Add a new node role 'search' which is dedicated to provide search capability (#4689)

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

Author: Tianli Feng

CHANGELOG.md

@@ -35,6 +35,7 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 - Added precommit support for MacOS ([#4682](https://github.com/opensearch-project/OpenSearch/pull/4682))
 - Recommission API changes for service layer ([#4320](https://github.com/opensearch-project/OpenSearch/pull/4320))
 - Update GeoGrid base class access modifier to support extensibility ([#4572](https://github.com/opensearch-project/OpenSearch/pull/4572))
+- Add a new node role 'search' which is dedicated to provide search capability ([#4689](https://github.com/opensearch-project/OpenSearch/pull/4689))
 
 ### Dependencies
 - Bumps `log4j-core` from 2.18.0 to 2.19.0

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 is dedicated to provide search capability.
+         */
+        public boolean isSearch() {
+            return roles.contains("search");
+        }
+
         @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 testIsSearchNode() {
+        Roles searchRole = new Roles(Collections.singleton("search"));
+        assertThat(searchRole.isSearch(), 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.SEARCH_ROLE.roleName(), 0);
         expectedCounts.put(ClusterStatsNodes.Counts.COORDINATING_ONLY, 0);
         int numNodes = randomIntBetween(1, 5);
 
@@ -160,6 +161,7 @@ public void testNodeCountsWithDeprecatedMasterRole() {
         expectedCounts.put(DiscoveryNodeRole.CLUSTER_MANAGER_ROLE.roleName(), 1);
         expectedCounts.put(DiscoveryNodeRole.INGEST_ROLE.roleName(), 0);
         expectedCounts.put(DiscoveryNodeRole.REMOTE_CLUSTER_CLIENT_ROLE.roleName(), 0);
+        expectedCounts.put(DiscoveryNodeRole.SEARCH_ROLE.roleName(), 0);
         expectedCounts.put(ClusterStatsNodes.Counts.COORDINATING_ONLY, 0);
 
         ClusterStatsResponse response = client().admin().cluster().prepareClusterStats().get();

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

@@ -460,6 +460,15 @@ public boolean isRemoteClusterClient() {
         return roles.contains(DiscoveryNodeRole.REMOTE_CLUSTER_CLIENT_ROLE);
     }
 
+    /**
+     * Returns whether the node is dedicated to provide search capability.
+     *
+     * @return true if the node contains search role, false otherwise
+     */
+    public boolean isSearchNode() {
+        return roles.contains(DiscoveryNodeRole.SEARCH_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 +290,24 @@ public Setting<Boolean> legacySetting() {
 
     };
 
+    /**
+     * Represents the role for a search node, which is dedicated to provide search capability.
+     */
+    public static final DiscoveryNodeRole SEARCH_ROLE = new DiscoveryNodeRole("search", "s", true) {
+
+        @Override
+        public Setting<Boolean> legacySetting() {
+            // search role is added in 2.4 so doesn't need to configure legacy setting
+            return null;
+        }
+
+    };
+
     /**
      * 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, SEARCH_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 testDiscoveryNodeIsSearchNode() {
+        final Settings settingWithSearchRole = NodeRoles.onlyRole(DiscoveryNodeRole.SEARCH_ROLE);
+        final DiscoveryNode node = DiscoveryNode.createLocal(settingWithSearchRole, buildNewFakeTransportAddress(), "node");
+        assertThat(node.isSearchNode(), equalTo(true));
+    }
 }