IGNITE-27108 Added client router node metric. (#12520)

Author: NSAmelchev

modules/core/src/main/java/org/apache/ignite/spi/discovery/tcp/TcpDiscoverySpi.java

@@ -1500,7 +1500,10 @@ public long getCoordinatorSinceTimestamp() {
 
             discoReg.register("CoordinatorSince", stats::coordinatorSinceTimestamp, "Coordinator since timestamp");
         }
-
+        else {
+            discoReg.register("ClientRouterNodeId", () -> String.valueOf(locNode.clientRouterNodeId()), String.class,
+                "Client router node ID.");
+        }
     }
 
     /** {@inheritDoc} */

modules/core/src/test/java/org/apache/ignite/spi/discovery/datacenter/MultiDataCenterClientRoutingTest.java

@@ -28,10 +28,13 @@
 import org.apache.ignite.internal.IgniteEx;
 import org.apache.ignite.internal.IgniteNodeAttributes;
 import org.apache.ignite.internal.TestRecordingCommunicationSpi;
+import org.apache.ignite.internal.processors.metric.MetricRegistryImpl;
 import org.apache.ignite.spi.discovery.tcp.internal.TcpDiscoveryNode;
 import org.apache.ignite.testframework.junits.common.GridCommonAbstractTest;
 import org.junit.Test;
 
+import static org.apache.ignite.internal.managers.discovery.GridDiscoveryManager.DISCO_METRICS;
+
 /** */
 public class MultiDataCenterClientRoutingTest extends GridCommonAbstractTest {
     /** */
@@ -88,6 +91,9 @@ public void testConnectionToProperDc() throws Exception {
         IgniteEx client = startClientGrid();
 
         UUID routerId = ((TcpDiscoveryNode)client.localNode()).clientRouterNodeId();
+        MetricRegistryImpl mreg = client.context().metric().registry(DISCO_METRICS);
+
+        assertEquals(routerId.toString(), mreg.findMetric("ClientRouterNodeId").getAsString());
 
         List<ClusterNode> routers = client.cluster().nodes().stream()
             .filter(node -> node.id().equals(routerId))