NIFI-12991 Fixed Recursive Validation of Group Execution Engine (#9186)

Fixed issue in which we recursively validate that we can change Execution Engine of a group, but without changing the top level, inherited groups can't actually be changed; instead, replaced logic to ensure that we can change the top level, that we don't validate the constraint that a STATELESS group cannot have a STATEFUL child, and then validate that all descendant groups can be updated, but without checking the descendants' parent groups.

Signed-off-by: David Handermann <exceptionfactory@apache.org>

nifi-framework-bundle/nifi-framework/nifi-framework-components/src/main/java/org/apache/nifi/groups/StandardProcessGroup.java

@@ -4406,6 +4406,23 @@ public void verifyCanSetExecutionEngine(final ExecutionEngine executionEngine) {
             }
         }
 
+        // Ensure that we are not changing a parent to Stateless when a child is explicitly set to STANDARD.
+        if (resolvedProposedEngine == ExecutionEngine.STATELESS) {
+            for (final ProcessGroup descendant : findAllProcessGroups()) {
+                final ExecutionEngine descendantEngine = descendant.getExecutionEngine();
+                if (descendantEngine == ExecutionEngine.STANDARD) {
+                    throw new IllegalStateException("A Process Group using the Stateless Engine may not have a child Process Group using the Standard Engine. Cannot set Execution Engine of " + this +
+                        " to Stateless because it has a child Process Group " + descendant + " using the Standard Engine");
+                }
+            }
+        }
+
+        verifyCanUpdateExecutionEngine();
+    }
+
+    @Override
+    public void verifyCanUpdateExecutionEngine() {
+        // Ensure that no components are running / services enabled.
         for (final ProcessorNode processor : getProcessors()) {
             if (processor.isRunning()) {
                 throw new IllegalStateException("Cannot change Execution Engine for " + this + " while components are running. " + processor + " is currently running.");
@@ -4432,16 +4449,18 @@ public void verifyCanSetExecutionEngine(final ExecutionEngine executionEngine) {
             }
         }
 
+        // Ensure that there is no data queued.
         for (final Connection connection : getConnections()) {
             final boolean queueEmpty = connection.getFlowFileQueue().isEmpty();
             if (!queueEmpty) {
                 throw new IllegalStateException("Cannot change Execution Engine for " + this + " while data is queued. " + connection + " has data queued.");
             }
         }
 
+        // Ensure that all descendants are in a good state for updating the execution engine.
         for (final ProcessGroup child : getProcessGroups()) {
             if (child.getExecutionEngine() == ExecutionEngine.INHERITED) {
-                child.verifyCanSetExecutionEngine(executionEngine);
+                child.verifyCanUpdateExecutionEngine();
             }
         }
     }

nifi-framework-bundle/nifi-framework/nifi-framework-core-api/src/main/java/org/apache/nifi/groups/ProcessGroup.java

@@ -1214,6 +1214,12 @@ public interface ProcessGroup extends ComponentAuthorizable, Positionable, Versi
      */
     void verifyCanSetExecutionEngine(ExecutionEngine executionEngine);
 
+    /**
+     * Verifies that the Process Group is in a state in which the Execution Engine can be changed.
+     * @throws IllegalStateException if the Execution Engine cannot be changed at this time
+     */
+    void verifyCanUpdateExecutionEngine();
+
     /**
      * Sets the maximum number on concurrent tasks that can be run in this Process Group if using the Stateless Execution Engine
      * @param maxConcurrentTasks the maximum number of concurrent tasks

nifi-framework-bundle/nifi-framework/nifi-framework-core/src/test/java/org/apache/nifi/controller/service/mock/MockProcessGroup.java

@@ -866,6 +866,10 @@ public ExecutionEngine resolveExecutionEngine() {
     public void verifyCanSetExecutionEngine(final ExecutionEngine executionEngine) {
     }
 
+    @Override
+    public void verifyCanUpdateExecutionEngine() {
+    }
+
     @Override
     public void setMaxConcurrentTasks(final int maxConcurrentTasks) {
     }