BE: Exclude offline nodes from target calculation when adjusting the replication factor

api/src/main/java/io/kafbat/ui/service/TopicsService.java

@@ -26,6 +26,7 @@
 import io.kafbat.ui.model.TopicCreationDTO;
 import io.kafbat.ui.model.TopicUpdateDTO;
 import java.time.Duration;
+import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Comparator;
@@ -288,6 +289,18 @@ private Map<TopicPartition, Optional<NewPartitionReassignment>> getPartitionsRea
     Map<Integer, Integer> brokersUsage = getBrokersMap(cluster, currentAssignment);
     int currentReplicationFactor = topic.getReplicationFactor();
 
+    // Get online nodes
+    List<Integer> onlineNodes = statisticsCache.get(cluster).getClusterDescription().getNodes()
+        .stream().map(Node::id).toList();
+
+    // keep only online nodes
+    for (Map.Entry<Integer, List<Integer>> parition : currentAssignment.entrySet()) {
+      parition.getValue().retainAll(onlineNodes);
+    }
+
+    brokersUsage.keySet().retainAll(onlineNodes);
+
+
     // If we should to increase Replication factor
     if (replicationFactorChange.getTotalReplicationFactor() > currentReplicationFactor) {
       // For each partition
@@ -320,28 +333,35 @@ private Map<TopicPartition, Optional<NewPartitionReassignment>> getPartitionsRea
         var partition = assignmentEntry.getKey();
         var brokers = assignmentEntry.getValue();
 
+        // Copy from online nodes if all nodes are offline
+        if (brokers.isEmpty()) {
+          brokers = new ArrayList<>(onlineNodes);
+        }
+
         // Get brokers list sorted by usage in reverse order
         var brokersUsageList = brokersUsage.entrySet().stream()
             .sorted(Map.Entry.comparingByValue(Comparator.reverseOrder()))
             .map(Map.Entry::getKey)
             .toList();
 
+        Integer leader = topic.getPartitions().get(partition).getLeader();
+
         // Iterate brokers and try to remove them from assignment
         // while partition replicas count != requested replication factor
         for (Integer broker : brokersUsageList) {
+          if (brokers.size() == replicationFactorChange.getTotalReplicationFactor()) {
+            break;
+          }
           // Check is the broker the leader of partition
-          if (!topic.getPartitions().get(partition).getLeader()
-              .equals(broker)) {
+          if (leader == null || !leader.equals(broker)) {
             brokers.remove(broker);
             brokersUsage.merge(broker, -1, Integer::sum);
           }
-          if (brokers.size() == replicationFactorChange.getTotalReplicationFactor()) {
-            break;
-          }
         }
         if (brokers.size() != replicationFactorChange.getTotalReplicationFactor()) {
           throw new ValidationException("Something went wrong during removing replicas");
         }
+        currentAssignment.put(partition, brokers);
       }
     } else {
       throw new ValidationException("Replication factor already equals requested");
@@ -374,7 +394,7 @@ private Map<Integer, Integer> getBrokersMap(KafkaCluster cluster,
             c -> 0
         ));
     currentAssignment.values().forEach(brokers -> brokers
-        .forEach(broker -> result.put(broker, result.get(broker) + 1)));
+        .forEach(broker -> result.put(broker, result.getOrDefault(broker, 0) + 1)));
 
     return result;
   }