From 087c8b535434a5a40034104a74c547433f011aad Mon Sep 17 00:00:00 2001
From: Yonas Habteab <yonas.habteab@icinga.com>
Date: Tue, 13 Feb 2024 14:52:20 +0100
Subject: [PATCH] ApiListener: Process cluster config updates sequentially

---
 lib/remote/apilistener-configsync.cpp | 15 +++++++++++++++
 lib/remote/apilistener.hpp            |  3 +++
 2 files changed, 18 insertions(+)

diff --git a/lib/remote/apilistener-configsync.cpp b/lib/remote/apilistener-configsync.cpp
index f19092ffc73..b0384adba17 100644
--- a/lib/remote/apilistener-configsync.cpp
+++ b/lib/remote/apilistener-configsync.cpp
@@ -7,6 +7,7 @@
 #include "base/configtype.hpp"
 #include "base/json.hpp"
 #include "base/convert.hpp"
+#include "base/defer.hpp"
 #include "config/vmops.hpp"
 #include <fstream>
 
@@ -104,6 +105,13 @@ Value ApiListener::ConfigUpdateObjectAPIHandler(const MessageOrigin::Ptr& origin
 		return Empty;
 	}
 
+	// Wait for the object name to become available for processing and block it immediately.
+	listener->m_ObjectConfigChangeLock.WaitForObject(ptype, objName);
+
+	Defer unlockAndNotifyOne([&listener, &ptype, &objName]{
+		listener->m_ObjectConfigChangeLock.UnBlockNotify(ptype, objName);
+	});
+
 	ConfigObject::Ptr object = ctype->GetObject(objName);
 
 	String config = params->Get("config");
@@ -258,6 +266,13 @@ Value ApiListener::ConfigDeleteObjectAPIHandler(const MessageOrigin::Ptr& origin
 		return Empty;
 	}
 
+	// Wait for the object name to become available for processing and block it immediately.
+	listener->m_ObjectConfigChangeLock.WaitForObject(ptype, objName);
+
+	Defer unblockAndNotifyOne([&listener, &ptype, &objName]{
+		listener->m_ObjectConfigChangeLock.UnBlockNotify(ptype, objName);
+	});
+
 	ConfigObject::Ptr object = ctype->GetObject(objName);
 
 	if (!object) {
diff --git a/lib/remote/apilistener.hpp b/lib/remote/apilistener.hpp
index 2f653d8f0ac..ae5fadeb507 100644
--- a/lib/remote/apilistener.hpp
+++ b/lib/remote/apilistener.hpp
@@ -271,6 +271,9 @@ class ApiListener final : public ObjectImpl<ApiListener>
 	mutable std::mutex m_ActivePackageStagesLock;
 	std::map<String, String> m_ActivePackageStages;
 
+	/* ensures that at most one create/update/delete is being processed per object at each time */
+	mutable ObjectNameMutex m_ObjectConfigChangeLock;
+
 	void UpdateActivePackageStagesCache();
 };