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// -*- C++ -*-
// $Id$
#include "Minimum_Dispersion.h"
#include "ReplicaProxy.h"
ACE_RCSID(orbsvcs, Minimum_Dispersion, "$Id$")
TAO_LB_Minimum_Dispersion_Strategy::TAO_LB_Minimum_Dispersion_Strategy (void)
: proxies_ (),
lock_ ()
{
}
TAO_LB_Minimum_Dispersion_Strategy::~TAO_LB_Minimum_Dispersion_Strategy (void)
{
ACE_MT (ACE_GUARD (TAO_SYNCH_MUTEX,
guard,
this->lock_));
TAO_LB_ReplicaProxySetIterator begin = this->proxies_.begin ();
TAO_LB_ReplicaProxySetIterator end = this->proxies_.end ();
// @@ Bad deactivation!
for (TAO_LB_ReplicaProxySetIterator i = begin;
i != end;
++i)
{
// Decrease reference count on each proxy servant in the set.
(*i)->_remove_ref ();
}
}
CORBA::Object_ptr
TAO_LB_Minimum_Dispersion_Strategy::replica (TAO_ENV_SINGLE_ARG_DECL)
ACE_THROW_SPEC ((CORBA::SystemException))
{
for ( ; ; )
{
ACE_GUARD_RETURN (TAO_SYNCH_MUTEX,
guard,
this->lock_,
CORBA::Object::_nil ());
if (this->proxies_.is_empty ())
// @@ What do we do if the set is empty?
ACE_THROW_RETURN (CORBA::OBJECT_NOT_EXIST (),
CORBA::Object::_nil ());
TAO_LB_ReplicaProxySetIterator begin = this->proxies_.begin ();
TAO_LB_ReplicaProxySetIterator end = this->proxies_.end ();
TAO_LB_ReplicaProxySetIterator i = begin;
TAO_LB_ReplicaProxy * proxy = (*i);
float d = (*i)->current_load ();
for (++i ; i != end; ++i)
{
if (d > (*i)->current_load ())
{
proxy = *i;
d = (*i)->current_load ();
}
}
// Before returning an object reference to the client
// validate it first.
CORBA::Object_var object =
proxy->replica ();
{
ACE_Reverse_Lock<TAO_SYNCH_MUTEX> reverse_lock (this->lock_);
ACE_GUARD_RETURN (ACE_Reverse_Lock<TAO_SYNCH_MUTEX>,
reverse_guard,
reverse_lock,
CORBA::Object::_nil ());
// @@ Ossama: we should setup a timeout policy here...
ACE_TRY
{
CORBA::Boolean non_existent =
object->_non_existent (TAO_ENV_SINGLE_ARG_PARAMETER);
ACE_TRY_CHECK;
if (!non_existent)
{
return object._retn ();
}
}
ACE_CATCHANY
{
}
ACE_ENDTRY;
}
// @@ Ossama: a bit melodramatic, we remove the object if *any*
// exception is thrown. If the object really does not exist (we
// get non_existent==1) then this is exactly what we want to do,
// but if we get something like TRANSIENT we may want to do
// something less drastic, or at least strategize it ;-)
this->proxies_.remove (proxy);
}
}
int
TAO_LB_Minimum_Dispersion_Strategy::insert (TAO_LB_ReplicaProxy *proxy)
{
ACE_MT (ACE_GUARD_RETURN (TAO_SYNCH_MUTEX,
guard,
this->lock_,
-1));
return this->proxies_.insert (proxy);
}
int
TAO_LB_Minimum_Dispersion_Strategy::remove (TAO_LB_ReplicaProxy *proxy)
{
ACE_MT (ACE_GUARD_RETURN (TAO_SYNCH_MUTEX,
guard,
this->lock_,
-1));
return this->proxies_.remove (proxy);
}
void
TAO_LB_Minimum_Dispersion_Strategy::load_changed (TAO_LB_ReplicaProxy *proxy
TAO_ENV_ARG_DECL)
{
int send_load_advisory = 0;
{
ACE_MT (ACE_GUARD (TAO_SYNCH_MUTEX,
guard,
this->lock_));
if (this->proxies_.is_empty ())
return;
TAO_LB_ReplicaProxySetIterator begin = this->proxies_.begin ();
TAO_LB_ReplicaProxySetIterator end = this->proxies_.end ();
float s = 0;
CORBA::ULong n = 0;
TAO_LB_ReplicaProxySetIterator i = begin;
for (;i != end; ++i)
{
s += (*i)->current_load ();
n++;
}
float avg = (n == 0 ? s : s / n);
float cl = proxy->current_load ();
if (avg == 0)
return;
float relative_load = cl / avg;
// @@ Ossama: Make the 1.5 factor adjustable, it is how much
// dispersion we tolerate before starting to send advisories.
if (relative_load > 1 + 1.5F / n)
{
proxy->has_high_load_ = 1;
send_load_advisory = 2; // 2 == Send high load advisory
}
if (send_load_advisory == 1 && relative_load < 1 + 0.9F / n)
{
proxy->has_high_load_ = 0;
send_load_advisory = 1; // 1 == Send nominal load advisory
}
}
// @@ Ossama: no debug messages in production code, my fault....
// ACE_DEBUG ((LM_DEBUG, "Load[%x] %f %f %f\n",
// proxy, cl, avg, relative_load));
// @@ Ossama: Make the 1.5 factor adjustable, it is how much
// dispersion we tolerate before starting to send advisories.
if (send_load_advisory == 2)
{
proxy->control_->high_load_advisory (TAO_ENV_SINGLE_ARG_PARAMETER);
ACE_CHECK;
return; // We may not throw an exception, so explicitly return.
}
// @@ Ossama: notice that we wait until the load is signifcantly
// lower before sending the nominal load advisory, it does not
// matter that much because the replicas automatically restart after
// rejecting one client....
// @@ Ossama: make the 0.9 factor adjustable, at least at
// construction time...
if (send_load_advisory == 1)
{
proxy->control_->nominal_load_advisory (TAO_ENV_SINGLE_ARG_PARAMETER);
ACE_CHECK;
}
}
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