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// -*- C++ -*-
//=============================================================================
/**
* @file CSD_TP_Task.h
*
* $Id$
*
* @author Tim Bradley <bradley_t@ociweb.com>
*/
//=============================================================================
#ifndef TAO_CSD_TP_TASK_H
#define TAO_CSD_TP_TASK_H
#include /**/ "ace/pre.h"
#include "tao/CSD_ThreadPool/CSD_TP_Export.h"
#include "tao/CSD_ThreadPool/CSD_TP_Queue.h"
#include "tao/PortableServer/PortableServer.h"
#include "tao/Condition.h"
#if !defined (ACE_LACKS_PRAGMA_ONCE)
# pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */
#include "ace/Task.h"
#include "ace/Synch.h"
#include "ace/Containers_T.h"
TAO_BEGIN_VERSIONED_NAMESPACE_DECL
namespace TAO
{
namespace CSD
{
/// Typedef for the number of threads.
typedef unsigned long Thread_Counter;
/**
* @class TP_Task
*
* @brief Active Object managing a queue of request objects.
*
* There are two types of "users" of a TP_Task object:
*
* 1) The TP_Strategy object that "owns" this task object.
* 2) The worker threads that "run" this task object as an
* "active object".
*
* The TP_Strategy object that "owns" this task object dictates
* when the worker threads are activated and when they are shutdown. It
* also injects requests into this task's queue via calls to the
* add_request() method. It is also the TP_Strategy object that
* dictates the number of worker threads to be activated via a call to
* the set_num_threads() method.
*
* The active object pattern is implemented via the use of the
* the ACE_Task_Base base class, and each worker thread will
* invoke this task's svc() method, and when the svc() returns, the
* worker thread will invoke this task's close() method (with the
* flag argument equal to 0).
*
* @note I just wanted to document an idea... When the pool consists
* of only one worker thread, we could care less about checking
* if target servant objects are busy or not. The simple fact
* that only one thread will be dispatching all requests means
* that servant objects will never be busy when the thread
* tests to see if a request is "ready_for_dispatch()". I'm
* just wondering if this knowledge can be applied to the
* implementation such that the "pool with one worker thread" case
* performs more efficiently. This is STP vs SSTP.
*
*/
class TAO_CSD_TP_Export TP_Task : public ACE_Task_Base
{
public:
/// Default Constructor.
TP_Task();
/// Virtual Destructor.
virtual ~TP_Task();
/// Put a request object on to the request queue.
/// Returns true if successful, false otherwise (it has been "rejected").
bool add_request(TP_Request* request);
/// Activate the worker threads
virtual int open(void* num_threads_ptr = 0);
/// The "mainline" executed by each worker thread.
virtual int svc();
/// Multi-purpose: argument value is used to differentiate purpose.
///
/// 0) Invoked by each worker thread after its invocation of the
/// svc() method has completed (ie, returned).
/// 1) Invoked by the strategy object to shutdown all worker threads.
virtual int close(u_long flag = 0);
/// Cancel all requests that are targeted for the provided servant.
void cancel_servant (PortableServer::Servant servant
ACE_ENV_ARG_DECL);
private:
typedef TAO_SYNCH_MUTEX LockType;
typedef ACE_Guard<LockType> GuardType;
typedef TAO_Condition<LockType> ConditionType;
/// Lock to protect the "state" (all of the data members) of this object.
LockType lock_;
/// Condition used to signal worker threads that they may be able to
/// find a request in the queue_ that needs to be dispatched to a
/// servant that is currently "not busy".
/// This condition will be signal()'ed each time a new request is
/// added to the queue_, and also when a servant has become "not busy".
ConditionType work_available_;
/// This condition will be signal()'ed each time the num_threads_
/// data member has its value changed. This is used to keep the
/// close(1) invocation (ie, a shutdown request) blocked until all
/// of the worker threads have stopped running.
ConditionType active_workers_;
/// Flag used to indicate when this task will (or will not) accept
/// requests via the the add_request() method.
bool accepting_requests_;
/// Flag used to initiate a shutdown request to all worker threads.
bool shutdown_initiated_;
/// Flag used to avoid multiple open() calls.
bool opened_;
/// The number of currently active worker threads.
Thread_Counter num_threads_;
/// The queue of pending servant requests (a.k.a. the "request queue").
TP_Queue queue_;
typedef ACE_Array <ACE_thread_t> Thread_Ids;
/// The list of ids for the threads launched by this task.
Thread_Ids activated_threads_;
};
}
}
TAO_END_VERSIONED_NAMESPACE_DECL
#if defined (__ACE_INLINE__)
# include "tao/CSD_ThreadPool/CSD_TP_Task.inl"
#endif /* __ACE_INLINE__ */
#include /**/ "ace/post.h"
#endif /* TAO_CSD_TP_TASK_H */
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