NIFI-4436: Bug fixes; ensure correct Exception types are thrown

Signed-off-by: Matt Gilman <matt.c.gilman@gmail.com>

nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-cluster/src/main/java/org/apache/nifi/cluster/manager/ProcessGroupEntityMerger.java

@@ -48,6 +48,9 @@ public class ProcessGroupEntityMerger implements ComponentEntityMerger<ProcessGr
     private void mergeVersionControlInformation(ProcessGroupEntity targetGroup, ProcessGroupEntity toMerge) {
         final ProcessGroupDTO targetGroupDto = targetGroup.getComponent();
         final ProcessGroupDTO toMergeGroupDto = toMerge.getComponent();
+        if (targetGroupDto == null || toMergeGroupDto == null) {
+            return;
+        }
 
         final VersionControlInformationDTO targetVersionControl = targetGroupDto.getVersionControlInformation();
         final VersionControlInformationDTO toMergeVersionControl = toMergeGroupDto.getVersionControlInformation();

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

@@ -965,7 +965,7 @@ public interface ProcessGroup extends ComponentAuthorizable, Positionable, Versi
     /**
      * Disconnects this Process Group from version control. If not currently under version control, this method does nothing.
      */
-    void disconnectVersionControl();
+    void disconnectVersionControl(boolean removeVersionedComponentIds);
 
     /**
      * Synchronizes the Process Group with the given Flow Registry, determining whether or not the local flow

nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core-api/src/main/java/org/apache/nifi/registry/flow/FlowRegistry.java

@@ -212,6 +212,5 @@ public interface FlowRegistry {
      * @throws IOException if unable to communicate with the Flow Registry
      * @throws NiFiRegistryException if unable to find a flow with the given bucket ID and flow ID
      */
-    // TODO: Do we still need this?
     VersionedFlow getVersionedFlow(String bucketId, String flowId) throws IOException, NiFiRegistryException;
 }

nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/main/java/org/apache/nifi/controller/FlowController.java

@@ -234,6 +234,7 @@ import org.apache.nifi.util.ComponentIdGenerator;
 import org.apache.nifi.util.FormatUtils;
 import org.apache.nifi.util.NiFiProperties;
 import org.apache.nifi.util.ReflectionUtils;
+import org.apache.nifi.util.SnippetUtils;
 import org.apache.nifi.web.ResourceNotFoundException;
 import org.apache.nifi.web.api.dto.BatchSettingsDTO;
 import org.apache.nifi.web.api.dto.BundleDTO;
@@ -2372,26 +2373,29 @@ public class FlowController implements EventAccess, ControllerServiceProvider, R
      * </p>
      *
      * @param group group
-     * @param templateContents contents
+     * @param snippetContents contents
      */
-    private void validateSnippetContents(final ProcessGroup group, final FlowSnippetDTO templateContents) {
+    private void validateSnippetContents(final ProcessGroup group, final FlowSnippetDTO snippetContents) {
         // validate the names of Input Ports
-        for (final PortDTO port : templateContents.getInputPorts()) {
+        for (final PortDTO port : snippetContents.getInputPorts()) {
             if (group.getInputPortByName(port.getName()) != null) {
                 throw new IllegalStateException("One or more of the proposed Port names is not available in the process group");
             }
         }
 
         // validate the names of Output Ports
-        for (final PortDTO port : templateContents.getOutputPorts()) {
+        for (final PortDTO port : snippetContents.getOutputPorts()) {
             if (group.getOutputPortByName(port.getName()) != null) {
                 throw new IllegalStateException("One or more of the proposed Port names is not available in the process group");
             }
         }
 
-        verifyComponentTypesInSnippet(templateContents);
+        verifyComponentTypesInSnippet(snippetContents);
+
+        SnippetUtils.verifyNoVersionControlConflicts(snippetContents, group);
     }
 
+
     /**
      * Recursively finds all ConnectionDTO's
      *

nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/main/java/org/apache/nifi/groups/StandardProcessGroup.java

@@ -112,6 +112,7 @@ import org.apache.nifi.scheduling.ExecutionNode;
 import org.apache.nifi.scheduling.SchedulingStrategy;
 import org.apache.nifi.util.NiFiProperties;
 import org.apache.nifi.util.ReflectionUtils;
+import org.apache.nifi.util.SnippetUtils;
 import org.apache.nifi.web.Revision;
 import org.apache.nifi.web.api.dto.TemplateDTO;
 import org.slf4j.Logger;
@@ -2294,6 +2295,7 @@ public final class StandardProcessGroup implements ProcessGroup {
         try {
             verifyContents(snippet);
             verifyDestinationNotInSnippet(snippet, destination);
+            SnippetUtils.verifyNoVersionControlConflicts(snippet, this, destination);
 
             if (!isDisconnected(snippet)) {
                 throw new IllegalStateException("One or more components within the snippet is connected to a component outside of the snippet. Only a disconnected snippet may be moved.");
@@ -3087,13 +3089,15 @@ public final class StandardProcessGroup implements ProcessGroup {
     }
 
     @Override
-    public void disconnectVersionControl() {
+    public void disconnectVersionControl(final boolean removeVersionedComponentIds) {
         writeLock.lock();
         try {
             this.versionControlInfo.set(null);
 
