From e3a7ee079a0a65e824e9752a20b35bb9f6be9d95 Mon Sep 17 00:00:00 2001
From: Yonas Habteab <yonas.habteab@icinga.com>
Date: Fri, 8 Mar 2024 09:58:32 +0100
Subject: [PATCH] Introduce RAII style `ObjectNameLock` class

---
 lib/remote/CMakeLists.txt        |  1 +
 lib/remote/configobjectslock.cpp | 39 ++++++++++++++++++++++++++++++++
 lib/remote/configobjectslock.hpp | 39 ++++++++++++++++++++++++++++++++
 3 files changed, 79 insertions(+)
 create mode 100644 lib/remote/configobjectslock.cpp
 create mode 100644 lib/remote/configobjectslock.hpp

diff --git a/lib/remote/CMakeLists.txt b/lib/remote/CMakeLists.txt
index 2c5a0326a..740b112b4 100644
--- a/lib/remote/CMakeLists.txt
+++ b/lib/remote/CMakeLists.txt
@@ -14,6 +14,7 @@ set(remote_SOURCES
   apilistener-authority.cpp
   apiuser.cpp apiuser.hpp apiuser-ti.hpp
   configfileshandler.cpp configfileshandler.hpp
+  configobjectslock.cpp configobjectslock.hpp
   configobjectutility.cpp configobjectutility.hpp
   configpackageshandler.cpp configpackageshandler.hpp
   configpackageutility.cpp configpackageutility.hpp
diff --git a/lib/remote/configobjectslock.cpp b/lib/remote/configobjectslock.cpp
new file mode 100644
index 000000000..ba59a0db3
--- /dev/null
+++ b/lib/remote/configobjectslock.cpp
@@ -0,0 +1,39 @@
+/* Icinga 2 | (c) 2022 Icinga GmbH | GPLv2+ */
+
+#include "remote/configobjectslock.hpp"
+
+using namespace icinga;
+
+std::mutex ObjectNameLock::m_Mutex;
+std::condition_variable ObjectNameLock::m_CV;
+std::map<Type*, std::set<String>> ObjectNameLock::m_LockedObjectNames;
+
+/**
+ * Locks the specified object name of the given type and unlocks it upon destruction of the instance of this class.
+ *
+ * If it is already locked, the call blocks until the lock is released.
+ *
+ * @param Type::Ptr ptype The type of the object you want to lock
+ * @param String objName The object name you want to lock
+ */
+ObjectNameLock::ObjectNameLock(const Type::Ptr& ptype, const String& objName): m_ObjectName{objName}, m_Type{ptype}
+{
+	std::unique_lock<std::mutex> lock(m_Mutex);
+	m_CV.wait(lock, [this]{
+		auto& locked = m_LockedObjectNames[m_Type.get()];
+		return locked.find(m_ObjectName) == locked.end();
+	});
+
+	// Add the object name to the locked list to block all other threads that try
+	// to process a message affecting the same object.
+	m_LockedObjectNames[ptype.get()].emplace(objName);
+}
+
+ObjectNameLock::~ObjectNameLock()
+{
+	{
+		std::unique_lock<std::mutex> lock(m_Mutex);
+		m_LockedObjectNames[m_Type.get()].erase(m_ObjectName);
+	}
+	m_CV.notify_all();
+}
diff --git a/lib/remote/configobjectslock.hpp b/lib/remote/configobjectslock.hpp
new file mode 100644
index 000000000..5add769d2
--- /dev/null
+++ b/lib/remote/configobjectslock.hpp
@@ -0,0 +1,39 @@
+/* Icinga 2 | (c) 2023 Icinga GmbH | GPLv2+ */
+
+#pragma once
+
+#include "base/type.hpp"
+#include "base/string.hpp"
+#include <condition_variable>
+#include <map>
+#include <mutex>
+#include <set>
+
+namespace icinga
+{
+
+/**
+ * Allows you to easily lock/unlock a specific object of a given type by its name.
+ *
+ * That way, locking an object "this" of type Host does not affect an object "this" of
+ * type "Service" nor an object "other" of type "Host".
+ *
+ * @ingroup remote
+ */
+class ObjectNameLock
+{
+public:
+	ObjectNameLock(const Type::Ptr& ptype, const String& objName);
+
+	~ObjectNameLock();
+
+private:
+	String m_ObjectName;
+	Type::Ptr m_Type;
+
+	static std::mutex m_Mutex;
+	static std::condition_variable m_CV;
+	static std::map<Type*, std::set<String>> m_LockedObjectNames;
+};
+
+}