Update TransportNodesCapabilitiesAction for V9

libs/core/src/main/java/org/elasticsearch/core/RestApiVersion.java

@@ -61,15 +61,11 @@ public static Predicate<RestApiVersion> onOrAfter(RestApiVersion restApiVersion)
         };
     }
 
-    public static RestApiVersion forMajor(int major) {
-        switch (major) {
-            case 8 -> {
-                return V_8;
-            }
-            case 9 -> {
-                return V_9;
-            }
-            default -> throw new IllegalArgumentException("Unknown REST API version " + major);
-        }
+    public static RestApiVersion forMajorIfKnown(int major) {
+        return switch (major) {
+            case 8 -> V_8;
+            case 9 -> V_9;
+            default -> null;
+        };
     }
 }

server/src/internalClusterTest/java/org/elasticsearch/nodescapabilities/SimpleNodesCapabilitiesIT.java

@@ -12,6 +12,7 @@
 import org.elasticsearch.action.admin.cluster.health.ClusterHealthResponse;
 import org.elasticsearch.action.admin.cluster.node.capabilities.NodesCapabilitiesRequest;
 import org.elasticsearch.action.admin.cluster.node.capabilities.NodesCapabilitiesResponse;
+import org.elasticsearch.core.RestApiVersion;
 import org.elasticsearch.test.ESIntegTestCase;
 
 import java.io.IOException;
@@ -43,6 +44,13 @@ public void testNodesCapabilities() throws IOException {
         assertThat(response.getNodes(), hasSize(2));
         assertThat(response.isSupported(), isPresentWith(true));
 
+        // check we support REST API version parameters of the capabilities API
+        response = clusterAdmin().nodesCapabilities(new NodesCapabilitiesRequest().path("_capabilities").parameters("method", "path")
+                .restApiVersion(RestApiVersion.current()))
+            .actionGet();
+        assertThat(response.getNodes(), hasSize(2));
+        assertThat(response.isSupported(), isPresentWith(true));
+
         // check we don't support some other parameters of the capabilities API
         response = clusterAdmin().nodesCapabilities(new NodesCapabilitiesRequest().path("_capabilities").parameters("method", "invalid"))
             .actionGet();

server/src/main/java/org/elasticsearch/action/admin/cluster/node/capabilities/NodesCapabilitiesRequest.java

@@ -22,7 +22,7 @@ public class NodesCapabilitiesRequest extends BaseNodesRequest {
     private String path = "/";
     private Set<String> parameters = Set.of();
     private Set<String> capabilities = Set.of();
-    private RestApiVersion restApiVersion = RestApiVersion.current();
+    private RestApiVersion restApiVersion = null;
 
     public NodesCapabilitiesRequest() {
         // send to all nodes

server/src/main/java/org/elasticsearch/action/admin/cluster/node/capabilities/TransportNodesCapabilitiesAction.java

@@ -93,17 +93,19 @@ protected NodeCapability nodeOperation(NodeCapabilitiesRequest request, Task tas
             request.path,
             request.parameters,
             request.capabilities,
-            request.restApiVersion
+            request.restApiVersionMajor
         );
         return new NodeCapability(supported, transportService.getLocalNode());
     }
 
     public static class NodeCapabilitiesRequest extends TransportRequest {
+        private static final int IMPLICIT_REST_API_VERSION = 0;
+
         private final RestRequest.Method method;
         private final String path;
         private final Set<String> parameters;
         private final Set<String> capabilities;
-        private final RestApiVersion restApiVersion;
+        private final Byte restApiVersionMajor;
 
