*#Stop(): wait for own Checkable#ProcessCheckResult()s to finish

lib/checker/checkercomponent.cpp

@@ -60,6 +60,7 @@ void CheckerComponent::OnConfigLoaded()
 void CheckerComponent::Start(bool runtimeCreated)
 {
 	ObjectImpl<CheckerComponent>::Start(runtimeCreated);
+	CheckResultProducerComponent::Start();
 
 	Log(LogInformation, "CheckerComponent")
 		<< "'" << GetName() << "' started.";
@@ -81,6 +82,7 @@ void CheckerComponent::Stop(bool runtimeRemoved)
 		m_CV.notify_all();
 	}
 
+	CheckResultProducerComponent::Stop();
 	m_ResultTimer->Stop(true);
 	m_Thread.join();
 
@@ -244,7 +246,7 @@ void CheckerComponent::ExecuteCheckHelper(const Checkable::Ptr& checkable)
 		cr->SetExecutionStart(now);
 		cr->SetExecutionEnd(now);
 
-		checkable->ProcessCheckResult(cr);
+		checkable->ProcessCheckResult(cr, this);
 
 		Log(LogCritical, "checker", output);
 	}

lib/checker/checkercomponent.hpp

@@ -8,6 +8,7 @@
 #include "base/configobject.hpp"
 #include "base/timer.hpp"
 #include "base/utility.hpp"
+#include "remote/crproducer.hpp"
 #include <boost/multi_index_container.hpp>
 #include <boost/multi_index/ordered_index.hpp>
 #include <boost/multi_index/key_extractors.hpp>
@@ -46,7 +47,7 @@ struct CheckableNextCheckExtractor
 /**
  * @ingroup checker
  */
-class CheckerComponent final : public ObjectImpl<CheckerComponent>
+class CheckerComponent final : public ObjectImpl<CheckerComponent>, public CheckResultProducerComponent
 {
 public:
 	DECLARE_OBJECT(CheckerComponent);

lib/compat/externalcommandlistener.cpp

@@ -32,6 +32,7 @@ void ExternalCommandListener::StatsFunc(const Dictionary::Ptr& status, const Arr
 void ExternalCommandListener::Start(bool runtimeCreated)
 {
 	ObjectImpl<ExternalCommandListener>::Start(runtimeCreated);
+	CheckResultProducerComponent::Start();
 
 	Log(LogInformation, "ExternalCommandListener")
 		<< "'" << GetName() << "' started.";
@@ -50,6 +51,8 @@ void ExternalCommandListener::Start(bool runtimeCreated)
  */
 void ExternalCommandListener::Stop(bool runtimeRemoved)
 {
+	CheckResultProducerComponent::Stop();
+
 	Log(LogInformation, "ExternalCommandListener")
 		<< "'" << GetName() << "' stopped.";
 

lib/compat/externalcommandlistener.hpp

@@ -7,6 +7,7 @@
 #include "base/objectlock.hpp"
 #include "base/timer.hpp"
 #include "base/utility.hpp"
+#include "remote/crproducer.hpp"
 #include <thread>
 #include <iostream>
 
@@ -16,7 +17,7 @@ namespace icinga
 /**
  * @ingroup compat
  */
-class ExternalCommandListener final : public ObjectImpl<ExternalCommandListener>
+class ExternalCommandListener final : public ObjectImpl<ExternalCommandListener>, public CheckResultProducerComponent
 {
 public:
 	DECLARE_OBJECT(ExternalCommandListener);

lib/icinga/apiactions.cpp

@@ -126,7 +126,8 @@ Dictionary::Ptr ApiActions::ProcessCheckResult(const ConfigObject::Ptr& object,
 	if (params->Contains("ttl"))
 		cr->SetTtl(HttpUtility::GetLastParameter(params, "ttl"));
 