+            if (removeVersionedComponentIds) {
                 // remove version component ids from each component (until another versioned PG is encountered)
                 applyVersionedComponentIds(this, id -> null);
+            }
         } finally {
             writeLock.unlock();
         }
@@ -3278,7 +3282,7 @@ public final class StandardProcessGroup implements ProcessGroup {
             final Set<String> knownVariables = getKnownVariableNames();
             updateProcessGroup(this, proposedSnapshot.getFlowContents(), componentIdSeed, updatedVersionedComponentIds, false, updateSettings, updateDescendantVersionedFlows, knownVariables);
         } catch (final ProcessorInstantiationException pie) {
-            throw new RuntimeException(pie);
+            throw new IllegalStateException("Failed to update flow", pie);
         } finally {
             writeLock.unlock();
         }
@@ -3366,7 +3370,9 @@ public final class StandardProcessGroup implements ProcessGroup {
         group.setVariables(updatedVariableMap);
 
         final VersionedFlowCoordinates remoteCoordinates = proposed.getVersionedFlowCoordinates();
-        if (remoteCoordinates != null) {
+        if (remoteCoordinates == null) {
+            group.disconnectVersionControl(false);
+        } else {
             final String registryId = flowController.getFlowRegistryClient().getFlowRegistryId(remoteCoordinates.getRegistryUrl());
             final String bucketId = remoteCoordinates.getBucketId();
             final String flowId = remoteCoordinates.getFlowId();
@@ -3681,8 +3687,6 @@ public final class StandardProcessGroup implements ProcessGroup {
     }
 
     private String generateUuid(final String propposedId, final String destinationGroupId, final String seed) {
-        // TODO: I think we can get rid of all of those LinkedHashSet's now in the VersionedProcessGroup because
-        /// the UUID is properly keyed off of the ID of the component in the VersionedProcessGroup.
         long msb = UUID.nameUUIDFromBytes((propposedId + destinationGroupId).getBytes(StandardCharsets.UTF_8)).getMostSignificantBits();
 
         UUID uuid;
@@ -3733,7 +3737,7 @@ public final class StandardProcessGroup implements ProcessGroup {
                 try {
                     return flowController.createPrioritizer(prioritizerName);
                 } catch (final Exception e) {
-                    throw new RuntimeException("Failed to create Prioritizer of type " + prioritizerName + " for Connection with ID " + connection.getIdentifier());
+                    throw new IllegalStateException("Failed to create Prioritizer of type " + prioritizerName + " for Connection with ID " + connection.getIdentifier());
                 }
             })
             .collect(Collectors.toList());
@@ -4016,7 +4020,14 @@ public final class StandardProcessGroup implements ProcessGroup {
                     // The value given is instead the Versioned Component ID of the Controller Service. We want to resolve this
                     // to the instance ID of the Controller Service.
                     final String serviceVersionedComponentId = entry.getValue();
-                    final String instanceId = getServiceInstanceId(serviceVersionedComponentId, group);
+                    String instanceId = getServiceInstanceId(serviceVersionedComponentId, group);
+                    if (instanceId == null) {
+                        // We didn't find the instance ID based on the Versioned Component ID. So we want to just
+                        // leave the value set to whatever it currently is, if it's currently set.
+                        final PropertyDescriptor propertyDescriptor = new PropertyDescriptor.Builder().name(entry.getKey()).build();
+                        instanceId = currentProperties.get(propertyDescriptor);
+                    }
+
                     value = instanceId == null ? serviceVersionedComponentId : instanceId;
                 } else {
                     value = entry.getValue();
@@ -4169,15 +4180,22 @@ public final class StandardProcessGroup implements ProcessGroup {
                             + " reverted to its original form before changing the version.");
                     }
                 }
+
+                verifyNoDescendantsWithLocalModifications("be updated");
             }
 
             final VersionedProcessGroup flowContents = updatedFlow.getFlowContents();
             if (verifyConnectionRemoval) {
                 // Determine which Connections have been removed.
                 final Map<String, Connection> removedConnectionByVersionedId = new HashMap<>();
+
+                // Populate the 'removedConnectionByVersionId' map with all Connections. We key off of the connection's VersionedComponentID
+                // if it is populated. Otherwise, we key off of its actual ID. We do this because it allows us to then remove from this Map
+                // any connection that does exist in the proposed flow. This results in us having a Map whose values are those Connections
+                // that were removed. We can then check for any connections that have data in them. If any Connection is to be removed but
+                // has data, then we should throw an IllegalStateException.
                 findAllConnections().stream()
-                    .filter(conn -> conn.getVersionedComponentId().isPresent())
+                    .forEach(conn -> removedConnectionByVersionedId.put(conn.getVersionedComponentId().orElse(conn.getIdentifier()), conn));
-                    .forEach(conn -> removedConnectionByVersionedId.put(conn.getVersionedComponentId().get(), conn));
 
                 final Set<String> proposedFlowConnectionIds = new HashSet<>();
                 findAllConnectionIds(flowContents, proposedFlowConnectionIds);
@@ -4252,8 +4270,8 @@ public final class StandardProcessGroup implements ProcessGroup {
                 if (!proposedProcessGroups.containsKey(versionedId)) {
                     // Process Group was removed.
                     throw new IllegalStateException(this + " cannot be updated to the proposed version of the flow because the child " + childGroup
-                        + " that exists locally has one or more Templates, and the proposed flow does not contain this Process Group. "
+                        + " that exists locally has one or more Templates, and the proposed flow does not contain these templates. "
-                        + "A Process Group cannot be deleted while it contains Templates. Please remove the Templates before attempting to chnage the version of the flow.");
+                        + "A Process Group cannot be deleted while it contains Templates. Please remove the Templates before attempting to change the version of the flow.");
                 }
             }
 
