Fixed - failover isn't handled correctly in some cases. #5018

redisson/src/main/java/org/redisson/cluster/ClusterConnectionManager.java

@@ -496,7 +496,12 @@ public class ClusterConnectionManager extends MasterSlaveConnectionManager {
             futures.add(f);
         }
         return CompletableFuture.allOf(futures.toArray(new CompletableFuture[0]))
-                                    .exceptionally(e -> null);
+                                    .exceptionally(e -> {
+                                        if (e != null) {
+                                            log.error(e.getMessage(), e);
+                                        }
+                                        return null;
+                                    });
     }
 
     private CompletableFuture<Void> upDownSlaves(MasterSlaveEntry entry, ClusterPartition currentPart, ClusterPartition newPart, Set<RedisURI> addedSlaves) {
@@ -576,17 +581,13 @@ public class ClusterConnectionManager extends MasterSlaveConnectionManager {
             }
 
             CompletableFuture<Void> slaveUpFuture = entry.addSlave(uri, false, NodeType.SLAVE, configEndpointHostName);
-            slaveUpFuture = slaveUpFuture.whenComplete((res, ex) -> {
-                if (ex != null) {
-                    log.error("Can't add slave: {}", uri, ex);
-                }
-            }).thenCompose(res -> {
+            CompletableFuture<Void> f = slaveUpFuture.thenCompose(res -> {
                 currentPart.addSlaveAddress(uri);
                 log.info("slave: {} added for slot ranges: {}", uri, currentPart.getSlotRanges());
                 return entry.excludeMasterFromSlaves(uri)
                         .thenApply(r -> null);
             });
-            futures.add(slaveUpFuture);
+            futures.add(f);
         }
 
         CompletableFuture<Void> f = CompletableFuture.allOf(futures.toArray(new CompletableFuture[0]));
@@ -649,7 +650,12 @@ public class ClusterConnectionManager extends MasterSlaveConnectionManager {
             futures.add(future.toCompletableFuture());
         }
         return CompletableFuture.allOf(futures.toArray(new CompletableFuture[0]))
-                                    .exceptionally(e -> null);
+                                    .exceptionally(e -> {
+                                        if (e != null) {
+                                            log.error(e.getMessage(), e);
+                                        }
+                                        return null;
+                                    });
     }
 
     private void checkSlotsChange(Collection<ClusterPartition> newPartitions) {