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// -*- C++ -*-
//=============================================================================
/**
* @file LB_LeastLoaded.h
*
* $Id$
*
* @author Ossama Othman <ossama@uci.edu>
*/
//=============================================================================
#ifndef LB_LEAST_LOADED_H
#define LB_LEAST_LOADED_H
#include /**/ "ace/pre.h"
#include "LB_LoadMap.h"
# if !defined (ACE_LACKS_PRAGMA_ONCE)
# pragma once
# endif /* ACE_LACKS_PRAGMA_ONCE */
#include "orbsvcs/CosLoadBalancingS.h"
#include "ace/Synch_Traits.h"
#include "ace/Thread_Mutex.h"
namespace TAO_LB
{
/**
* @name Default LeastLoaded strategy parameters.
*
* Defaults defined by the Load Balancing specification.
*/
//@{
const CORBA::Float LL_DEFAULT_CRITICAL_THRESHOLD = 0;
const CORBA::Float LL_DEFAULT_REJECT_THRESHOLD = 0;
const CORBA::Float LL_DEFAULT_TOLERANCE = 1;
const CORBA::Float LL_DEFAULT_DAMPENING = 0;
const CORBA::Float LL_DEFAULT_PER_BALANCE_LOAD = 0;
//@}
/**
* @name TAO-specific LeastLoaded strategy parameters.
*
* Parameters internal to TAO's LeastLoaded strategy
* implementation.
*/
//@{
/// Percentage difference between two load values that determines
/// whether the loads are considered equivalent.
/**
* If the percent difference between two loads, i.e.:
* (Old Load - New Load) / New Load
* is less than or equal to this value, the two loads will be
* considered equivalent. In such a case, an object group member
* residing at the location corresponding to one of the two loads
* will be selected at random.
*/
const CORBA::Float LL_DEFAULT_LOAD_PERCENT_DIFF_CUTOFF = 0.01f; // 1%
//@}
}
/**
* @class TAO_LB_LeastLoaded
*
* @brief "Least loaded" load balancing strategy
*
* This load balancing strategy is designed to select an object group
* member residing at a location with the smallest load.
*/
class TAO_LB_LeastLoaded
: public virtual POA_CosLoadBalancing::Strategy,
public virtual PortableServer::RefCountServantBase
{
public:
/// Constructor.
TAO_LB_LeastLoaded (PortableServer::POA_ptr poa);
/**
* @name CosLoadBalancing::Strategy methods
*
* Methods required by the CosLoadBalancing::Strategy interface.
*/
//@{
virtual char * name (ACE_ENV_SINGLE_ARG_DECL_WITH_DEFAULTS)
ACE_THROW_SPEC ((CORBA::SystemException));
virtual CosLoadBalancing::Properties * get_properties (
ACE_ENV_SINGLE_ARG_DECL_WITH_DEFAULTS)
ACE_THROW_SPEC ((CORBA::SystemException));
virtual void push_loads (
const PortableGroup::Location & the_location,
const CosLoadBalancing::LoadList & loads
ACE_ENV_ARG_DECL_WITH_DEFAULTS)
ACE_THROW_SPEC ((CORBA::SystemException));
virtual CosLoadBalancing::LoadList * get_loads (
CosLoadBalancing::LoadManager_ptr load_manager,
const PortableGroup::Location & the_location
ACE_ENV_ARG_DECL_WITH_DEFAULTS)
ACE_THROW_SPEC ((CORBA::SystemException,
CosLoadBalancing::LocationNotFound));
virtual CORBA::Object_ptr next_member (
PortableGroup::ObjectGroup_ptr object_group,
CosLoadBalancing::LoadManager_ptr load_manager
ACE_ENV_ARG_DECL_WITH_DEFAULTS)
ACE_THROW_SPEC ((CORBA::SystemException,
PortableGroup::ObjectGroupNotFound,
PortableGroup::MemberNotFound));
virtual void analyze_loads (
PortableGroup::ObjectGroup_ptr object_group,
CosLoadBalancing::LoadManager_ptr load_manager
ACE_ENV_ARG_DECL_WITH_DEFAULTS)
ACE_THROW_SPEC ((CORBA::SystemException));
//@}
/// Returns the default POA for this servant.
virtual PortableServer::POA_ptr _default_POA (
ACE_ENV_SINGLE_ARG_DECL_WITH_DEFAULTS
);
/// Initialize the LeastLoaded instance with the given properties.
void init (const PortableGroup::Properties & props
ACE_ENV_ARG_DECL);
protected:
/// Destructor.
~TAO_LB_LeastLoaded (void);
/// Retrieve the least loaded location from the given list of
/// locations.
CORBA::Boolean get_location (CosLoadBalancing::LoadManager_ptr load_manager,
const PortableGroup::Locations & locations,
PortableGroup::Location & location
ACE_ENV_ARG_DECL);
/// Return the effective load.
CORBA::Float effective_load (CORBA::Float previous_load,
CORBA::Float new_load);
/// Push the new load into this Strategy's load processor, and
/// return the corresponding effective load.
void push_loads (
const PortableGroup::Location & the_location,
const CosLoadBalancing::LoadList & loads,
CosLoadBalancing::Load & effective_load
ACE_ENV_ARG_DECL);
/// Utility method to extract a CORBA::Float value from the given
/// property.
void extract_float_property (const PortableGroup::Property & property,
CORBA::Float & value
ACE_ENV_ARG_DECL);
private:
/// This servant's default POA.
PortableServer::POA_var poa_;
/// Table that maps location to load list.
TAO_LB_LoadMap * load_map_;
/// Lock used to ensure atomic access to state retained by this
/// class.
TAO_SYNCH_MUTEX * lock_;
/// Cached set of properties used when initializing this strategy.
CosLoadBalancing::Properties properties_;
/**
* @name LeastLoaded Property Values
*
* Cached LeastLoaded load balancing strategy property values.
*/
//@{
/// The critical load threshold.
/**
* Load rebalancing/shedding will occur if loads at a given location
* are greater than this value. The default value is zero, which
* indicates that no load rebalancing/shedding will occur.
*/
CORBA::Float critical_threshold_;
/// The request rejection threshold.
/**
* If the load at a given location is greater than this value, the
* member at that location will not be considered when choosing a
* member to the request will be forwarded. If all locations have
* loads greater than this value, a @c CORBA::TRANSIENT exception
* will be thrown unless the reject threshold is zero, which is the
* default. If the request rejection threshold is zero, a @c
* CORBA::TRANSIENT will not be thrown by this load balancing
* strategy, unless no object group members have been added yet.
*/
CORBA::Float reject_threshold_;
///
CORBA::Float tolerance_;
///
CORBA::Float dampening_;
///
CORBA::Float per_balance_load_;
//@}
};
#if defined (__ACE_INLINE__)
#include "LB_LeastLoaded.inl"
#endif /* defined INLINE */
#include /**/ "ace/post.h"
#endif /* LB_LEAST_LOADED_H */
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