Do not close connections before starting downloading

daemon/connect/Connection.cpp

@@ -3,7 +3,7 @@
  *
  *  Copyright (C) 2004 Sven Henkel <sidddy@users.sourceforge.net>
  *  Copyright (C) 2007-2019 Andrey Prygunkov <hugbug@users.sourceforge.net>
- *  Copyright (C) 2024-2025 Denis <denis@nzbget.com>
+ *  Copyright (C) 2024-2026 Denis <denis@nzbget.com>
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -172,27 +172,26 @@ bool Connection::Connect()
 	else
 	{
 		DoDisconnect();
+		m_status = csDisconnected;
 	}
 
 	return res;
 }
 
-bool Connection::Disconnect()
+void Connection::Disconnect()
 {
 	debug("Disconnecting");
 
 	if (m_status == csDisconnected)
 	{
-		return true;
+		return;
 	}
 
-	bool res = DoDisconnect();
+	DoDisconnect();
 
 	m_status = csDisconnected;
 	m_socket = INVALID_SOCKET;
 	m_bufAvail = 0;
-
-	return res;
 }
 
 bool Connection::Bind()
@@ -853,7 +852,7 @@ bool Connection::ConnectWithTimeout(void* address, int address_len)
 	return true;
 }
 
-bool Connection::DoDisconnect()
+void Connection::DoDisconnect()
 {
 	debug("Do disconnecting");
 
@@ -883,7 +882,6 @@ bool Connection::DoDisconnect()
 	}
 
 	m_status = csDisconnected;
-	return true;
 }
 
 void Connection::ReadBuffer(char** buffer, int *bufLen)

daemon/connect/Connection.h

@@ -3,7 +3,7 @@
  *
  *  Copyright (C) 2004 Sven Henkel <sidddy@users.sourceforge.net>
  *  Copyright (C) 2007-2017 Andrey Prygunkov <hugbug@users.sourceforge.net>
- *  Copyright (C) 2024-2025 Denis <denis@nzbget.com>
+ *  Copyright (C) 2024-2026 Denis <denis@nzbget.com>
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -55,7 +55,7 @@ class Connection
 	static void Init();
 	static void Final();
 	virtual bool Connect();
-	virtual bool Disconnect();
+	virtual void Disconnect();
 	bool Bind();
 	bool Send(const char* buffer, int size);
 	bool Recv(char* buffer, int size);
@@ -130,7 +130,7 @@ class Connection
 	virtual void PrintError(const char* errMsg);
 	int GetLastNetworkError();
 	bool DoConnect();
-	bool DoDisconnect();
+	void DoDisconnect();
 	bool InitSocketOpts(SOCKET socket);
 	bool ConnectWithTimeout(void* address, int address_len);
 #ifndef HAVE_GETADDRINFO

daemon/nntp/ArticleDownloader.cpp

@@ -283,7 +283,7 @@ void ArticleDownloader::Run()
 		}
 	}
 
-	FreeConnection(status == adFinished);
+	FreeConnection(status == adFinished || (status == adRetry && m_connection && m_connection->GetStatus() == Connection::csConnected));
 
 	if (m_articleWriter.GetDuplicate())
 	{

daemon/nntp/NewsServer.cpp

@@ -3,6 +3,7 @@
  *
  *  Copyright (C) 2004 Sven Henkel <sidddy@users.sourceforge.net>
  *  Copyright (C) 2007-2016 Andrey Prygunkov <hugbug@users.sourceforge.net>
+ *  Copyright (C) 2026 Denis <denis@nzbget.com>
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -35,3 +36,36 @@ NewsServer::NewsServer(int id, bool active, const char* name, const char* host,
 		m_name.Format("server%i", id);
 	}
 }
+
+void NewsServer::DelayConnect()
+{
+	constexpr std::chrono::milliseconds CONNECTION_DELAY{15};
+	using Clock = std::chrono::steady_clock;
+
+	Clock::time_point deadline{Clock::time_point::max()};
+
+	{
+		std::lock_guard<std::mutex> lock(m_connectMutex);
+
+		auto now = Clock::now();
+		if (m_lastConnectTime == Clock::time_point::min())
+		{
+			m_lastConnectTime = now;
+			return;
+		}
+
+		if (now >= m_lastConnectTime + CONNECTION_DELAY)
+		{
+			m_lastConnectTime = now;
+			return;
+		}
+
+		m_lastConnectTime += CONNECTION_DELAY;
+		deadline = m_lastConnectTime;
+	}
+
+	if (deadline != Clock::time_point::max())
+	{
+		std::this_thread::sleep_until(deadline);
+	}
+}

daemon/nntp/NewsServer.h

@@ -3,7 +3,7 @@
  *
  *  Copyright (C) 2004 Sven Henkel <sidddy@users.sourceforge.net>
  *  Copyright (C) 2007-2015 Andrey Prygunkov <hugbug@users.sourceforge.net>
- *  Copyright (C) 2025 Denis <denis@nzbget.com>
+ *  Copyright (C) 2025-2026 Denis <denis@nzbget.com>
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -28,6 +28,8 @@
 #ifndef NEWSSERVER_H
 #define NEWSSERVER_H
 