@@ -4430,6 +4448,12 @@ public final class StandardProcessGroup implements ProcessGroup {
                         + "has local modifications. Each descendant Process Group that is under Version Control must first be reverted or have its changes pushed to the Flow Registry before "
                         + "this action can be performed on the parent Process Group.");
                 }
+
+                if (flowState == VersionedFlowState.SYNC_FAILURE) {
+                    throw new IllegalStateException("Process Group cannot " + action + " because it contains a child or descendant Process Group that is under Version Control and "
+                        + "is not synchronized with the Flow Registry. Each descendant Process Group must first be synchronized with the Flow Registry before this action can be "
+                        + "performed on the parent Process Group. NiFi will continue to attempt to communicate with the Flow Registry periodically in the background.");
+                }
             }
         }
     }

nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/main/java/org/apache/nifi/registry/flow/StandardFlowRegistryClient.java

@@ -43,6 +43,13 @@ public class StandardFlowRegistryClient implements FlowRegistryClient {
 
     @Override
     public void addFlowRegistry(final FlowRegistry registry) {
+        final boolean duplicateName = registryById.values().stream()
+            .anyMatch(reg -> reg.getName().equals(registry.getName()));
+
+        if (duplicateName) {
+            throw new IllegalStateException("Cannot add Flow Registry because a Flow Registry already exists with the name " + registry.getName());
+        }
+
         final FlowRegistry existing = registryById.putIfAbsent(registry.getIdentifier(), registry);
         if (existing != null) {
             throw new IllegalStateException("Cannot add Flow Registry " + registry + " because a Flow Registry already exists with the ID " + registry.getIdentifier());
@@ -58,7 +65,7 @@ public class StandardFlowRegistryClient implements FlowRegistryClient {
         if (uriScheme.equalsIgnoreCase("http") || uriScheme.equalsIgnoreCase("https")) {
             final SSLContext sslContext = SslContextFactory.createSslContext(nifiProperties, false);
             if (sslContext == null && uriScheme.equalsIgnoreCase("https")) {
-                throw new RuntimeException("Failed to create Flow Registry for URI " + registryUrl
+                throw new IllegalStateException("Failed to create Flow Registry for URI " + registryUrl
                     + " because this NiFi is not configured with a Keystore/Truststore, so it is not capable of communicating with a secure Registry. "
                     + "Please populate NiFi's Keystore/Truststore properties or connect to a NiFi Registry over http instead of https.");
             }
@@ -68,7 +75,7 @@ public class StandardFlowRegistryClient implements FlowRegistryClient {
         } else if (uriScheme.equalsIgnoreCase("http") || uriScheme.equalsIgnoreCase("https")) {
             final SSLContext sslContext = SslContextFactory.createSslContext(nifiProperties, false);
             if (sslContext == null && uriScheme.equalsIgnoreCase("https")) {
-                throw new RuntimeException("Failed to create Flow Registry for URI " + registryUrl
+                throw new IllegalStateException("Failed to create Flow Registry for URI " + registryUrl
                     + " because this NiFi is not configured with a Keystore/Truststore, so it is not capable of communicating with a secure Registry. "
                     + "Please populate NiFi's Keystore/Truststore properties or connect to a NiFi Registry over http instead of https.");
             }

nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/main/java/org/apache/nifi/util/SnippetUtils.java

@@ -16,11 +16,15 @@
  */
 package org.apache.nifi.util;
 
+import org.apache.nifi.controller.Snippet;
+import org.apache.nifi.groups.ProcessGroup;
+import org.apache.nifi.registry.flow.VersionControlInformation;
 import org.apache.nifi.web.api.dto.ComponentDTO;
 import org.apache.nifi.web.api.dto.ConnectionDTO;
 import org.apache.nifi.web.api.dto.FlowSnippetDTO;
 import org.apache.nifi.web.api.dto.PositionDTO;
 import org.apache.nifi.web.api.dto.ProcessGroupDTO;
+import org.apache.nifi.web.api.dto.VersionControlInformationDTO;
 
