MINIFICPP-2732 Clear class descriptions when extensions are cleared

Signed-off-by: Ferenc Gerlits <fgerlits@gmail.com>

Closes #2121

Author: lordgamez

libminifi/include/core/extension/ExtensionManager.h

@@ -30,6 +30,12 @@ namespace org::apache::nifi::minifi::core::extension {
 class ExtensionManager {
  public:
   explicit ExtensionManager(const std::shared_ptr<Configure>& config);
+  ~ExtensionManager();
+
+  ExtensionManager(const ExtensionManager&) = delete;
+  ExtensionManager& operator=(const ExtensionManager&) = delete;
+  ExtensionManager(ExtensionManager&&) = delete;
+  ExtensionManager& operator=(ExtensionManager&&) = delete;
 
  private:
   std::vector<std::unique_ptr<Extension>> extensions_;

libminifi/src/agent/agent_docs.cpp

@@ -34,5 +34,8 @@ std::map<BundleIdentifier, Components>& ClassDescriptionRegistry::getMutableClas
   return getAgentDocsClassMappings();
 }
 
+void ClassDescriptionRegistry::clearClassDescriptions() {
+  getAgentDocsClassMappings().clear();
+}
 
 }  // namespace org::apache::nifi::minifi

libminifi/src/core/extension/ExtensionManager.cpp

@@ -21,6 +21,7 @@
 
 #include "core/logging/LoggerConfiguration.h"
 #include "core/extension/Extension.h"
+#include "minifi-cpp/agent/agent_docs.h"
 #include "utils/file/FilePattern.h"
 #include "minifi-cpp/agent/agent_version.h"
 #include "core/extension/Utils.h"
@@ -86,4 +87,11 @@ ExtensionManager::ExtensionManager(const std::shared_ptr<Configure>& config): lo
   }
 }
 
+ExtensionManager::~ExtensionManager() {
+  // Clear the class description registry to avoid dangling pointers
+  // to validator objects that live in extension DLLs to be unloaded.
+  minifi::ClassDescriptionRegistry::clearClassDescriptions();
+  extensions_.clear();
+}
+
 }  // namespace org::apache::nifi::minifi::core::extension

minifi-api/include/minifi-cpp/agent/agent_docs.h

@@ -73,6 +73,7 @@ class ClassDescriptionRegistry {
  public:
   static const std::map<minifi::BundleIdentifier, Components>& getClassDescriptions();
   static std::map<minifi::BundleIdentifier, Components>& getMutableClassDescriptions();
+  static void clearClassDescriptions();
 
   template<typename Class, ResourceType Type>
   static void createClassDescription(std::string bundle_name, std::string class_name, std::string version);