-	Result result = checkable->ProcessCheckResult(cr);
+	Result result = checkable->ProcessCheckResult(cr, ApiListener::GetInstance());
+
 	switch (result) {
 		case Result::Ok:
 			return ApiActions::CreateResult(200, "Successfully processed check result for object '" + checkable->GetName() + "'.");

lib/icinga/clusterevents.cpp

@@ -176,9 +176,9 @@ Value ClusterEvents::CheckResultAPIHandler(const MessageOrigin::Ptr& origin, con
 	}
 
 	if (!checkable->IsPaused() && Zone::GetLocalZone() == checkable->GetZone() && endpoint == checkable->GetCommandEndpoint())
-		checkable->ProcessCheckResult(cr);
+		checkable->ProcessCheckResult(cr, ApiListener::GetInstance());
 	else
-		checkable->ProcessCheckResult(cr, origin);
+		checkable->ProcessCheckResult(cr, ApiListener::GetInstance(), origin);
 
 	return Empty;
 }

lib/livestatus/livestatuslistener.cpp

@@ -47,6 +47,7 @@ void LivestatusListener::StatsFunc(const Dictionary::Ptr& status, const Array::P
 void LivestatusListener::Start(bool runtimeCreated)
 {
 	ObjectImpl<LivestatusListener>::Start(runtimeCreated);
+	CheckResultProducerComponent::Start();
 
 	Log(LogInformation, "LivestatusListener")
 		<< "'" << GetName() << "' started.";
@@ -112,6 +113,7 @@ void LivestatusListener::Stop(bool runtimeRemoved)
 		<< "'" << GetName() << "' stopped.";
 
 	m_Listener->Close();
+	CheckResultProducerComponent::Stop();
 
 	if (m_Thread.joinable())
 		m_Thread.join();

lib/livestatus/livestatuslistener.hpp

@@ -7,6 +7,7 @@
 #include "livestatus/livestatuslistener-ti.hpp"
 #include "livestatus/livestatusquery.hpp"
 #include "base/socket.hpp"
+#include "remote/crproducer.hpp"
 #include <thread>
 
 using namespace icinga;
@@ -17,7 +18,7 @@ namespace icinga
 /**
  * @ingroup livestatus
  */
-class LivestatusListener final : public ObjectImpl<LivestatusListener>
+class LivestatusListener final : public ObjectImpl<LivestatusListener>, public CheckResultProducerComponent
 {
 public:
 	DECLARE_OBJECT(LivestatusListener);

lib/remote/CMakeLists.txt

@@ -13,7 +13,7 @@ set(remote_SOURCES
   apilistener.cpp apilistener.hpp apilistener-ti.hpp apilistener-configsync.cpp apilistener-filesync.cpp
   apilistener-authority.cpp
   apiuser.cpp apiuser.hpp apiuser-ti.hpp
-  crproducer.hpp
+  crproducer.cpp crproducer.hpp
   configfileshandler.cpp configfileshandler.hpp
   configobjectslock.cpp configobjectslock.hpp
   configobjectutility.cpp configobjectutility.hpp

lib/remote/apilistener.cpp

@@ -239,6 +239,8 @@ void ApiListener::OnAllConfigLoaded()
  */
 void ApiListener::Start(bool runtimeCreated)
 {
+	CheckResultProducerComponent::Start();
+
 	Log(LogInformation, "ApiListener")
 		<< "'" << GetName() << "' started.";
 
@@ -368,6 +370,7 @@ void ApiListener::Stop(bool runtimeDeleted)
 	m_Timer->Stop(true);
 	m_RenewOwnCertTimer->Stop(true);
 
+	CheckResultProducerComponent::Stop();
 	ObjectImpl<ApiListener>::Stop(runtimeDeleted);
 
