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//
// AsyncObserver.h
//
// Library: Foundation
// Package: Notifications
// Module: AsyncObserver
//
// Definition of the AsyncObserver class template.
//
// Copyright (c) 2006, Applied Informatics Software Engineering GmbH.
// Aleph ONE Software Engineering d.o.o.,
// and Contributors.
//
// SPDX-License-Identifier: BSL-1.0
//
#ifndef Foundation_AsyncObserver_INCLUDED
#define Foundation_AsyncObserver_INCLUDED
#include "Poco/Foundation.h"
#include "Poco/NObserver.h"
#include "Poco/Thread.h"
#include "Poco/Stopwatch.h"
#include "Poco/Debugger.h"
#include "Poco/ErrorHandler.h"
#include "Poco/Format.h"
#include "Poco/RunnableAdapter.h"
#include "Poco/NotificationQueue.h"
namespace Poco {
template <class C, class N>
class AsyncObserver: public NObserver<C, N>
/// AsyncObserver notifies subscribers in a dedicated thread (as opposed
/// to (N)Observer classes, which notify subscribers synchronously).
/// In order to become active and process notifications, the start()
/// method must be called.
///
/// This class is meant to be used with the NotificationCenter only.
/// Notification processing thread can be started only once, and copying
/// should be done before `start()` is called.
{
public:
using Type = AsyncObserver<C, N>;
using Matcher = typename NObserver<C, N>::Matcher;
using Handler = typename NObserver<C, N>::Handler;
using NotificationPtr = typename NObserver<C, N>::NotificationPtr;
AsyncObserver() = delete;
AsyncObserver(C& object, Handler handler, Matcher matcher = nullptr):
NObserver<C, N>(object, handler, matcher),
_ra(*this, &AsyncObserver::dequeue),
_started(false),
_done(false)
{
}
AsyncObserver(const AsyncObserver& observer):
NObserver<C, N>(observer),
_ra(*this, &AsyncObserver::dequeue),
_started(false),
_done(false)
{
poco_assert(observer._nq.size() == 0);
}
~AsyncObserver()
{
disable();
}
AsyncObserver& operator = (const AsyncObserver& observer)
{
if (&observer != this)
{
poco_assert(observer._nq.size() == 0);
setObject(observer._pObject);
setHandler(observer._handler);
setMatcher(observer._matcher);
_started = false;
_done =false;
}
return *this;
}
virtual void notify(Notification* pNf) const
{
_nq.enqueueNotification(NotificationPtr(static_cast<N*>(pNf), true));
}
virtual AbstractObserver* clone() const
{
return new AsyncObserver(*this);
}
virtual void start()
{
Poco::ScopedLock l(this->mutex());
if (_started)
{
throw Poco::InvalidAccessException(
Poco::format("thread already started %s", poco_src_loc));
}
_thread.start(_ra);
Poco::Stopwatch sw;
sw.start();
while (!_started)
{
if (sw.elapsedSeconds() > 5)
throw Poco::TimeoutException(poco_src_loc);
Thread::sleep(100);
}
}
virtual void disable()
{
if (!_started.exchange(false)) return;
_nq.wakeUpAll();
while (!_done) Thread::sleep(100);
_thread.join();
NObserver<C, N>::disable();
}
virtual int backlog() const
{
return _nq.size();
}
private:
void dequeue()
{
Notification::Ptr pNf;
_started = true;
_done = false;
while ((pNf = _nq.waitDequeueNotification()))
{
try
{
this->handle(pNf.unsafeCast<N>());
}
catch (Poco::Exception& ex)
{
Poco::ErrorHandler::handle(ex);
}
catch (std::exception& ex)
{
Poco::ErrorHandler::handle(ex);
}
catch (...)
{
Poco::ErrorHandler::handle();
}
}
_done = true;
_started = false;
}
using Adapter = RunnableAdapter<AsyncObserver<C, N>>;
Thread _thread;
mutable NotificationQueue _nq;
Adapter _ra;
std::atomic<bool> _started;
std::atomic<bool> _done;
};
} // namespace Poco
#endif // Foundation_AsyncObserver_INCLUDED
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