Restore DataNode removal cleanup after child procedure failures (#18947)

Allow STOP_DATA_NODE rollback cleanup under the commit-point guard.
Preserve execution retries and verify transient cleanup failures stay retryable.

Author: d-wang-commit

iotdb-core/confignode/src/main/java/org/apache/iotdb/confignode/procedure/impl/node/RemoveDataNodesProcedure.java

@@ -158,19 +158,16 @@ protected Flow executeFromState(ConfigNodeProcedureEnv env, RemoveDataNodeState
           return Flow.NO_MORE_STATE;
       }
     } catch (Exception e) {
-      if (isRollbackSupported(state)) {
-        setFailure(new ProcedureException(ProcedureMessages.REMOVE_DATA_NODE_FAILED + state));
+      // Rollback support permits failure cleanup; transient execution errors still retry here.
+      LOG.error(
+          ProcedureMessages.LOG_RETRIEVABLE_ERROR_TRYING_REMOVE_DATA_NODE_ARG_STATE_ARG_4EFEB850,
+          removedDataNodes,
+          state,
+          e);
+      if (getCycles() > RETRY_THRESHOLD) {
+        setFailure(new ProcedureException(ProcedureMessages.STATE_STUCK_AT + state));
       } else {
-        LOG.error(
-            ProcedureMessages.LOG_RETRIEVABLE_ERROR_TRYING_REMOVE_DATA_NODE_ARG_STATE_ARG_4EFEB850,
-            removedDataNodes,
-            state,
-            e);
-        if (getCycles() > RETRY_THRESHOLD) {
-          setFailure(new ProcedureException(ProcedureMessages.STATE_STUCK_AT + state));
-        } else {
-          setNextState(state);
-        }
+        setNextState(state);
       }
     }
     return Flow.HAS_MORE_STATE;
@@ -291,7 +288,9 @@ protected long getRollbackRetryTimeout() {
 
   @Override
   protected boolean isRollbackSupported(RemoveDataNodeState state) {
-    return false;
+    // A failed migration child must still trigger node cleanup. This restores node statuses and
+    // stops drained nodes without undoing completed region migrations.
+    return state == RemoveDataNodeState.STOP_DATA_NODE;
   }
 
   /**

iotdb-core/confignode/src/test/java/org/apache/iotdb/confignode/procedure/impl/node/RemoveDataNodePersistenceTest.java

@@ -420,12 +420,14 @@ public void testProcedureExecutorCanActuallyRetryCompensationCommitFailure() thr
     failStatusWrite = true;
     TestProcedure procedure = procedure(NodeStatus.Running, RemoveDataNodeState.STOP_DATA_NODE);
     procedure.step(env);
+    assertFalse("A transient cleanup failure must remain retryable", procedure.isFailed());
     assertEquals(
         "The state-machine executor must retain the failed compensation step",
         RemoveDataNodeState.STOP_DATA_NODE,
         procedure.state());
     failStatusWrite = false;
     procedure.step(env);
+    assertFalse("Successful cleanup retry must not leave a failure", procedure.isFailed());
     assertStates(FIRST, NodeStatus.Running, NodeStatus.Running, null);
   }