Added the addition of the server version and distribution as a respon…

CHANGELOG.md

@@ -105,6 +105,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Create concept of persistent ThreadContext headers that are unstashable ([#8291]()https://github.com/opensearch-project/OpenSearch/pull/8291)
 - [Search pipelines] Add Global Ignore_failure options for Processors ([#8373](https://github.com/opensearch-project/OpenSearch/pull/8373))
 - Enable Partial Flat Object ([#7997](https://github.com/opensearch-project/OpenSearch/pull/7997))
+- Add server version as REST response header [#6583](https://github.com/opensearch-project/OpenSearch/issues/6583)
 - Add jdk.incubator.vector module support for JDK 20+ ([#8601](https://github.com/opensearch-project/OpenSearch/pull/8601))
 - Introduce full support for Search Pipeline ([#8613](https://github.com/opensearch-project/OpenSearch/pull/8613))
 

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.core.common.bytes.BytesArray;
@@ -48,7 +49,6 @@
 import org.opensearch.rest.RestRequest;
 import org.opensearch.rest.RestResponse;
 import org.opensearch.core.rest.RestStatus;
-
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
@@ -69,13 +69,20 @@ public class DefaultRestChannel extends AbstractRestChannel implements RestChann
     static final String CONTENT_TYPE = "content-type";
     static final String CONTENT_LENGTH = "content-length";
     static final String SET_COOKIE = "set-cookie";
+    static final String SERVER_VERSION = "X-OpenSearch-Version";
+    static final String SERVER_VERSION_VALUE = "OpenSearch/"
+        + Build.CURRENT.getQualifiedVersion()
+        + " ("
+        + Build.CURRENT.getDistribution()
+        + ")";
 
     private final HttpRequest httpRequest;
     private final BigArrays bigArrays;
     private final HttpHandlingSettings settings;
     private final ThreadContext threadContext;
     private final HttpChannel httpChannel;
     private final CorsHandler corsHandler;
+    private final Map<String, List<String>> SERVER_VERSION_HEADER = Map.of(SERVER_VERSION, List.of(SERVER_VERSION_VALUE));
 
     @Nullable
     private final HttpTracer tracerLog;
@@ -147,6 +154,8 @@ public void sendResponse(RestResponse restResponse) {
             addCustomHeaders(httpResponse, restResponse.getHeaders());
             addCustomHeaders(httpResponse, threadContext.getResponseHeaders());
 
+            addCustomHeaders(httpResponse, SERVER_VERSION_HEADER);
+
             // 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

server/src/test/java/org/opensearch/http/DefaultRestChannelTests.java

@@ -32,6 +32,7 @@
 
 package org.opensearch.http;
 
+import org.opensearch.Build;
 import org.opensearch.action.ActionListener;
 import org.opensearch.core.common.bytes.BytesArray;
 import org.opensearch.core.common.bytes.BytesReference;
@@ -189,6 +190,10 @@ public void testHeadersSet() {
         assertEquals("abc", headers.get(Task.X_OPAQUE_ID).get(0));
         assertEquals(Integer.toString(resp.content().length()), headers.get(DefaultRestChannel.CONTENT_LENGTH).get(0));
         assertEquals(resp.contentType(), headers.get(DefaultRestChannel.CONTENT_TYPE).get(0));
+        assertEquals(
+            "OpenSearch/" + Build.CURRENT.getQualifiedVersion() + " (" + Build.CURRENT.getDistribution() + ")",
+            headers.get("X-OpenSearch-Version").get(0)
+        );
     }
 
     public void testCookiesSet() {