[Backport 2.0] Revert "[Remove] MainResponse version override cluster setting (#3031) (#3032)"

client/rest-high-level/src/test/java/org/opensearch/client/PingAndInfoIT.java

@@ -33,6 +33,7 @@
 package org.opensearch.client;
 
 import org.apache.http.client.methods.HttpGet;
+import org.opensearch.action.main.TransportMainAction;
 import org.opensearch.client.core.MainResponse;
 
 import java.io.IOException;
@@ -62,4 +63,25 @@ public void testInfo() throws IOException {
         assertTrue(versionMap.get("number").toString().startsWith(info.getVersion().getNumber()));
         assertEquals(versionMap.get("lucene_version"), info.getVersion().getLuceneVersion());
     }
+
+    public void testInfo_overrideResponseVersion() throws IOException {
+        Request overrideResponseVersionRequest = new Request("PUT", "/_cluster/settings");
+        overrideResponseVersionRequest.setOptions(expectWarnings(TransportMainAction.OVERRIDE_MAIN_RESPONSE_VERSION_DEPRECATION_MESSAGE));
+        overrideResponseVersionRequest.setJsonEntity("{\"persistent\":{\"compatibility\": {\"override_main_response_version\":true}}}");
+        client().performRequest(overrideResponseVersionRequest);
+
+        MainResponse info = highLevelClient().info(RequestOptions.DEFAULT);
+        assertEquals("7.10.2", info.getVersion().getNumber());
+
+        // Set back to default version.
+        Request resetResponseVersionRequest = new Request("PUT", "/_cluster/settings");
+        resetResponseVersionRequest.setJsonEntity("{\"persistent\":{\"compatibility\": {\"override_main_response_version\":null}}}");
+        client().performRequest(resetResponseVersionRequest);
+
+        Map<String, Object> infoAsMap = entityAsMap(adminClient().performRequest(new Request(HttpGet.METHOD_NAME, "/")));
+        @SuppressWarnings("unchecked")
+        Map<String, Object> versionMap = (Map<String, Object>) infoAsMap.get("version");
+        info = highLevelClient().info(RequestOptions.DEFAULT);
+        assertTrue(versionMap.get("number").toString().startsWith(info.getVersion().getNumber()));
+    }
 }

server/src/main/java/org/opensearch/action/main/MainResponse.java

@@ -60,6 +60,7 @@ public class MainResponse extends ActionResponse implements ToXContentObject {
     private ClusterName clusterName;
     private String clusterUuid;
     private Build build;
+    private String versionNumber;
     public static final String TAGLINE = "The OpenSearch Project: https://opensearch.org/";
 
     MainResponse() {}
@@ -74,6 +75,7 @@ public class MainResponse extends ActionResponse implements ToXContentObject {
         if (in.getVersion().before(LegacyESVersion.V_7_0_0)) {
             in.readBoolean();
         }
+        versionNumber = build.getQualifiedVersion();
     }
 
     public MainResponse(String nodeName, Version version, ClusterName clusterName, String clusterUuid, Build build) {
@@ -82,6 +84,16 @@ public MainResponse(String nodeName, Version version, ClusterName clusterName, S
         this.clusterName = clusterName;
         this.clusterUuid = clusterUuid;
         this.build = build;
+        this.versionNumber = build.getQualifiedVersion();
+    }
+
+    public MainResponse(String nodeName, Version version, ClusterName clusterName, String clusterUuid, Build build, String versionNumber) {
+        this.nodeName = nodeName;
+        this.version = version;
+        this.clusterName = clusterName;
+        this.clusterUuid = clusterUuid;
+        this.build = build;
+        this.versionNumber = versionNumber;
     }
 
     public String getNodeName() {
@@ -104,10 +116,18 @@ public Build getBuild() {
         return build;
     }
 
+    public String getVersionNumber() {
+        return versionNumber;
+    }
+
     @Override
     public void writeTo(StreamOutput out) throws IOException {
         out.writeString(nodeName);
-        Version.writeVersion(version, out);
+        if (out.getVersion().before(Version.V_1_0_0)) {
+            Version.writeVersion(LegacyESVersion.V_7_10_2, out);
+        } else {
+            Version.writeVersion(version, out);
+        }
         clusterName.writeTo(out);
         out.writeString(clusterUuid);
         Build.writeBuild(build, out);
@@ -122,9 +142,11 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
         builder.field("name", nodeName);
         builder.field("cluster_name", clusterName.value());
         builder.field("cluster_uuid", clusterUuid);
-        builder.startObject("version")
-            .field("distribution", build.getDistribution())
-            .field("number", build.getQualifiedVersion())
+        builder.startObject("version");
+        if (isCompatibilityModeDisabled()) {
+            builder.field("distribution", build.getDistribution());
+        }
+        builder.field("number", versionNumber)
             .field("build_type", build.type().displayName())
             .field("build_hash", build.hash())
             .field("build_date", build.date())
@@ -138,6 +160,12 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
         return builder;
     }
 
