From 3fae41ef2291ffa6b71de2d5ce4503cf824a7c77 Mon Sep 17 00:00:00 2001
From: "Alexander A. Klimov" <alexander.klimov@icinga.com>
Date: Tue, 23 May 2023 14:41:35 +0200
Subject: [PATCH] Restart thread pool after freezing Configuration

The user (-D) or we could have changed Configuration.Concurrency,
so correct the thread pool's thread amount.
---
 icinga-app/icinga.cpp   |  2 ++
 lib/base/threadpool.cpp | 18 +++++++++++++++++-
 lib/base/threadpool.hpp |  3 +++
 3 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/icinga-app/icinga.cpp b/icinga-app/icinga.cpp
index f5b6809bc..5674a9ff2 100644
--- a/icinga-app/icinga.cpp
+++ b/icinga-app/icinga.cpp
@@ -451,6 +451,8 @@ static int Main()
 		Configuration::Concurrency = std::thread::hardware_concurrency();
 	}
 
+	Application::GetTP().Restart();
+
 	/* Ensure that all defined constants work in the way we expect them. */
 	HandleLegacyDefines();
 
diff --git a/lib/base/threadpool.cpp b/lib/base/threadpool.cpp
index 21f19fd42..dc76e7b15 100644
--- a/lib/base/threadpool.cpp
+++ b/lib/base/threadpool.cpp
@@ -20,10 +20,15 @@ void ThreadPool::Start()
 	boost::unique_lock<decltype(m_Mutex)> lock (m_Mutex);
 
 	if (!m_Pool) {
-		m_Pool = decltype(m_Pool)(new boost::asio::thread_pool(Configuration::Concurrency * 2u));
+		InitializePool();
 	}
 }
 
+void ThreadPool::InitializePool()
+{
+	m_Pool = decltype(m_Pool)(new boost::asio::thread_pool(Configuration::Concurrency * 2u));
+}
+
 void ThreadPool::Stop()
 {
 	boost::unique_lock<decltype(m_Mutex)> lock (m_Mutex);
@@ -33,3 +38,14 @@ void ThreadPool::Stop()
 		m_Pool = nullptr;
 	}
 }
+
+void ThreadPool::Restart()
+{
+	boost::unique_lock<decltype(m_Mutex)> lock (m_Mutex);
+
+	if (m_Pool) {
+		m_Pool->join();
+	}
+
+	InitializePool();
+}
diff --git a/lib/base/threadpool.hpp b/lib/base/threadpool.hpp
index f9760bc8b..d30fa694c 100644
--- a/lib/base/threadpool.hpp
+++ b/lib/base/threadpool.hpp
@@ -42,6 +42,7 @@ public:
 
 	void Start();
 	void Stop();
+	void Restart();
 
 	/**
 	 * Appends a work item to the work queue. Work items will be processed in FIFO order.
@@ -91,6 +92,8 @@ private:
 	boost::shared_mutex m_Mutex;
 	std::unique_ptr<boost::asio::thread_pool> m_Pool;
 	Atomic<uint_fast64_t> m_Pending;
+
+	void InitializePool();
 };
 
 }