 import java.util.ArrayList;
 import java.util.Collection;
@@ -307,4 +311,99 @@ public final class SnippetUtils {
             connection.setBends(bends);
         }
     }
+
+    public static void verifyNoVersionControlConflicts(final Snippet snippet, final ProcessGroup parentGroup, final ProcessGroup destination) {
+        if (snippet == null) {
+            return;
+        }
+        if (snippet.getProcessGroups() == null) {
+            return;
+        }
+
+        final List<VersionControlInformation> vcis = new ArrayList<>();
+        for (final String groupId : snippet.getProcessGroups().keySet()) {
+            final ProcessGroup group = parentGroup.getProcessGroup(groupId);
+            if (group != null) {
+                findAllVersionControlInfo(group, vcis);
+            }
+        }
+
+        verifyNoDuplicateVersionControlInfo(destination, vcis);
+    }
+
+    public static void verifyNoVersionControlConflicts(final FlowSnippetDTO snippetContents, final ProcessGroup destination) {
+        final List<VersionControlInformationDTO> vcis = new ArrayList<>();
+        for (final ProcessGroupDTO childGroup : snippetContents.getProcessGroups()) {
+            findAllVersionControlInfo(childGroup, vcis);
+        }
+
+        verifyNoDuplicateVersionControlInfoDtos(destination, vcis);
+    }
+
+    private static void verifyNoDuplicateVersionControlInfoDtos(final ProcessGroup group, final Collection<VersionControlInformationDTO> snippetVcis) {
+        final VersionControlInformation vci = group.getVersionControlInformation();
+        if (vci != null) {
+            for (final VersionControlInformationDTO snippetVci : snippetVcis) {
+                if (vci.getBucketIdentifier().equals(snippetVci.getBucketId()) && vci.getFlowIdentifier().equals(snippetVci.getFlowId())) {
+                    throw new IllegalArgumentException("Cannot place the given Process Group into the desired destination because the destination group or one of its ancestor groups is "
+                        + "under Version Control and one of the selected Process Groups is also under Version Control with the same Flow. A Process Group that is under Version Control "
+                        + "cannot contain a child Process Group that points to the same Versioned Flow.");
+                }
+            }
+        }
+
+        final ProcessGroup parent = group.getParent();
+        if (parent != null) {
+            verifyNoDuplicateVersionControlInfoDtos(parent, snippetVcis);
+        }
+    }
+
+    private static void verifyNoDuplicateVersionControlInfo(final ProcessGroup group, final Collection<VersionControlInformation> snippetVcis) {
+        final VersionControlInformation vci = group.getVersionControlInformation();
+        if (vci != null) {
+            for (final VersionControlInformation snippetVci : snippetVcis) {
+                if (vci.getBucketIdentifier().equals(snippetVci.getBucketIdentifier()) && vci.getFlowIdentifier().equals(snippetVci.getFlowIdentifier())) {
+                    throw new IllegalArgumentException("Cannot place the given Process Group into the desired destination because the destination group or one of its ancestor groups is "
+                        + "under Version Control and one of the selected Process Groups is also under Version Control with the same Flow. A Process Group that is under Version Control "
+                        + "cannot contain a child Process Group that points to the same Versioned Flow.");
+                }
+            }
+        }
+
+        final ProcessGroup parent = group.getParent();
+        if (parent != null) {
+            verifyNoDuplicateVersionControlInfo(parent, snippetVcis);
+        }
+    }
+
+
+    private static void findAllVersionControlInfo(final ProcessGroupDTO dto, final List<VersionControlInformationDTO> found) {
+        final VersionControlInformationDTO vci = dto.getVersionControlInformation();
+        if (vci != null) {
+            found.add(vci);
+        }
+
+        final FlowSnippetDTO contents = dto.getContents();
+        if (contents != null) {
+            for (final ProcessGroupDTO child : contents.getProcessGroups()) {
+                findAllVersionControlInfo(child, found);
+            }
+        }
+    }
+
+    private static void findAllVersionControlInfo(final ProcessGroup group, final List<VersionControlInformation> found) {
+        if (group == null) {
+            return;
+        }
+
+        final VersionControlInformation vci = group.getVersionControlInformation();
+        if (vci != null) {
+            found.add(vci);
+        }
+
+        for (final ProcessGroup childGroup : group.findAllProcessGroups()) {
+            findAllVersionControlInfo(childGroup, found);
+        }
+    }
+
 }

nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/test/groovy/org/apache/nifi/controller/StandardFlowSynchronizerSpec.groovy

@@ -127,6 +127,8 @@ class StandardFlowSynchronizerSpec extends Specification {
                     }
                 }
             }
+			_ * processGroup.findAllRemoteProcessGroups() >> []
+            
             positionableMocksById.put(pgId, processGroup)
             return processGroup
         }

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

@@ -667,7 +667,7 @@ public class MockProcessGroup implements ProcessGroup {
     }
 
     @Override
-    public void disconnectVersionControl() {
+    public void disconnectVersionControl(final boolean removeVersionedComponentIds) {
         this.versionControlInfo = null;
     }
 

nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-web/nifi-web-api/src/main/java/org/apache/nifi/web/NiFiServiceFacade.java

@@ -23,7 +23,6 @@ import org.apache.nifi.controller.ScheduledState;
 import org.apache.nifi.controller.repository.claim.ContentDirection;
 import org.apache.nifi.controller.service.ControllerServiceState;
 import org.apache.nifi.groups.ProcessGroup;
-import org.apache.nifi.registry.client.NiFiRegistryException;
 import org.apache.nifi.registry.flow.VersionedFlow;
 import org.apache.nifi.registry.flow.VersionedFlowSnapshot;
 import org.apache.nifi.registry.flow.VersionedProcessGroup;
@@ -117,7 +116,6 @@ import org.apache.nifi.web.api.entity.VersionControlInformationEntity;
 import org.apache.nifi.web.api.entity.VersionedFlowEntity;
 import org.apache.nifi.web.api.entity.VersionedFlowSnapshotMetadataEntity;
 
