7 @@ public class DefaultRestChannel extends AbstractRestChannel implements RestChann
     private final HttpChannel httpChannel;
     private final CorsHandler corsHandler;
 
+
     @Nullable
     private final HttpTracer tracerLog;
 
@@ -147,12 +150,25 @@ public void sendResponse(RestResponse restResponse) {
             addCustomHeaders(httpResponse, restResponse.getHeaders());
             addCustomHeaders(httpResponse, threadContext.getResponseHeaders());
 
+            Map<String, List<String>> serverHeader = new HashMap<>();
+            List<String> serverHeaderString = new ArrayList<>();
+
+            serverHeaderString.add("OpenSearch/" + Build.CURRENT.getQualifiedVersion() + " (" +   Build.CURRENT.getDistribution() + ")");
+
+            serverHeader.put("serverHeader", serverHeaderString);
+
+            addCustomHeaders(httpResponse,  serverHeader);
+
             // If our response doesn't specify a content-type header, set one
             setHeaderField(httpResponse, CONTENT_TYPE, restResponse.contentType(), false);
             // If our response has no content-length, calculate and set one
             contentLength = String.valueOf(restResponse.content().length());
             setHeaderField(httpResponse, CONTENT_LENGTH, contentLength, false);
 
+
+
+
+
             addCookies(httpResponse);
 
             BytesStreamOutput bytesStreamOutput = bytesOutputOrNull();