Add cluster setting to spoof version number returned from MainResponse (#847)

This change adds a new cluster setting "compatibility.override_main_response_version"
that when enabled spoofs the version.number returned from MainResponse
for REST clients expecting legacy version 7.10.2.

Signed-off-by: Marc Handalian <handalm@amazon.com>

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 class PingAndInfoIT extends OpenSearchRestHighLevelClientTestCase {
         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

@@ -55,6 +55,7 @@ public class MainResponse extends ActionResponse implements ToXContentObject {
     private ClusterName clusterName;
     private String clusterUuid;
     private Build build;
+    private String versionNumber;
 
     MainResponse() {}
 
@@ -68,6 +69,7 @@ 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) {
@@ -76,6 +78,17 @@ public class MainResponse extends ActionResponse implements ToXContentObject {
         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() {
@@ -99,6 +112,10 @@ public class MainResponse extends ActionResponse implements ToXContentObject {
         return build;
     }
 
+    public String getVersionNumber() {
+        return versionNumber;
+    }
+
     @Override
     public void writeTo(StreamOutput out) throws IOException {
         out.writeString(nodeName);
@@ -123,7 +140,7 @@ public class MainResponse extends ActionResponse implements ToXContentObject {
         builder.field("cluster_uuid", clusterUuid);
         builder.startObject("version")
             .field("distribution", build.getDistribution())
-            .field("number", build.getQualifiedVersion())
+            .field("number", versionNumber)
             .field("build_type", build.type().displayName())
             .field("build_hash", build.hash())
             .field("build_date", build.date())
@@ -163,6 +180,7 @@ public class MainResponse extends ActionResponse implements ToXContentObject {
                     .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

@@ -33,6 +33,7 @@
 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;
@@ -40,6 +41,8 @@ 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;
@@ -47,8 +50,19 @@ import org.opensearch.transport.TransportService;
 
 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(Settings settings, TransportService transportService,
@@ -56,6 +70,19 @@ public class TransportMainAction extends HandledTransportAction<MainRequest, Mai
         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
@@ -63,6 +90,6 @@ public class TransportMainAction extends HandledTransportAction<MainRequest, Mai
         ClusterState clusterState = clusterService.state();
         listener.onResponse(
             new MainResponse(nodeName, Version.CURRENT, clusterState.getClusterName(),
-                    clusterState.metadata().clusterUUID(), Build.CURRENT));
+                    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.watcher.ResourceWatcherService;
 import org.opensearch.action.admin.cluster.configuration.TransportAddVotingConfigExclusionsAction;
 import org.opensearch.action.admin.indices.close.TransportCloseIndexAction;
@@ -577,6 +578,7 @@ public final class ClusterSettings extends AbstractScopedSettings {
             FsHealthService.ENABLED_SETTING,
             FsHealthService.REFRESH_INTERVAL_SETTING,
             FsHealthService.SLOW_PATH_LOGGING_THRESHOLD_SETTING,
+            TransportMainAction.OVERRIDE_MAIN_RESPONSE_VERSION,
             IndexingPressure.MAX_INDEXING_BYTES)));
 
     public static List<SettingUpgrader<?>> BUILT_IN_SETTING_UPGRADERS = Collections.unmodifiableList(Arrays.asList(

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;
@@ -40,6 +41,7 @@ import org.opensearch.cluster.block.ClusterBlock;
 import org.opensearch.cluster.block.ClusterBlockLevel;
 import org.opensearch.cluster.block.ClusterBlocks;
 import org.opensearch.cluster.service.ClusterService;
+import org.opensearch.common.settings.ClusterSettings;
 import org.opensearch.common.settings.Settings;
 import org.opensearch.rest.RestStatus;
 import org.opensearch.tasks.Task;
@@ -54,6 +56,7 @@ import static org.mockito.Mockito.mock;
 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 {
 
@@ -61,6 +64,8 @@ public class MainActionTests extends OpenSearchTestCase {
         final ClusterService clusterService = mock(ClusterService.class);
         final ClusterName clusterName = new ClusterName("opensearch");
         final Settings settings = Settings.builder().put("node.name", "my-node").build();
+        when(clusterService.getClusterSettings()).thenReturn(new ClusterSettings(Settings.EMPTY,
+            ClusterSettings.BUILT_IN_CLUSTER_SETTINGS));
         ClusterBlocks blocks;
         if (randomBoolean()) {
             if (randomBoolean()) {
@@ -99,4 +104,40 @@ public class MainActionTests extends OpenSearchTestCase {
         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

@@ -102,6 +102,15 @@ public class MainResponseTests extends AbstractSerializingTestCase<MainResponse>
           + "}", Strings.toString(builder));
     }
 
+    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 + "\","));
+    }
+
     @Override
     protected MainResponse mutateInstance(MainResponse mutateInstance) {
         String clusterUuid = mutateInstance.getClusterUuid();