-import java.io.IOException;
 import java.util.Date;
 import java.util.List;
 import java.util.Map;
@@ -423,11 +421,12 @@ public interface NiFiServiceFacade {
      * with the given id
      *
      * @param versionControlInfo the information about the versioned flow
+     * @param versionedProcessGroup the contents to be imported
      * @param groupId the ID of the Process Group where the flow should be instantiated
      *
      * @throws IllegalStateException if the flow cannot be imported into the specified group
      */
-    void verifyImportProcessGroup(VersionControlInformationDTO versionControlInfo, String groupId);
+    void verifyImportProcessGroup(VersionControlInformationDTO versionControlInfo, final VersionedProcessGroup versionedProcessGroup, String groupId);
 
     /**
      * Creates a new Template based off the specified snippet.
@@ -1295,7 +1294,7 @@ public interface NiFiServiceFacade {
      *         was last synchronized with the Flow Registry
      * @throws IllegalStateException if the Process Group with the given ID is not under version control
      */
-    FlowComparisonEntity getLocalModifications(String processGroupId) throws IOException, NiFiRegistryException;
+    FlowComparisonEntity getLocalModifications(String processGroupId);
 
     /**
      * Returns the Version Control information for the Process Group with the given ID
@@ -1314,9 +1313,9 @@ public interface NiFiServiceFacade {
      * @param flow the flow to add to the registry
      * @return a VersionedFlow that is fully populated, including identifiers
      *
-     * @throws IOException if unable to communicate with the Flow Registry
+     * @throws NiFiCoreException if unable to register flow
      */
-    VersionedFlow registerVersionedFlow(String registryId, VersionedFlow flow) throws IOException, NiFiRegistryException;
+    VersionedFlow registerVersionedFlow(String registryId, VersionedFlow flow);
 
     /**
      * Creates a snapshot of the Process Group with the given identifier, then creates a new Flow entity in the NiFi Registry
@@ -1337,7 +1336,7 @@ public interface NiFiServiceFacade {
      * @param flowId the ID of the flow
      * @return the VersionedFlow that was deleted
      */
-    VersionedFlow deleteVersionedFlow(String registryId, String bucketId, String flowId) throws IOException, NiFiRegistryException;
+    VersionedFlow deleteVersionedFlow(String registryId, String bucketId, String flowId);
 
     /**
      * Adds the given snapshot to the already existing Versioned Flow, which resides in the given Flow Registry with the given id
@@ -1349,10 +1348,9 @@ public interface NiFiServiceFacade {
      * @param expectedVersion the version to save the flow as
      * @return the snapshot that represents what was stored in the registry
      *
-     * @throws IOException if unable to communicate with the Flow Registry
+     * @throws NiFiCoreException if unable to register the snapshot with the flow registry
      */
-    VersionedFlowSnapshot registerVersionedFlowSnapshot(String registryId, VersionedFlow flow, VersionedProcessGroup snapshot, String comments, int expectedVersion)
+    VersionedFlowSnapshot registerVersionedFlowSnapshot(String registryId, VersionedFlow flow, VersionedProcessGroup snapshot, String comments, int expectedVersion);
-        throws IOException, NiFiRegistryException;
 
     /**
      * Updates the Version Control Information on the Process Group with the given ID
@@ -1386,7 +1384,7 @@ public interface NiFiServiceFacade {
      *
      * @throws ResourceNotFoundException if the Versioned Flow Snapshot could not be found
      */
-    VersionedFlowSnapshot getVersionedFlowSnapshot(VersionControlInformationDTO versionControlInfo, boolean fetchRemoteFlows) throws IOException;
+    VersionedFlowSnapshot getVersionedFlowSnapshot(VersionControlInformationDTO versionControlInfo, boolean fetchRemoteFlows);
 
     /**
      * Returns the name of the Flow Registry that is registered with the given ID. If no Flow Registry exists with the given ID, will return
@@ -1406,7 +1404,7 @@ public interface NiFiServiceFacade {
      * @param user the user making the request
      * @return the set of all components that would be affected by updating the Process Group
      */
-    Set<AffectedComponentEntity> getComponentsAffectedByVersionChange(String processGroupId, VersionedFlowSnapshot updatedSnapshot, NiFiUser user) throws IOException;
+    Set<AffectedComponentEntity> getComponentsAffectedByVersionChange(String processGroupId, VersionedFlowSnapshot updatedSnapshot, NiFiUser user);
 
     /**
      * Verifies that the Process Group with the given identifier can be updated to the proposed flow

nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-web/nifi-web-api/src/main/java/org/apache/nifi/web/StandardNiFiServiceFacade.java

@@ -95,6 +95,7 @@ import org.apache.nifi.registry.flow.VersionControlInformation;
 import org.apache.nifi.registry.flow.VersionedComponent;
 import org.apache.nifi.registry.flow.VersionedConnection;
 import org.apache.nifi.registry.flow.VersionedFlow;
+import org.apache.nifi.registry.flow.VersionedFlowCoordinates;
 import org.apache.nifi.registry.flow.VersionedFlowSnapshot;
 import org.apache.nifi.registry.flow.VersionedFlowSnapshotMetadata;
 import org.apache.nifi.registry.flow.VersionedFlowState;
@@ -1866,20 +1867,21 @@ public class StandardNiFiServiceFacade implements NiFiServiceFacade {
     }
 