+    private boolean isCompatibilityModeDisabled() {
+        // if we are not in compatibility mode (spoofing versionNumber), then
+        // build.getQualifiedVersion is always used.
+        return build.getQualifiedVersion().equals(versionNumber);
+    }
+
     private static final ObjectParser<MainResponse, Void> PARSER = new ObjectParser<>(
         MainResponse.class.getName(),
         true,
@@ -166,6 +194,7 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
             response.version = Version.fromString(
                 ((String) value.get("number")).replace("-SNAPSHOT", "").replaceFirst("-(alpha\\d+|beta\\d+|rc\\d+)", "")
             );
+            response.versionNumber = response.version.toString();
         }, (parser, context) -> parser.map(), new ParseField("version"));
     }
 

server/src/main/java/org/opensearch/action/main/TransportMainAction.java

@@ -33,13 +33,16 @@
 package org.opensearch.action.main;
 
 import org.opensearch.Build;
+import org.opensearch.LegacyESVersion;
 import org.opensearch.Version;
 import org.opensearch.action.ActionListener;
 import org.opensearch.action.support.ActionFilters;
 import org.opensearch.action.support.HandledTransportAction;
 import org.opensearch.cluster.ClusterState;
 import org.opensearch.cluster.service.ClusterService;
 import org.opensearch.common.inject.Inject;
+import org.opensearch.common.logging.DeprecationLogger;
+import org.opensearch.common.settings.Setting;
 import org.opensearch.common.settings.Settings;
 import org.opensearch.node.Node;
 import org.opensearch.tasks.Task;
@@ -52,8 +55,23 @@
  */
 public class TransportMainAction extends HandledTransportAction<MainRequest, MainResponse> {
 
+    private static final DeprecationLogger DEPRECATION_LOGGER = DeprecationLogger.getLogger(TransportMainAction.class);
+
+    public static final String OVERRIDE_MAIN_RESPONSE_VERSION_KEY = "compatibility.override_main_response_version";
+
+    public static final Setting<Boolean> OVERRIDE_MAIN_RESPONSE_VERSION = Setting.boolSetting(
+        OVERRIDE_MAIN_RESPONSE_VERSION_KEY,
+        false,
+        Setting.Property.NodeScope,
+        Setting.Property.Dynamic
+    );
+
+    public static final String OVERRIDE_MAIN_RESPONSE_VERSION_DEPRECATION_MESSAGE = "overriding main response version"
+        + " number will be removed in a future version";
+
     private final String nodeName;
     private final ClusterService clusterService;
+    private volatile String responseVersion;
 
     @Inject
     public TransportMainAction(
@@ -65,13 +83,32 @@ public TransportMainAction(
         super(MainAction.NAME, transportService, actionFilters, MainRequest::new);
         this.nodeName = Node.NODE_NAME_SETTING.get(settings);
         this.clusterService = clusterService;
+        setResponseVersion(OVERRIDE_MAIN_RESPONSE_VERSION.get(settings));
+
+        clusterService.getClusterSettings().addSettingsUpdateConsumer(OVERRIDE_MAIN_RESPONSE_VERSION, this::setResponseVersion);
+    }
+
+    private void setResponseVersion(boolean isResponseVersionOverrideEnabled) {
+        if (isResponseVersionOverrideEnabled) {
+            DEPRECATION_LOGGER.deprecate(OVERRIDE_MAIN_RESPONSE_VERSION.getKey(), OVERRIDE_MAIN_RESPONSE_VERSION_DEPRECATION_MESSAGE);
+            this.responseVersion = LegacyESVersion.V_7_10_2.toString();
+        } else {
+            this.responseVersion = Build.CURRENT.getQualifiedVersion();
+        }
     }
 
     @Override
     protected void doExecute(Task task, MainRequest request, ActionListener<MainResponse> listener) {
         ClusterState clusterState = clusterService.state();
         listener.onResponse(
-            new MainResponse(nodeName, Version.CURRENT, clusterState.getClusterName(), clusterState.metadata().clusterUUID(), Build.CURRENT)
+            new MainResponse(
+                nodeName,
+                Version.CURRENT,
+                clusterState.getClusterName(),
+                clusterState.metadata().clusterUUID(),
+                Build.CURRENT,
+                responseVersion
+            )
         );
     }
 }

server/src/main/java/org/opensearch/common/settings/ClusterSettings.java

@@ -32,6 +32,7 @@
 package org.opensearch.common.settings;
 