         public NodeCapabilitiesRequest(StreamInput in) throws IOException {
             super(in);
@@ -112,7 +114,8 @@ public NodeCapabilitiesRequest(StreamInput in) throws IOException {
             path = in.readString();
             parameters = in.readCollectionAsImmutableSet(StreamInput::readString);
             capabilities = in.readCollectionAsImmutableSet(StreamInput::readString);
-            restApiVersion = RestApiVersion.forMajor(in.readVInt());
+            byte versionFromMessage = (byte) in.readVInt();
+            restApiVersionMajor = (versionFromMessage != IMPLICIT_REST_API_VERSION) ? versionFromMessage : null;
         }
 
         public NodeCapabilitiesRequest(
@@ -126,7 +129,7 @@ public NodeCapabilitiesRequest(
             this.path = path;
             this.parameters = Set.copyOf(parameters);
             this.capabilities = Set.copyOf(capabilities);
-            this.restApiVersion = restApiVersion;
+            this.restApiVersionMajor = (restApiVersion != null) ? restApiVersion.major : null;
         }
 
         @UpdateForV9(owner = UpdateForV9.Owner.CORE_INFRA) // 8.x blows up in a mixed cluster when trying to read RestApiVersion.forMajor(9)
@@ -141,9 +144,11 @@ public void writeTo(StreamOutput out) throws IOException {
             out.writeString(path);
             out.writeCollection(parameters, StreamOutput::writeString);
             out.writeCollection(capabilities, StreamOutput::writeString);
-            // Fixme: lies! all lies!
-            out.writeVInt(8);
-            // out.writeVInt(restApiVersion.major);
+            if (restApiVersionMajor == null) {
+                out.writeVInt(IMPLICIT_REST_API_VERSION);
+            } else {
+                out.writeVInt(restApiVersionMajor);
+            }
         }
     }
 }

server/src/main/java/org/elasticsearch/rest/RestController.java

@@ -350,8 +350,14 @@ public boolean checkSupported(
         String path,
         Set<String> parameters,
         Set<String> capabilities,
-        RestApiVersion restApiVersion
+        Byte restApiVersionMajor
     ) {
+        RestApiVersion restApiVersion = getRestApiVersionIfKnown(restApiVersionMajor);
+        // if explicitly requested RestApiVersion is not known by this node, it should respond that it doesn't support the capability
+        if (restApiVersion == null) {
+            return false;
+        }
+
         Iterator<MethodHandlers> allHandlers = getAllHandlers(null, path);
         while (allHandlers.hasNext()) {
             RestHandler handler;
@@ -373,6 +379,16 @@ public boolean checkSupported(
         return false;
     }
 
+    private static RestApiVersion getRestApiVersionIfKnown(Byte restApiVersionMajor) {
+        RestApiVersion restApiVersion;
+        if (restApiVersionMajor == null) {
+            restApiVersion = RestApiVersion.current();
+        } else {
+            restApiVersion = RestApiVersion.forMajorIfKnown(restApiVersionMajor);
+        }
+        return restApiVersion;
+    }
+
     @Override
     public Map<String, HttpRouteStats> getStats() {
         final Iterator<MethodHandlers> methodHandlersIterator = handlers.allNodeValues();

server/src/main/java/org/elasticsearch/rest/action/admin/cluster/RestNodesCapabilitiesAction.java

@@ -66,8 +66,11 @@ protected RestChannelConsumer prepareRequest(RestRequest request, NodeClient cli
         NodesCapabilitiesRequest r = requestNodes.method(RestRequest.Method.valueOf(request.param("method", "GET")))
             .path(path)
             .parameters(request.paramAsStringArray("parameters", Strings.EMPTY_ARRAY))
-            .capabilities(request.paramAsStringArray("capabilities", Strings.EMPTY_ARRAY))
-            .restApiVersion(request.getRestApiVersion());
+            .capabilities(request.paramAsStringArray("capabilities", Strings.EMPTY_ARRAY));
+
+        if (request.hasExplicitRestApiVersion()) {
+            r.restApiVersion(request.getRestApiVersion());
+        }
 
         return channel -> client.admin().cluster().nodesCapabilities(r, new NodesResponseRestListener<>(channel));
     }