     @Override
-    public void verifyImportProcessGroup(final VersionControlInformationDTO versionControlInfo, final String groupId) {
+    public void verifyImportProcessGroup(final VersionControlInformationDTO versionControlInfo, final VersionedProcessGroup contents, final String groupId) {
         final ProcessGroup group = processGroupDAO.getProcessGroup(groupId);
-        verifyImportProcessGroup(versionControlInfo, group);
+        verifyImportProcessGroup(versionControlInfo, contents, group);
     }
 
-    private void verifyImportProcessGroup(final VersionControlInformationDTO vciDto, final ProcessGroup group) {
+    private void verifyImportProcessGroup(final VersionControlInformationDTO vciDto, final VersionedProcessGroup contents, final ProcessGroup group) {
         if (group == null) {
             return;
         }
 
         final VersionControlInformation vci = group.getVersionControlInformation();
         if (vci != null) {
-            if (Objects.equals(vciDto.getRegistryId(), vci.getRegistryIdentifier())
+            // Note that we do not compare the Registry ID here because there could be two registry clients
-                && Objects.equals(vciDto.getBucketId(), vci.getBucketIdentifier())
+            // that point to the same server (one could point to localhost while another points to 127.0.0.1, for instance)..
+            if (Objects.equals(vciDto.getBucketId(), vci.getBucketIdentifier())
                 && Objects.equals(vciDto.getFlowId(), vci.getFlowIdentifier())) {
 
                 throw new IllegalStateException("Cannot import the specified Versioned Flow into the Process Group because doing so would cause a recursive dataflow. "
@@ -1887,7 +1889,20 @@ public class StandardNiFiServiceFacade implements NiFiServiceFacade {
             }
         }
 
-        verifyImportProcessGroup(vciDto, group.getParent());
+        final Set<VersionedProcessGroup> childGroups = contents.getProcessGroups();
+        if (childGroups != null) {
+            for (final VersionedProcessGroup childGroup : childGroups) {
+                final VersionedFlowCoordinates childCoordinates = childGroup.getVersionedFlowCoordinates();
+                if (childCoordinates != null) {
+                    final VersionControlInformationDTO childVci = new VersionControlInformationDTO();
+                    childVci.setBucketId(childCoordinates.getBucketId());
+                    childVci.setFlowId(childCoordinates.getFlowId());
+                    verifyImportProcessGroup(childVci, childGroup, group);
+                }
+            }
+        }
+
+        verifyImportProcessGroup(vciDto, contents, group.getParent());
     }
 
     @Override
@@ -3447,8 +3462,6 @@ public class StandardNiFiServiceFacade implements NiFiServiceFacade {
         entity.setPoliciesPermissions(dtoFactory.createPermissionsDto(authorizableLookup.getPolicies()));
         entity.setSystemPermissions(dtoFactory.createPermissionsDto(authorizableLookup.getSystem()));
         entity.setRestrictedComponentsPermissions(dtoFactory.createPermissionsDto(authorizableLookup.getRestrictedComponents()));
-
-        // TODO - update to be user specific
         entity.setCanVersionFlows(CollectionUtils.isNotEmpty(flowRegistryClient.getRegistryIdentifiers()));
 
         return entity;
@@ -3722,13 +3735,17 @@ public class StandardNiFiServiceFacade implements NiFiServiceFacade {
     }
 
     @Override
-    public VersionedFlow deleteVersionedFlow(final String registryId, final String bucketId, final String flowId) throws IOException, NiFiRegistryException {
+    public VersionedFlow deleteVersionedFlow(final String registryId, final String bucketId, final String flowId) {
         final FlowRegistry registry = flowRegistryClient.getFlowRegistry(registryId);
         if (registry == null) {
             throw new IllegalArgumentException("No Flow Registry exists with ID " + registryId);
         }
 
+        try {
             return registry.deleteVersionedFlow(bucketId, flowId, NiFiUserUtils.getNiFiUser());
+        } catch (final IOException | NiFiRegistryException e) {
+            throw new NiFiCoreException("Failed to remove flow from Flow Registry due to " + e.getMessage(), e);
+        }
     }
 
     @Override
@@ -3752,7 +3769,7 @@ public class StandardNiFiServiceFacade implements NiFiServiceFacade {
     }
 
     @Override
-    public FlowComparisonEntity getLocalModifications(final String processGroupId) throws IOException, NiFiRegistryException {
+    public FlowComparisonEntity getLocalModifications(final String processGroupId) {
         final ProcessGroup processGroup = processGroupDAO.getProcessGroup(processGroupId);
         final VersionControlInformation versionControlInfo = processGroup.getVersionControlInformation();
         if (versionControlInfo == null) {
@@ -3765,11 +3782,16 @@ public class StandardNiFiServiceFacade implements NiFiServiceFacade {
                 + " but cannot find a Flow Registry with that identifier");
         }
 
