From 289f73e4b0317231378382baede7f9fa5007ef68 Mon Sep 17 00:00:00 2001
From: Mark Payne <markap14@hotmail.com>
Date: Tue, 20 Aug 2024 10:17:48 -0400
Subject: [PATCH] NIFI-12991: 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

---
 .../nifi/groups/StandardProcessGroup.java     | 21 ++++++++++++++++++-
 .../org/apache/nifi/groups/ProcessGroup.java  |  6 ++++++
 .../service/mock/MockProcessGroup.java        |  4 ++++
 3 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/nifi-framework-bundle/nifi-framework/nifi-framework-components/src/main/java/org/apache/nifi/groups/StandardProcessGroup.java b/nifi-framework-bundle/nifi-framework/nifi-framework-components/src/main/java/org/apache/nifi/groups/StandardProcessGroup.java
index 952b2ec39634..01da985f2b43 100644
--- a/nifi-framework-bundle/nifi-framework/nifi-framework-components/src/main/java/org/apache/nifi/groups/StandardProcessGroup.java
+++ b/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.");
@@ -4432,6 +4449,7 @@ 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) {
@@ -4439,9 +4457,10 @@ public void verifyCanSetExecutionEngine(final ExecutionEngine executionEngine) {
             }
         }
 
+        // 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();
             }
         }
     }
diff --git a/nifi-framework-bundle/nifi-framework/nifi-framework-core-api/src/main/java/org/apache/nifi/groups/ProcessGroup.java b/nifi-framework-bundle/nifi-framework/nifi-framework-core-api/src/main/java/org/apache/nifi/groups/ProcessGroup.java
index a2822995bc4d..40f94f38ad14 100644
--- a/nifi-framework-bundle/nifi-framework/nifi-framework-core-api/src/main/java/org/apache/nifi/groups/ProcessGroup.java
+++ b/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
diff --git a/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/test/java/org/apache/nifi/controller/service/mock/MockProcessGroup.java b/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/test/java/org/apache/nifi/controller/service/mock/MockProcessGroup.java
index f08ec1e8734d..a7d1409935de 100644
--- a/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/test/java/org/apache/nifi/controller/service/mock/MockProcessGroup.java
+++ b/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) {
     }