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/* -*- C++ -*- */
// $Id$
// ============================================================================
//
// = LIBRARY
// ace
//
// = FILENAME
// TP_Reactor.h
//
// = DESCRIPTION
// TP_Reactor (ala, Thread Pool Reactor) uses the leader-follower
// model to demultiplex requests among a bunch of threads.
// Basically, when using thread pool reactor, one will pre-spawn a
// _fixed_ number of threads. When you issue the run_event_loop ()
// method, one of the thread will become the leader thread and wait
// for an event. The other threads (followers) will be lined up
// and waiting for their turns to become the leader. When an event
// occurs, the leader will pick a follower to become the leader and
// go on to handle the event. The consequence of using TP_Reactor
// is the amortization of the costs used to creating threads. The
// context switching cost will also reduce. More over, the total
// resources used by threads are bounded (because there are only so
// many threads.)
//
// = AUTHOR
// Irfan Pyarali
// Nanbor Wang
//
// ============================================================================
#ifndef ACE_TP_REACTOR_H
#define ACE_TP_REACTOR_H
#include "ace/Select_Reactor.h"
#if !defined (ACE_LACKS_PRAGMA_ONCE)
# pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */
class ACE_Export ACE_EH_Dispatch_Info
{
// = TITLE
//
// This structure contains information of the activated event
// handler.
public:
ACE_EH_Dispatch_Info (void);
void set (ACE_HANDLE handle,
ACE_Event_Handler *event_handler,
ACE_Reactor_Mask mask,
ACE_EH_PTMF callback);
void reset (void);
int dispatch (void) const;
ACE_HANDLE handle_;
ACE_Event_Handler *event_handler_;
ACE_Reactor_Mask mask_;
ACE_EH_PTMF callback_;
int dispatch_;
};
class ACE_Export ACE_TP_Reactor : public ACE_Select_Reactor
{
// = TITLE
//
// Specialization of Select Reactor to support thread-pool based
// event dispatching.
//
// = DESCRIPTION
//
// One of the short comings of the Select_Reactor in ACE is that
// it did not support a thread pool based event dispatching
// model, similar to the one in WFMO_Reactor. In
// Select_Reactor, only thread can be blocked in handle_events()
// at any given time.
//
// A new Reactor has been added to ACE that removes this
// short-coming. TP_Reactor is a specialization of Select
// Reactor to support thread-pool based event dispatching. This
// Reactor takes advantage of the fact that events reported by
// select() are persistent if not acted upon immediately. It
// works by remembering the event handler that just got
// activated, releasing the internal lock (so that some other
// thread can start waiting in the event loop) and then
// dispatching the event handler outside the context of the
// Reactor lock.
//
// This Reactor is best suited for situations when the callbacks
// to event handlers can take arbitrarily long and/or a number
// of threads are available to run the event loops.
//
// Note that callback code in Event Handlers
// (e.g. Event_Handler::handle_input) does not have to be
// modified or made thread-safe for this Reactor. This is
// because an activated Event Handler is suspended in the
// Reactor before the upcall is made and resumed after the
// upcall completes. Therefore, one Event Handler cannot be
// called by multiple threads simultaneously.
public:
// = Initialization and termination methods.
ACE_TP_Reactor (ACE_Sig_Handler * = 0,
ACE_Timer_Queue * = 0);
// Initialize <ACE_TP_Reactor> with the default size.
ACE_TP_Reactor (size_t size,
int restart = 0,
ACE_Sig_Handler * = 0,
ACE_Timer_Queue * = 0);
// Initialize <ACE_TP_Reactor> with size <size>.
// = Event loop drivers.
virtual int handle_events (ACE_Time_Value *max_wait_time = 0);
// This event loop driver that blocks for <max_wait_time> before
// returning. It will return earlier if timer events, I/O events,
// or signal events occur. Note that <max_wait_time> can be 0, in
// which case this method blocks indefinitely until events occur.
//
// <max_wait_time> is decremented to reflect how much time this call
// took. For instance, if a time value of 3 seconds is passed to
// handle_events and an event occurs after 2 seconds,
// <max_wait_time> will equal 1 second. This can be used if an
// application wishes to handle events for some fixed amount of
// time.
//
// Returns the total number of <ACE_Event_Handler>s that were
// dispatched, 0 if the <max_wait_time> elapsed without dispatching
// any handlers, or -1 if something goes wrong.
virtual int handle_events (ACE_Time_Value &max_wait_time);
static void no_op_sleep_hook (void *);
// Called from handle events
virtual void wakeup_all_threads (void);
// Wake up all threads in waiting in the event loop
ACE_ALLOC_HOOK_DECLARE;
// Declare the dynamic allocation hooks.
protected:
// = Internal methods that do the actual work.
virtual int dispatch_io_set (int number_of_active_handles,
int& number_dispatched,
int mask,
ACE_Handle_Set& dispatch_mask,
ACE_Handle_Set& ready_mask,
ACE_EH_PTMF callback);
// Overwrites ACE_Select_Reactor::dispatch_io_set() to *not*
// dispatch any event handlers. The information of one activated
// event handler is stored away, so that the event handler can be
// dispatch later.
virtual void notify_handle (ACE_HANDLE handle,
ACE_Reactor_Mask mask,
ACE_Handle_Set &,
ACE_Event_Handler *eh,
ACE_EH_PTMF callback);
// This method shouldn't get called.
virtual int notify_handle (ACE_EH_Dispatch_Info &dispatch_info);
// Notify the appropriate <callback> in the context of the <eh>
// associated with <handle> that a particular event has occurred.
ACE_EH_Dispatch_Info dispatch_info_;
// Dispatch information of the activated event handler
private:
ACE_TP_Reactor (const ACE_TP_Reactor &);
ACE_TP_Reactor &operator = (const ACE_TP_Reactor &);
// Deny access since member-wise won't work...
};
#if defined (__ACE_INLINE__)
#include "ace/TP_Reactor.i"
#endif /* __ACE_INLINE__ */
#endif /* ACE_TP_REACTOR_H */
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