Add a new node role - remote searcher

Signed-off-by: Tianli Feng <ftianli@amazon.com>

client/rest/src/main/java/org/opensearch/client/Node.java

@@ -239,6 +239,13 @@ public boolean isIngest() {
             return roles.contains("ingest");
         }
 
+        /**
+         * Returns whether the node provides search capability for a remote shard.
+         */
+        public boolean isRemoteSearcher() {
+            return roles.contains("remote_searcher");
+        }
+
         @Override
         public String toString() {
             return String.join(",", roles);

client/rest/src/test/java/org/opensearch/client/NodeTests.java

@@ -48,7 +48,9 @@
 import static java.util.Collections.singletonMap;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
+import static org.hamcrest.CoreMatchers.equalTo;
 
 public class NodeTests extends RestClientTestCase {
     public void testToString() {
@@ -161,4 +163,9 @@ public void testEqualsAndHashCode() {
             )
         );
     }
+
+    public void testIsRemoteSearcherNode() {
+        Roles remoteSearcherRole = new Roles(Collections.singleton("remote_searcher"));
+        assertThat(remoteSearcherRole.isRemoteSearcher(), equalTo(true));
+    }
 }

server/src/internalClusterTest/java/org/opensearch/action/admin/cluster/stats/ClusterStatsIT.java

@@ -89,6 +89,7 @@ public void testNodeCounts() {
         expectedCounts.put(DiscoveryNodeRole.CLUSTER_MANAGER_ROLE.roleName(), 1);
         expectedCounts.put(DiscoveryNodeRole.INGEST_ROLE.roleName(), 1);
         expectedCounts.put(DiscoveryNodeRole.REMOTE_CLUSTER_CLIENT_ROLE.roleName(), 1);
+        expectedCounts.put(DiscoveryNodeRole.REMOTE_SEARCHER_ROLE.roleName(), 0);
         expectedCounts.put(ClusterStatsNodes.Counts.COORDINATING_ONLY, 0);
         int numNodes = randomIntBetween(1, 5);
 

server/src/main/java/org/opensearch/cluster/node/DiscoveryNode.java

@@ -498,6 +498,15 @@ public boolean isRemoteClusterClient() {
         return roles.contains(DiscoveryNodeRole.REMOTE_CLUSTER_CLIENT_ROLE);
     }
 
+    /**
+     * Returns whether the node can provide search capability for a remote shard.
+     *
+     * @return true if the node contains remote_searcher role, false otherwise
+     */
+    public boolean isRemoteSearcherNode() {
+        return roles.contains(DiscoveryNodeRole.REMOTE_SEARCHER_ROLE);
+    }
+
     /**
      * Returns a set of all the roles that the node has. The roles are returned in sorted order by the role name.
      * <p>

server/src/main/java/org/opensearch/cluster/node/DiscoveryNodeRole.java

@@ -290,11 +290,33 @@ public Setting<Boolean> legacySetting() {
 
     };
 
+    /**
+     * Represents the role for a remote searcher node.
+     */
+    public static final DiscoveryNodeRole REMOTE_SEARCHER_ROLE = new DiscoveryNodeRole("remote_searcher", "s", true) {
+
+        @Override
+        public Setting<Boolean> legacySetting() {
+            // remote_searcher role is added in 2.4 so doesn't need to configure legacy setting
+            return null;
+        }
+
+        @Override
+        public DiscoveryNodeRole getCompatibilityRole(Version nodeVersion) {
+            if (nodeVersion.onOrAfter(Version.V_2_4_0)) {
+                return this;
+            } else {
+                return DiscoveryNodeRole.DATA_ROLE;
+            }
+        }
+
+    };
+
     /**
      * The built-in node roles.
      */
     public static SortedSet<DiscoveryNodeRole> BUILT_IN_ROLES = Collections.unmodifiableSortedSet(
-        new TreeSet<>(Arrays.asList(DATA_ROLE, INGEST_ROLE, CLUSTER_MANAGER_ROLE, REMOTE_CLUSTER_CLIENT_ROLE))
+        new TreeSet<>(Arrays.asList(DATA_ROLE, INGEST_ROLE, CLUSTER_MANAGER_ROLE, REMOTE_CLUSTER_CLIENT_ROLE, REMOTE_SEARCHER_ROLE))
     );
 
     /**

server/src/test/java/org/opensearch/cluster/node/DiscoveryNodeTests.java

@@ -39,6 +39,7 @@
 import org.opensearch.common.settings.Setting;
 import org.opensearch.common.settings.Settings;
 import org.opensearch.common.transport.TransportAddress;
+import org.opensearch.test.NodeRoles;
 import org.opensearch.test.OpenSearchTestCase;
 
 import java.net.InetAddress;
@@ -204,4 +205,10 @@ public void testGetRoleFromRoleNameIsCaseInsensitive() {
         assertEquals(dynamicRoleName.toLowerCase(Locale.ROOT), dynamicNodeRole.roleName());
         assertEquals(dynamicRoleName.toLowerCase(Locale.ROOT), dynamicNodeRole.roleNameAbbreviation());
     }
+
+    public void testDiscoveryNodeIsRemoteSearcherNode() {
+        final Settings settingWithRemoteSearcherRole = NodeRoles.onlyRole(DiscoveryNodeRole.REMOTE_SEARCHER_ROLE);
+        final DiscoveryNode node = DiscoveryNode.createLocal(settingWithRemoteSearcherRole, buildNewFakeTransportAddress(), "node");
+        assertThat(node.isRemoteSearcherNode(), equalTo(true));
+    }
 }