 import org.apache.logging.log4j.LogManager;
+import org.opensearch.action.main.TransportMainAction;
 import org.opensearch.cluster.routing.allocation.decider.NodeLoadAwareAllocationDecider;
 import org.opensearch.index.IndexModule;
 import org.opensearch.index.IndexSettings;
@@ -553,6 +554,7 @@ public void apply(Settings value, Settings current, Settings previous) {
                 FsHealthService.REFRESH_INTERVAL_SETTING,
                 FsHealthService.SLOW_PATH_LOGGING_THRESHOLD_SETTING,
                 FsHealthService.HEALTHY_TIMEOUT_SETTING,
+                TransportMainAction.OVERRIDE_MAIN_RESPONSE_VERSION,
                 NodeLoadAwareAllocationDecider.CLUSTER_ROUTING_ALLOCATION_LOAD_AWARENESS_PROVISIONED_CAPACITY_SETTING,
                 NodeLoadAwareAllocationDecider.CLUSTER_ROUTING_ALLOCATION_LOAD_AWARENESS_SKEW_FACTOR_SETTING,
                 NodeLoadAwareAllocationDecider.CLUSTER_ROUTING_ALLOCATION_LOAD_AWARENESS_ALLOW_UNASSIGNED_PRIMARIES_SETTING,

server/src/test/java/org/opensearch/action/main/MainActionTests.java

@@ -32,6 +32,7 @@
 
 package org.opensearch.action.main;
 
+import org.opensearch.LegacyESVersion;
 import org.opensearch.action.ActionListener;
 import org.opensearch.action.support.ActionFilters;
 import org.opensearch.cluster.ClusterName;
@@ -55,6 +56,7 @@
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
+import static org.opensearch.action.main.TransportMainAction.OVERRIDE_MAIN_RESPONSE_VERSION_KEY;
 
 public class MainActionTests extends OpenSearchTestCase {
 
@@ -128,4 +130,45 @@ public void onFailure(Exception e) {
         assertNotNull(responseRef.get());
         verify(clusterService, times(1)).state();
     }
+
+    public void testMainResponseVersionOverrideEnabledByConfigSetting() {
+        final ClusterName clusterName = new ClusterName("opensearch");
+        ClusterState state = ClusterState.builder(clusterName).blocks(mock(ClusterBlocks.class)).build();
+
+        final ClusterService clusterService = mock(ClusterService.class);
+        when(clusterService.state()).thenReturn(state);
+        when(clusterService.getClusterSettings()).thenReturn(
+            new ClusterSettings(Settings.EMPTY, ClusterSettings.BUILT_IN_CLUSTER_SETTINGS)
+        );
+
+        TransportService transportService = new TransportService(
+            Settings.EMPTY,
+            mock(Transport.class),
+            null,
+            TransportService.NOOP_TRANSPORT_INTERCEPTOR,
+            x -> null,
+            null,
+            Collections.emptySet()
+        );
+
+        final Settings settings = Settings.builder().put("node.name", "my-node").put(OVERRIDE_MAIN_RESPONSE_VERSION_KEY, true).build();
+
+        TransportMainAction action = new TransportMainAction(settings, transportService, mock(ActionFilters.class), clusterService);
+        AtomicReference<MainResponse> responseRef = new AtomicReference<>();
+        action.doExecute(mock(Task.class), new MainRequest(), new ActionListener<MainResponse>() {
+            @Override
+            public void onResponse(MainResponse mainResponse) {
+                responseRef.set(mainResponse);
+            }
+
+            @Override
+            public void onFailure(Exception e) {
+                logger.error("unexpected error", e);
+            }
+        });
+
+        final MainResponse mainResponse = responseRef.get();
+        assertEquals(LegacyESVersion.V_7_10_2.toString(), mainResponse.getVersionNumber());
+        assertWarnings(TransportMainAction.OVERRIDE_MAIN_RESPONSE_VERSION_DEPRECATION_MESSAGE);
+    }
 }

server/src/test/java/org/opensearch/action/main/MainResponseTests.java

@@ -138,6 +138,22 @@ public void testToXContent() throws IOException {
         );
     }
 
+    public void toXContent_overrideMainResponseVersion() throws IOException {
+        String responseVersion = LegacyESVersion.V_7_10_2.toString();
+        MainResponse response = new MainResponse(
+            "nodeName",
+            Version.CURRENT,
+            new ClusterName("clusterName"),
+            randomAlphaOfLengthBetween(10, 20),
+            Build.CURRENT,
+            responseVersion
+        );
+        XContentBuilder builder = XContentFactory.jsonBuilder();
+        response.toXContent(builder, ToXContent.EMPTY_PARAMS);
+        assertTrue(Strings.toString(builder).contains("\"number\":\"" + responseVersion + "\","));
+        assertFalse(Strings.toString(builder).contains("\"distribution\":\"" + Build.CURRENT.getDistribution() + "\","));
+    }
+
     @Override
     protected MainResponse mutateInstance(MainResponse mutateInstance) {
         String clusterUuid = mutateInstance.getClusterUuid();