+#include <chrono>
+#include <mutex>
 #include "NString.h"
 
 class NewsServer
@@ -62,6 +64,14 @@ class NewsServer
 	void SetBlockTime(time_t blockTime) { m_blockTime = blockTime; }
 	unsigned int GetCertVerificationLevel() const { return m_certVerificationfLevel; }
 
+	/**
+	 * @brief Delays the connection attempt to enforce a minimum interval of 15ms between connections.
+	 * 
+	 * This rate limiter prevents "502 Too Many Connections" and "481 Exceeded Maximum Connections"
+	 * errors on Usenet servers by spacing out rapid connection attempts.
+	 */
+	void DelayConnect();
+
 private:
 	int m_id;
 	int m_stateId = 0;
@@ -83,6 +93,8 @@ class NewsServer
 	bool m_optional = false;
 	time_t m_blockTime = 0;
 	unsigned int m_certVerificationfLevel;
+	std::chrono::steady_clock::time_point m_lastConnectTime{std::chrono::steady_clock::time_point::min()};
+	std::mutex m_connectMutex;
 };
 
 typedef std::vector<std::unique_ptr<NewsServer>> Servers;

daemon/nntp/NntpConnection.cpp

@@ -3,6 +3,7 @@
  *
  *  Copyright (C) 2004 Sven Henkel <sidddy@users.sourceforge.net>
  *  Copyright (C) 2007-2016 Andrey Prygunkov <hugbug@users.sourceforge.net>
+ *  Copyright (C) 2024-2026 Denis <denis@nzbget.com>
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -195,6 +196,11 @@ bool NntpConnection::Connect()
 		return true;
 	}
 
+	if (m_newsServer)
+	{
+		m_newsServer->DelayConnect();
+	}
+
 	if (!Connection::Connect())
 	{
 		return false;
@@ -227,14 +233,14 @@ bool NntpConnection::Connect()
 	return true;
 }
 
-bool NntpConnection::Disconnect()
+void NntpConnection::Disconnect()
 {
 	if (m_status == csConnected)
 	{
 		Request("quit\r\n");
 		m_activeGroup = nullptr;
 	}
-	return Connection::Disconnect();
+	Connection::Disconnect();
 }
 
 void NntpConnection::ReportErrorAnswer(const char* msgPrefix, const char* answer)

daemon/nntp/NntpConnection.h

@@ -3,6 +3,7 @@
  *
  *  Copyright (C) 2004 Sven Henkel <sidddy@users.sourceforge.net>
  *  Copyright (C) 2007-2016 Andrey Prygunkov <hugbug@users.sourceforge.net>
+ *  Copyright (C) 2026 Denis <denis@nzbget.com>
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -30,8 +31,8 @@ class NntpConnection : public Connection
 {
 public:
 	NntpConnection(NewsServer* newsServer);
-	virtual bool Connect();
-	virtual bool Disconnect();
+	bool Connect() override;
+	void Disconnect() override;
 	NewsServer* GetNewsServer() { return m_newsServer; }
 	const char* Request(const char* req);
 	const char* JoinGroup(const char* grp);

daemon/nntp/ServerPool.cpp

@@ -3,7 +3,7 @@
  *
  *  Copyright (C) 2004 Sven Henkel <sidddy@users.sourceforge.net>
  *  Copyright (C) 2007-2016 Andrey Prygunkov <hugbug@users.sourceforge.net>
- *  Copyright (C) 2024 Denis <denis@nzbget.com>
+ *  Copyright (C) 2024-2026 Denis <denis@nzbget.com>
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -23,8 +23,9 @@
 #include "nzbget.h"
 #include "ServerPool.h"
 #include "Util.h"
+#include "QueueCoordinator.h"
 
-static const int CONNECTION_HOLD_SECODNS = 5;
+static constexpr int CONNECTION_HOLD_SECONDS = 30;
 
 void ServerPool::PooledConnection::SetFreeTimeNow()
 {
@@ -113,7 +114,7 @@ void ServerPool::InitConnections()
 {
 	debug("Initializing connections in ServerPool");
 
-	Guard guard(m_connectionsMutex);
+	std::lock_guard<std::mutex> guard(m_connectionsMutex);
 