 	Log(LogInformation, "ApiListener")

lib/remote/apilistener.hpp

@@ -4,6 +4,7 @@
 #define APILISTENER_H
 
 #include "remote/apilistener-ti.hpp"
+#include "remote/crproducer.hpp"
 #include "remote/jsonrpcconnection.hpp"
 #include "remote/httpserverconnection.hpp"
 #include "remote/endpoint.hpp"
@@ -74,7 +75,7 @@ enum class ApiCapabilities : uint_fast64_t
 /**
 * @ingroup remote
 */
-class ApiListener final : public ObjectImpl<ApiListener>
+class ApiListener final : public ObjectImpl<ApiListener>, public CheckResultProducerComponent
 {
 public:
 	DECLARE_OBJECT(ApiListener);

lib/remote/crproducer.cpp

@@ -0,0 +1,92 @@
+/* Icinga 2 | (c) 2025 Icinga GmbH | GPLv2+ */
+
+#include "remote/crproducer.hpp"
+
+using namespace icinga;
+
+bool CheckResultProducerComponent::try_lock_shared() noexcept
+{
+	auto state (ModifyState(
+		[](auto current) { return current.InstanceIsActive; },
+		[](auto& desired) { ++desired.ProcessingCheckResults; }
+	));
+
+	return state.InstanceIsActive;
+}
+
+void CheckResultProducerComponent::unlock_shared() noexcept
+{
+	std::unique_lock lock (m_Mutex, std::defer_lock);
+
+	auto state (ModifyState([&lock](auto& desired) {
+		--desired.ProcessingCheckResults;
+
+		if (!desired.ProcessingCheckResults && !desired.InstanceIsActive && !lock) {
+			lock.lock();
+		}
+	}));
+
+	if (!state.ProcessingCheckResults && !state.InstanceIsActive) {
+		m_CV.notify_all();
+	}
+}
+
+/**
+ * Allow processing check results.
+ */
+void CheckResultProducerComponent::Start()
+{
+	ModifyState([](auto& desired) { desired.InstanceIsActive = 1; });
+}
+
+/**
+ * Disallow processing new check results, wait for all currently processed ones to finish.
+ */
+void CheckResultProducerComponent::Stop()
+{
+	std::unique_lock lock (m_Mutex, std::defer_lock);
+
+	auto state (ModifyState([&lock](auto& desired) {
+		desired.InstanceIsActive = 0;
+
+		if (desired.ProcessingCheckResults && !lock) {
+			lock.lock();
+		}
+	}));
+
+	if (state.ProcessingCheckResults) {
+		m_CV.wait(lock, [this] { return !m_State.load().ProcessingCheckResults; });
+	}
+}
+
+/**
+ * Load m_State into x and if cond(x), pass x to mod by reference and try to store x back.
+ * If m_State has changed in the meantime, repeat the process.
+ *
+ * @return The (not) updated m_State.
+ */
+template<class C, class M>
+inline
+CrpComponentState CheckResultProducerComponent::ModifyState(const C& cond, const M& mod)
+{
+	auto expected (m_State.load());
+	decltype(expected) desired;
+
+	do {
+		if (!cond(expected)) {
+			return expected;
+		}
+
+		desired = expected;
+		mod(desired);
+	} while (!m_State.compare_exchange_weak(expected, desired));
+
+	return desired;
+}
+
+template<class M>
+inline
+CrpComponentState CheckResultProducerComponent::ModifyState(const M& mod)
+{
+	return ModifyState([](auto) { return true; }, mod);
+}

lib/remote/crproducer.hpp

@@ -2,7 +2,11 @@
 
 #pragma once
 
+#include "base/atomic.hpp"
 #include "base/object.hpp"
+#include <condition_variable>
+#include <cstdint>
+#include <mutex>
 
 namespace icinga
 {
@@ -31,4 +35,32 @@ public:
 	virtual void unlock_shared() noexcept = 0;
 };
 
+struct CrpComponentState
+{
+	uint32_t InstanceIsActive = 0;
+	uint32_t ProcessingCheckResults = 0;
+};
+
+class CheckResultProducerComponent : public CheckResultProducer
+{
+public:
+	bool try_lock_shared() noexcept override;
+	void unlock_shared() noexcept override;
+
+protected:
+	void Start();
+	void Stop();
+
+private:
+	Atomic<CrpComponentState> m_State {CrpComponentState{}};
+	std::mutex m_Mutex;
+	std::condition_variable m_CV;
+
+	template<class C, class M>
+	CrpComponentState ModifyState(const C& cond, const M& mod);
+
+	template<class M>
+	CrpComponentState ModifyState(const M& mod);
+};
+
 }