-        final VersionedFlowSnapshot versionedFlowSnapshot = flowRegistry.getFlowContents(versionControlInfo.getBucketIdentifier(),
+        final VersionedFlowSnapshot versionedFlowSnapshot;
-            versionControlInfo.getFlowIdentifier(), versionControlInfo.getVersion(), false, NiFiUserUtils.getNiFiUser());
+        try {
+            versionedFlowSnapshot = flowRegistry.getFlowContents(versionControlInfo.getBucketIdentifier(),
+                versionControlInfo.getFlowIdentifier(), versionControlInfo.getVersion(), true, NiFiUserUtils.getNiFiUser());
+        } catch (final IOException | NiFiRegistryException e) {
+            throw new NiFiCoreException("Failed to retrieve flow with Flow Registry in order to calculate local differences due to " + e.getMessage(), e);
+        }
 
         final NiFiRegistryFlowMapper mapper = new NiFiRegistryFlowMapper();
-        final VersionedProcessGroup localGroup = mapper.mapProcessGroup(processGroup, controllerFacade.getControllerServiceProvider(), flowRegistryClient, false);
+        final VersionedProcessGroup localGroup = mapper.mapProcessGroup(processGroup, controllerFacade.getControllerServiceProvider(), flowRegistryClient, true);
         final VersionedProcessGroup registryGroup = versionedFlowSnapshot.getFlowContents();
 
         final ComparableDataFlow localFlow = new StandardComparableDataFlow("Local Flow", localGroup);
@@ -3802,13 +3824,17 @@ public class StandardNiFiServiceFacade implements NiFiServiceFacade {
     }
 
     @Override
-    public VersionedFlow registerVersionedFlow(final String registryId, final VersionedFlow flow) throws IOException, NiFiRegistryException {
+    public VersionedFlow registerVersionedFlow(final String registryId, final VersionedFlow flow) {
         final FlowRegistry registry = flowRegistryClient.getFlowRegistry(registryId);
         if (registry == null) {
             throw new ResourceNotFoundException("No Flow Registry exists with ID " + registryId);
         }
 
+        try {
             return registry.registerVersionedFlow(flow, NiFiUserUtils.getNiFiUser());
+        } catch (final IOException | NiFiRegistryException e) {
+            throw new NiFiCoreException("Failed to register flow with Flow Registry due to " + e.getMessage(), e);
+        }
     }
 
     private VersionedFlow getVersionedFlow(final String registryId, final String bucketId, final String flowId) throws IOException, NiFiRegistryException {
@@ -3822,13 +3848,17 @@ public class StandardNiFiServiceFacade implements NiFiServiceFacade {
 
     @Override
     public VersionedFlowSnapshot registerVersionedFlowSnapshot(final String registryId, final VersionedFlow flow,
-        final VersionedProcessGroup snapshot, final String comments, final int expectedVersion) throws IOException, NiFiRegistryException {
+        final VersionedProcessGroup snapshot, final String comments, final int expectedVersion) {
         final FlowRegistry registry = flowRegistryClient.getFlowRegistry(registryId);
         if (registry == null) {
             throw new ResourceNotFoundException("No Flow Registry exists with ID " + registryId);
         }
 
+        try {
             return registry.registerVersionedFlowSnapshot(flow, snapshot, comments, expectedVersion, NiFiUserUtils.getNiFiUser());
+        } catch (final IOException | NiFiRegistryException e) {
+            throw new NiFiCoreException("Failed to register flow with Flow Registry due to " + e.getMessage(), e);
+        }
     }
 
     @Override
@@ -3881,7 +3911,7 @@ public class StandardNiFiServiceFacade implements NiFiServiceFacade {
     }
 
     @Override
-    public Set<AffectedComponentEntity> getComponentsAffectedByVersionChange(final String processGroupId, final VersionedFlowSnapshot updatedSnapshot, final NiFiUser user) throws IOException {
+    public Set<AffectedComponentEntity> getComponentsAffectedByVersionChange(final String processGroupId, final VersionedFlowSnapshot updatedSnapshot, final NiFiUser user) {
         final ProcessGroup group = processGroupDAO.getProcessGroup(processGroupId);
 
         final NiFiRegistryFlowMapper mapper = new NiFiRegistryFlowMapper();
@@ -4057,7 +4087,7 @@ public class StandardNiFiServiceFacade implements NiFiServiceFacade {
     }
 
     @Override
-    public VersionedFlowSnapshot getVersionedFlowSnapshot(final VersionControlInformationDTO versionControlInfo, final boolean fetchRemoteFlows) throws IOException {
+    public VersionedFlowSnapshot getVersionedFlowSnapshot(final VersionControlInformationDTO versionControlInfo, final boolean fetchRemoteFlows) {
         final FlowRegistry flowRegistry = flowRegistryClient.getFlowRegistry(versionControlInfo.getRegistryId());
         if (flowRegistry == null) {
             throw new ResourceNotFoundException("Could not find any Flow Registry registered with identifier " + versionControlInfo.getRegistryId());
@@ -4066,7 +4096,7 @@ public class StandardNiFiServiceFacade implements NiFiServiceFacade {
         final VersionedFlowSnapshot snapshot;
         try {
             snapshot = flowRegistry.getFlowContents(versionControlInfo.getBucketId(), versionControlInfo.getFlowId(), versionControlInfo.getVersion(), fetchRemoteFlows, NiFiUserUtils.getNiFiUser());
-        } catch (final NiFiRegistryException e) {
+        } catch (final NiFiRegistryException | IOException e) {
             throw new IllegalArgumentException("The Flow Registry with ID " + versionControlInfo.getRegistryId() + " reports that no Flow exists with Bucket "
                 + versionControlInfo.getBucketId() + ", Flow " + versionControlInfo.getFlowId() + ", Version " + versionControlInfo.getVersion());
         }

nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-web/nifi-web-api/src/main/java/org/apache/nifi/web/api/ProcessGroupResource.java

