ClickHouse/base/poco/Foundation/include/Poco/AsyncChannel.h

//
// AsyncChannel.h
//
// Library: Foundation
// Package: Logging
// Module:  AsyncChannel
//
// Definition of the AsyncChannel class.
//
// Copyright (c) 2004-2007, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier:	BSL-1.0
//


#ifndef Foundation_AsyncChannel_INCLUDED
#define Foundation_AsyncChannel_INCLUDED


#include "Poco/Channel.h"
#include "Poco/Foundation.h"
#include "Poco/Mutex.h"
#include "Poco/NotificationQueue.h"
#include "Poco/Runnable.h"
#include "Poco/Thread.h"


namespace Poco
{


class Foundation_API AsyncChannel : public Channel, public Runnable
/// A channel uses a separate thread for logging.
///
/// Using this channel can help to improve the performance of
/// applications that produce huge amounts of log messages or
/// that write log messages to multiple channels simultaneously.
///
/// All log messages are put into a queue and this queue is
/// then processed by a separate thread.
{
public:
    AsyncChannel(Channel * pChannel = 0, Thread::Priority prio = Thread::PRIO_NORMAL);
    /// Creates the AsyncChannel and connects it to
    /// the given channel.

    void setChannel(Channel * pChannel);
    /// Connects the AsyncChannel to the given target channel.
    /// All messages will be forwarded to this channel.

    Channel * getChannel() const;
    /// Returns the target channel.

    void open();
    /// Opens the channel and creates the
    /// background logging thread.

    void close();
    /// Closes the channel and stops the background
    /// logging thread.

    void log(const Message & msg);
    /// Queues the message for processing by the
    /// background thread.

    void setProperty(const std::string & name, const std::string & value);
    /// Sets or changes a configuration property.
    ///
    /// The "channel" property allows setting the target
    /// channel via the LoggingRegistry.
    /// The "channel" property is set-only.
    ///
    /// The "priority" property allows setting the thread
    /// priority. The following values are supported:
    ///    * lowest
    ///    * low
    ///    * normal (default)
    ///    * high
    ///    * highest
    ///
    /// The "priority" property is set-only.

protected:
    ~AsyncChannel();
    void run();
    void setPriority(const std::string & value);

private:
    Channel * _pChannel;
    Thread _thread;
    FastMutex _threadMutex;
    FastMutex _channelMutex;
    NotificationQueue _queue;
};


} // namespace Poco


#endif // Foundation_AsyncChannel_INCLUDED