 	NormalizeLevels();
 	m_levels.clear();
@@ -162,7 +163,7 @@ void ServerPool::InitConnections()
  */
 NntpConnection* ServerPool::GetConnection(int level, NewsServer* wantServer, RawServerList* ignoreServers)
 {
-	Guard guard(m_connectionsMutex);
+	std::lock_guard<std::mutex> guard(m_connectionsMutex);
 
 	for (; level < (int)m_levels.size() && m_levels[level] > 0; level++)
 	{
@@ -256,7 +257,7 @@ void ServerPool::FreeConnection(NntpConnection* connection, bool used)
 		debug("Freeing used connection");
 	}
 
-	Guard guard(m_connectionsMutex);
+	std::lock_guard<std::mutex> guard(m_connectionsMutex);
 
 	((PooledConnection*)connection)->SetInUse(false);
 	if (used)
@@ -274,7 +275,7 @@ void ServerPool::BlockServer(NewsServer* newsServer)
 {
 	bool newBlock = false;
 	{
-		Guard guard(m_connectionsMutex);
+		std::lock_guard<std::mutex> guard(m_connectionsMutex);
 		time_t curTime = Util::CurrentTime();
 		newBlock = newsServer->GetBlockTime() != curTime;
 		newsServer->SetBlockTime(curTime);
@@ -301,7 +302,7 @@ bool ServerPool::IsServerBlocked(NewsServer* newsServer)
 
 void ServerPool::CloseUnusedConnections()
 {
-	Guard guard(m_connectionsMutex);
+	std::lock_guard<std::mutex> guard(m_connectionsMutex);
 
 	time_t curtime = Util::CurrentTime();
 
@@ -350,9 +351,11 @@ void ServerPool::CloseUnusedConnections()
 			}
 		}
 
-		// if there are no in-use connections on the level and the hold time out has
-		// expired - close all connections of the level.
-		if (!hasInUseConnections && inactiveTime > CONNECTION_HOLD_SECODNS)
+		// If there are no in-use connections on the level and the hold timeout has expired,
+		// close all connections of that level. For the primary level (level 0), we keep
+		// connections alive as long as the queue has more jobs
+		if (!hasInUseConnections && inactiveTime > CONNECTION_HOLD_SECONDS &&
+			(level > 0 || !g_QueueCoordinator || !g_QueueCoordinator->HasMoreJobs()))
 		{
 			for (PooledConnection* connection : &m_connections)
 			{
@@ -381,7 +384,7 @@ void ServerPool::LogDebugInfo()
 
 	info("    Max-Level: %i", m_maxNormLevel);
 
-	Guard guard(m_connectionsMutex);
+	std::lock_guard<std::mutex> guard(m_connectionsMutex);
 
 	time_t curTime = Util::CurrentTime();
 

daemon/nntp/ServerPool.h

@@ -3,7 +3,7 @@
  *
  *  Copyright (C) 2004 Sven Henkel <sidddy@users.sourceforge.net>
  *  Copyright (C) 2007-2016 Andrey Prygunkov <hugbug@users.sourceforge.net>
- *  Copyright (C) 2024 Denis <denis@nzbget.com>
+ *  Copyright (C) 2024-2026 Denis <denis@nzbget.com>
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -24,12 +24,10 @@
 #define SERVERPOOL_H
 
 #include "Log.h"
-#include "Container.h"
-#include "Thread.h"
 #include "NewsServer.h"
 #include "NntpConnection.h"
 
-class ServerPool : public Debuggable
+class ServerPool final : public Debuggable
 {
 public:
 	typedef std::vector<NewsServer*> RawServerList;
@@ -50,10 +48,10 @@ class ServerPool : public Debuggable
 	bool IsServerBlocked(NewsServer* newsServer);
 
 protected:
-	virtual void LogDebugInfo();
+	void LogDebugInfo() override;
 
 private:
-	class PooledConnection : public NntpConnection
+	class PooledConnection final : public NntpConnection
 	{
 	public:
 		using NntpConnection::NntpConnection;
@@ -62,8 +60,8 @@ class ServerPool : public Debuggable
 		time_t GetFreeTime() { return m_freeTime; }
 		void SetFreeTimeNow();
 	private:
-		bool m_inUse = false;
 		time_t m_freeTime = 0;
+		bool m_inUse = false;
 	};
 
 	typedef std::vector<int> Levels;
@@ -73,8 +71,8 @@ class ServerPool : public Debuggable
 	RawServerList m_sortedServers;
 	Connections m_connections;
 	Levels m_levels;
+	std::mutex m_connectionsMutex;
 	int m_maxNormLevel = 0;
-	Mutex m_connectionsMutex;
 	int m_timeout = 60;
 	int m_retryInterval = 0;
 	int m_generation = 0;