@@ -1644,10 +1644,6 @@ public class ProcessGroupResource extends ApplicationResource {
         // Step 6: Replicate the request or call serviceFacade.updateProcessGroup
 
         final VersionControlInformationDTO versionControlInfo = requestProcessGroupEntity.getComponent().getVersionControlInformation();
-        if (versionControlInfo != null) {
-            serviceFacade.verifyImportProcessGroup(versionControlInfo, groupId);
-        }
-
         if (versionControlInfo != null && requestProcessGroupEntity.getVersionedFlowSnapshot() == null) {
             // Step 1: Ensure that user has write permissions to the Process Group. If not, then immediately fail.
             // Step 2: Retrieve flow from Flow Registry
@@ -1670,6 +1666,11 @@ public class ProcessGroupResource extends ApplicationResource {
             requestProcessGroupEntity.setVersionedFlowSnapshot(flowSnapshot);
         }
 
+        if (versionControlInfo != null) {
+            final VersionedFlowSnapshot flowSnapshot = requestProcessGroupEntity.getVersionedFlowSnapshot();
+            serviceFacade.verifyImportProcessGroup(versionControlInfo, flowSnapshot.getFlowContents(), groupId);
+        }
+
         // Step 6: Replicate the request or call serviceFacade.updateProcessGroup
         if (isReplicateRequest()) {
             return replicate(HttpMethod.POST, requestProcessGroupEntity);

nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-web/nifi-web-api/src/main/java/org/apache/nifi/web/api/VersionsResource.java

@@ -1110,7 +1110,7 @@ public class VersionsResource extends ApplicationResource {
                 // Create an asynchronous request that will occur in the background, because this request may
                 // result in stopping components, which can take an indeterminate amount of time.
                 final String requestId = UUID.randomUUID().toString();
-                final AsynchronousWebRequest<VersionControlInformationEntity> request = new StandardAsynchronousWebRequest<>(requestId, groupId, user, "Stopping Processors");
+                final AsynchronousWebRequest<VersionControlInformationEntity> request = new StandardAsynchronousWebRequest<>(requestId, groupId, user, "Stopping Affected Processors");
 
                 // Submit the request to be performed in the background
                 final Consumer<AsynchronousWebRequest<VersionControlInformationEntity>> updateTask = vcur -> {
@@ -1275,7 +1275,7 @@ public class VersionsResource extends ApplicationResource {
                 // Create an asynchronous request that will occur in the background, because this request may
                 // result in stopping components, which can take an indeterminate amount of time.
                 final String requestId = UUID.randomUUID().toString();
-                final AsynchronousWebRequest<VersionControlInformationEntity> request = new StandardAsynchronousWebRequest<>(requestId, groupId, user, "Stopping Processors");
+                final AsynchronousWebRequest<VersionControlInformationEntity> request = new StandardAsynchronousWebRequest<>(requestId, groupId, user, "Stopping Affected Processors");
 
                 // Submit the request to be performed in the background
                 final Consumer<AsynchronousWebRequest<VersionControlInformationEntity>> updateTask = vcur -> {

nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-web/nifi-web-api/src/main/java/org/apache/nifi/web/dao/impl/StandardControllerServiceDAO.java

@@ -172,12 +172,13 @@ public class StandardControllerServiceDAO extends ComponentDAO implements Contro
             }
         }
 
-        controllerService.getProcessGroup().onComponentModified();
+        final ProcessGroup group = controllerService.getProcessGroup();
+        if (group != null) {
+            group.onComponentModified();
 
             // For any component that references this Controller Service, find the component's Process Group
             // and notify the Process Group that a component has been modified. This way, we know to re-calculate
             // whether or not the Process Group has local modifications.
-        final ProcessGroup group = controllerService.getProcessGroup();
             controllerService.getReferences().getReferencingComponents().stream()
                 .map(ConfiguredComponent::getProcessGroupIdentifier)
                 .filter(id -> !id.equals(group.getIdentifier()))
@@ -187,6 +188,7 @@ public class StandardControllerServiceDAO extends ComponentDAO implements Contro
                         descendant.onComponentModified();
                     }
                 });
+        }
 
         return controllerService;
     }

nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-web/nifi-web-api/src/main/java/org/apache/nifi/web/dao/impl/StandardProcessGroupDAO.java

@@ -274,7 +274,7 @@ public class StandardProcessGroupDAO extends ComponentDAO implements ProcessGrou
     @Override
     public ProcessGroup disconnectVersionControl(final String groupId) {
         final ProcessGroup group = locateProcessGroup(flowController, groupId);
-        group.disconnectVersionControl();
+        group.disconnectVersionControl(true);
         return group;
     }
 

nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-web/nifi-web-api/src/main/java/org/apache/nifi/web/util/SnippetUtils.java

@@ -90,7 +90,6 @@ public final class SnippetUtils {
     private DtoFactory dtoFactory;
     private AccessPolicyDAO accessPolicyDAO;
 
-
     /**
      * Populates the specified snippet and returns the details.
      *