#2787: add queueSize property to the AsyncChannel

Foundation/include/Poco/AsyncChannel.h

@@ -50,14 +50,14 @@ public:
 	void setChannel(Channel::Ptr pChannel);
 		/// Connects the AsyncChannel to the given target channel.
 		/// All messages will be forwarded to this channel.
-		
+
 	Channel::Ptr getChannel() const;
 		/// Returns the target channel.
 
 	void open();
-		/// Opens the channel and creates the 
+		/// Opens the channel and creates the
 		/// background logging thread.
-		
+
 	void close();
 		/// Closes the channel and stops the background
 		/// logging thread.
@@ -69,7 +69,7 @@ public:
 	void setProperty(const std::string& name, const std::string& value);
 		/// Sets or changes a configuration property.
 		///
-		/// The "channel" property allows setting the target 
+		/// The "channel" property allows setting the target
 		/// channel via the LoggingRegistry.
 		/// The "channel" property is set-only.
 		///
@@ -82,18 +82,34 @@ public:
 		///    * highest
 		///
 		/// The "priority" property is set-only.
+		///
+		/// The "queueSize" property allows to limit the number
+		/// of messages in the queue. If the queue is full and
+		/// new messages are logged, these are dropped until the
+		/// queue has free capacity again. The number of dropped
+		/// messages is recorded, and a log message indicating the
+		/// number of dropped messages will be generated when the
+		/// queue has free capacity again.
+		/// In addition to an unsigned integer specifying the size,
+		/// this property can have the values "none" or "unlimited",
+		/// which disable the queue size limit. A size of 0 also
+		/// removes the limit.
+		///
+		/// The "queueSize" property is set-only.
 
 protected:
 	~AsyncChannel();
 	void run();
 	void setPriority(const std::string& value);
-		
+
 private:
-	Channel::Ptr      _pChannel;
+	Channel::Ptr _pChannel;
 	Thread    _thread;
 	FastMutex _threadMutex;
 	FastMutex _channelMutex;
 	NotificationQueue _queue;
+	std::size_t _queueSize = 0;
+	std::size_t _dropCount = 0;
 };
 
 

Foundation/src/AsyncChannel.cpp

@@ -18,7 +18,10 @@
 #include "Poco/Formatter.h"
 #include "Poco/AutoPtr.h"
 #include "Poco/LoggingRegistry.h"
+#include "Poco/NumberParser.h"
 #include "Poco/Exception.h"
+#include "Poco/String.h"
+#include "Poco/Format.h"
 
 
 namespace Poco {
@@ -31,23 +34,23 @@ public:
 		_msg(msg)
 	{
 	}
-	
+
 	~MessageNotification()
 	{
 	}
-	
+
 	const Message& message() const
 	{
 		return _msg;
 	}
-	
+
 private:
 	Message _msg;
 };
 
 
-AsyncChannel::AsyncChannel(Channel::Ptr pChannel, Thread::Priority prio): 
-	_pChannel(pChannel), 
+AsyncChannel::AsyncChannel(Channel::Ptr pChannel, Thread::Priority prio):
+	_pChannel(pChannel),
 	_thread("AsyncChannel")
 {
 	_thread.setPriority(prio);
@@ -70,7 +73,7 @@ AsyncChannel::~AsyncChannel()
 void AsyncChannel::setChannel(Channel::Ptr pChannel)
 {
 	FastMutex::ScopedLock lock(_channelMutex);
-	
+
 	_pChannel = pChannel;
 }
 
@@ -94,10 +97,10 @@ void AsyncChannel::close()
 	if (_thread.isRunning())
 	{
 		while (!_queue.empty()) Thread::sleep(100);
-		
-		do 
+
+		do
 		{
-			_queue.wakeUpAll(); 
+			_queue.wakeUpAll();
 		}
 		while (!_thread.tryJoin(100));
 	}
@@ -106,6 +109,18 @@ void AsyncChannel::close()
 
 void AsyncChannel::log(const Message& msg)
 {
+	if (_queueSize != 0 && _queue.size() >= _queueSize)
+	{
+		++_dropCount;
+		return;
+	}
+
+	if (_dropCount != 0)
+	{
+		_queue.enqueueNotification(new MessageNotification(Message(msg, Poco::format("Dropped %z messages.", _dropCount))));
+		_dropCount = 0;
+	}
+
 	open();
 
 	_queue.enqueueNotification(new MessageNotification(msg));
@@ -115,11 +130,24 @@ void AsyncChannel::log(const Message& msg)
 void AsyncChannel::setProperty(const std::string& name, const std::string& value)
 {
 	if (name == "channel")
+	{
 		setChannel(LoggingRegistry::defaultRegistry().channelForName(value));
+	}
 	else if (name == "priority")
+	{
 		setPriority(value);
+	}
+	else if (name == "queueSize")
+	{
+		if (Poco::icompare(value, "none") == 0 || Poco::icompare(value, "unlimited") == 0 || value.empty())
+			_queueSize = 0;
+		else
+			_queueSize = Poco::NumberParser::parseUnsigned(value);
+	}
 	else
+	{
 		Channel::setProperty(name, value);
+	}
 }
 
 
@@ -137,12 +165,12 @@ void AsyncChannel::run()
 		nf = _queue.waitDequeueNotification();
 	}
 }
-		
-		
+
+
 void AsyncChannel::setPriority(const std::string& value)
 {
 	Thread::Priority prio = Thread::PRIO_NORMAL;
-	
+
 	if (value == "lowest")
 		prio = Thread::PRIO_LOWEST;
 	else if (value == "low")
@@ -155,7 +183,7 @@ void AsyncChannel::setPriority(const std::string& value)
 		prio = Thread::PRIO_HIGHEST;
 	else
 		throw InvalidArgumentException("thread priority", value);
-		
+
 	_thread.setPriority(prio);
 }