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// $Id$
// ============================================================================
//
// = LIBRARY
// TAO
//
// = FILENAME
// Leader_Follower.h
//
// = AUTHOR
// Carlos O'Ryan (coryan@cs.wustl.edu)
//
// ============================================================================
#ifndef TAO_LEADER_FOLLOWER_H
#define TAO_LEADER_FOLLOWER_H
#include "tao/ORB_Core.h"
#if !defined (ACE_LACKS_PRAGMA_ONCE)
# pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */
#include "ace/Containers_T.h"
class TAO_Export TAO_Leader_Follower
{
public:
TAO_Leader_Follower (TAO_ORB_Core *orb_core);
// Constructor
~TAO_Leader_Follower (void);
// Destructor
int set_event_loop_thread (ACE_Time_Value *max_wait_time);
// The current thread has become a server thread (i.e. called
// ORB::run), update any flags and counters.
void reset_event_loop_thread (void);
// The current thread is not a server thread anymore, reset any
// flags and counters.
int leader_available (void) const;
// Is there any thread running as a leader?
void set_client_thread (void);
// A server thread is making a request.
void reset_client_thread (void);
// A server thread has finished is making a request.
void set_client_leader_thread (void) ;
// The current thread has become the leader thread in the
// client side leader-follower set.
void reset_client_leader_thread (void) ;
// The current thread is no longer the leader thread in the client
// side leader-follower set.
void set_client_leader_thread (ACE_thread_t thread_ID);
// sets the thread ID of the leader thread in the leader-follower
// model
int is_client_leader_thread (void) const;
// checks if we are a leader thread
int elect_new_leader (void);
// A leader thread is relinquishing its role, unless there are more
// leader threads running pick up a follower (if there is any) to
// play the leader role.
int add_follower (ACE_SYNCH_CONDITION *follower_ptr);
// adds the a follower to the set of followers in the leader-
// follower model
// returns 0 on success, -1 on failure and 1 if the element is
// already there.
int follower_available (void) const;
// checks for the availablity of a follower
// returns 1 on available, 0 else
int remove_follower (ACE_SYNCH_CONDITION *follower_ptr);
// removes a follower from the leader-follower set
// returns 0 on success, -1 on failure
ACE_SYNCH_CONDITION *get_next_follower (void);
// returns randomly a follower from the leader-follower set
// returns follower on success, else 0
ACE_SYNCH_MUTEX &lock (void);
ACE_Reverse_Lock<ACE_SYNCH_MUTEX> &reverse_lock (void);
// Accessors
int has_clients (void) const;
// Check if there are any client threads running
ACE_Reactor *reactor (void);
// Accesor to the reactor
private:
TAO_ORB_Core_TSS_Resources *get_tss_resources (void) const;
// Shortcut to obtain the TSS resources of the orb core.
int wait_for_client_leader_to_complete (ACE_Time_Value *max_wait_time);
// Wait for the client leader to complete.
private:
TAO_ORB_Core *orb_core_;
// The orb core
ACE_SYNCH_MUTEX lock_;
// To synchronize access to the members.
ACE_Reverse_Lock<ACE_SYNCH_MUTEX> reverse_lock_;
// do protect the access to the following three members
ACE_Unbounded_Set<ACE_SYNCH_CONDITION *> follower_set_;
// keep a set of followers around (protected)
int leaders_;
// Count the number of active leaders.
// There could be many leaders in the thread pool (i.e. calling
// ORB::run), and the same leader could show up multiple times as it
// receives nested upcalls and sends more requests.
int clients_;
// Count the number of active clients, this is useful to know when
// to deactivate the reactor
ACE_Reactor *reactor_;
// The reactor
int client_thread_is_leader_;
// Is a client thread the current leader?
int event_loop_threads_waiting_;
// Are server threads waiting for the client leader to complete?
ACE_SYNCH_CONDITION event_loop_threads_condition_;
// Condition variable for server threads waiting for the client
// leader to complete.
};
class TAO_Export TAO_LF_Client_Thread_Helper
{
public:
TAO_LF_Client_Thread_Helper (TAO_Leader_Follower &leader_follower);
// Constructor
~TAO_LF_Client_Thread_Helper (void);
// Destructor
private:
TAO_Leader_Follower &leader_follower_;
// Reference to leader/followers object.
};
class TAO_Export TAO_LF_Client_Leader_Thread_Helper
{
public:
TAO_LF_Client_Leader_Thread_Helper (TAO_Leader_Follower &leader_follower);
// Constructor
~TAO_LF_Client_Leader_Thread_Helper (void);
// Destructor
private:
TAO_Leader_Follower &leader_follower_;
// Reference to leader/followers object.
};
class TAO_Export TAO_LF_Event_Loop_Thread_Helper
{
public:
TAO_LF_Event_Loop_Thread_Helper (TAO_Leader_Follower &leader_follower);
// Constructor
~TAO_LF_Event_Loop_Thread_Helper (void);
// Destructor
int set_event_loop_thread (ACE_Time_Value *max_wait_time);
// Calls <set_event_loop_thread> on the leader/followers object.
private:
TAO_Leader_Follower &leader_follower_;
// Reference to leader/followers object.
int call_reset_;
// Remembers whether we have to call the reset method in the
// destructor.
};
#if defined (__ACE_INLINE__)
# include "tao/Leader_Follower.i"
#endif /* __ACE_INLINE__ */
#endif /* TAO_LEADER_FOLLOWER_H */
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