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/* -*- C++ -*- */
// $Id$
#ifndef TAO_NOTIFY_ROUTING_SLIP_QUEUE_H
#define TAO_NOTIFY_ROUTING_SLIP_QUEUE_H
#include /**/ "ace/pre.h"
#include "Routing_Slip.h"
#if !defined (ACE_LACKS_PRAGMA_ONCE)
# pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */
namespace TAO_Notify
{
/**
* \brief A queue of Routing_Slips waiting to be persisted.
*
* The Routing_Slip_Queue keeps a queue of Routing_Slips waiting
* to be written to persistent storage. The "allowed" parameter
* determines how many Routing_Slips can be handled simultaneously
* by the persistent storage. Until this threshold is reached,
* Routing_Slips are not held in the queue, but pass straight through.
*
* Once the allowe number of Routing_Slips are being handled, any
* additional requests are held in the queue until persistence is
* complete for another Routing_Slips.
*
* Having Routing_Slips waiting in the queue is "a good thing" [TM]
* because it allows delivery completions to be applied to the
* routing slip before it is written -- thereby reducing or completely
* eliminating the number of actual writes to persistent storage.
*
* Experimentation indicates that a good value for "allowed" is 1.
*
* Allowed == 0 is treated as a special case meaning pass all Routing_Slips
* through the queue immediately. Setting it a good way to test how well
* your storage device withstands continuous beating.
*/
class TAO_Notify_Serv_Export Routing_Slip_Queue
{
typedef ACE_Unbounded_Queue <Routing_Slip_Ptr> Queue;
typedef ACE_Guard< TAO_SYNCH_MUTEX > Guard;
public:
/**
* \brief Construct setting "allowed".
* \param allowed the number of Routing_Slips that can be handled
* simultaneously by the persistent store.
*/
Routing_Slip_Queue (size_t allowed = 1);
/// Destructor.
~Routing_Slip_Queue ();
/**
* \brief Add a routing slip to the tail of the queue and dispatch if necessary.
*/
void add (const Routing_Slip_Ptr & routing_slip);
/**
* \brief A call back to indicate that processing is complete for a previously-queued
* Routing_Slip.
*/
void complete ();
/**
* /brief Adjust the "allowed" value on-the-fly (not recommended, but it works.)
*/
void set_allowed (size_t allowed);
private:
void dispatch (Guard & guard);
bool dispatch_one (Guard & guard);
private:
Routing_Slip_Queue (const Routing_Slip_Queue & rhs);
Routing_Slip_Queue & operator = (const Routing_Slip_Queue & rhs);
private:
// configuration setting
size_t allowed_;
/// Protection for internal information
TAO_SYNCH_MUTEX internals_;
size_t active_;
Queue queue_;
};
} // namespace
#if defined (__ACE_INLINE__)
#include "Routing_Slip_Queue.inl"
#endif /* __ACE_INLINE__ */
#include /**/ "ace/post.h"
#endif /* TAO_NOTIFY_ROUTING_SLIP_QUEUE_H */
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