Fix: tag name and adds lagging reason

Signed-off-by: Bhumika Sharma <bhumikka@amazon.com>

Author: Bhumika Sharma

server/src/main/java/org/opensearch/cluster/ClusterManagerMetrics.java

@@ -23,7 +23,7 @@
  */
 public final class ClusterManagerMetrics {
 
-    public static final String NODE_ID_TAG = "follower_node_id";
+    public static final String FOLLOWER_NODE_ID_TAG = "follower_node_id";
     public static final String REASON_TAG = "reason";
     private static final String LATENCY_METRIC_UNIT_MS = "ms";
     private static final String COUNTER_METRICS_UNIT = "1";

server/src/main/java/org/opensearch/cluster/coordination/Coordinator.java

@@ -112,11 +112,12 @@
 import java.util.stream.Stream;
 import java.util.stream.StreamSupport;
 
-import static org.opensearch.cluster.ClusterManagerMetrics.NODE_ID_TAG;
+import static org.opensearch.cluster.ClusterManagerMetrics.FOLLOWER_NODE_ID_TAG;
 import static org.opensearch.cluster.ClusterManagerMetrics.REASON_TAG;
 import static org.opensearch.cluster.coordination.FollowersChecker.NODE_LEFT_REASON_DISCONNECTED;
 import static org.opensearch.cluster.coordination.FollowersChecker.NODE_LEFT_REASON_FOLLOWER_CHECK_RETRY_FAIL;
 import static org.opensearch.cluster.coordination.FollowersChecker.NODE_LEFT_REASON_HEALTHCHECK_FAIL;
+import static org.opensearch.cluster.coordination.FollowersChecker.NODE_LEFT_REASON_LAGGING;
 import static org.opensearch.cluster.coordination.NoClusterManagerBlockService.NO_CLUSTER_MANAGER_BLOCK_ID;
 import static org.opensearch.cluster.decommission.DecommissionHelper.nodeCommissioned;
 import static org.opensearch.gateway.ClusterStateUpdaters.hideStateIfNotRecovered;
@@ -369,14 +370,15 @@ private void removeNode(DiscoveryNode discoveryNode, String reason) {
                 );
                 String reasonToPublish = switch (reason) {
                     case NODE_LEFT_REASON_DISCONNECTED -> "disconnected";
+                    case NODE_LEFT_REASON_LAGGING -> "lagging";
                     case NODE_LEFT_REASON_FOLLOWER_CHECK_RETRY_FAIL -> "follower.check.fail";
                     case NODE_LEFT_REASON_HEALTHCHECK_FAIL -> "health.check.fail";
                     default -> reason;
                 };
                 clusterManagerMetrics.incrementCounter(
                     clusterManagerMetrics.nodeLeftCounter,
                     1.0,
-                    Optional.ofNullable(Tags.create().addTag(NODE_ID_TAG, discoveryNode.getId()).addTag(REASON_TAG, reasonToPublish))
+                    Optional.ofNullable(Tags.create().addTag(FOLLOWER_NODE_ID_TAG, discoveryNode.getId()).addTag(REASON_TAG, reasonToPublish))
                 );
             }
         }

server/src/main/java/org/opensearch/cluster/coordination/FollowersChecker.java

@@ -86,6 +86,7 @@ public class FollowersChecker {
     private static final Logger logger = LogManager.getLogger(FollowersChecker.class);
 
     public static final String FOLLOWER_CHECK_ACTION_NAME = "internal:coordination/fault_detection/follower_check";
+    public static final String NODE_LEFT_REASON_LAGGING = "lagging";
     public static final String NODE_LEFT_REASON_DISCONNECTED = "disconnected";
     public static final String NODE_LEFT_REASON_HEALTHCHECK_FAIL = "health check failed";
     public static final String NODE_LEFT_REASON_FOLLOWER_CHECK_RETRY_FAIL = "followers check retry count exceeded";