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/*
* CloudSim Plus: A modern, highly-extensible and easier-to-use Framework for
* Modeling and Simulation of Cloud Computing Infrastructures and Services.
* http://cloudsimplus.org
*
* Copyright (C) 2015-2018 Universidade da Beira Interior (UBI, Portugal) and
* the Instituto Federal de Educação Ciência e Tecnologia do Tocantins (IFTO, Brazil).
*
* This file is part of CloudSim Plus.
*
* CloudSim Plus is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* CloudSim Plus is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with CloudSim Plus. If not, see Since Cloudlets can be created and submitted to a broker in runtime,
* the number of arrived Cloudlets can be to much to existing VMs,
* requiring the creation of new VMs to balance the load.
* A HorizontalVmScaling implementation performs
* such up scaling by creating VMs as needed.
*
*
*
* To enable horizontal down scaling to destroy idle VMs, the {@link DatacenterBroker} has to be used
* by setting a {@link DatacenterBroker#getVmDestructionDelayFunction()}.
* Since there is no Cloudlet migration mechanism (and it isn't intended to have),
* if a VM becomes underloaded, there is nothing that can be done until all Cloudlets
* finish executing. When that happens, the {@link DatacenterBroker#getVmDestructionDelayFunction()}
* will handle such a situation.
*
*
* @author Manoel Campos da Silva Filho
* @since CloudSim Plus 1.0.0
*/
public interface HorizontalVmScaling extends VmScaling {
Predicate FALSE_PREDICATE = vm -> false;
/**
* An attribute that implements the Null Object Design Pattern for {@link HorizontalVmScaling}
* objects.
*/
HorizontalVmScaling NULL = new HorizontalVmScalingNull();
/**
* Gets a {@link Supplier} that will be used to create VMs when
* the Load Balancer detects that the current Broker's VMs are overloaded.
*
* @return
*/
Supplier getVmSupplier();
/**
* Sets a {@link Supplier} that will be used to create VMs when
* the Load Balancer detects that Broker's VMs are overloaded.
*
* @param supplier the supplier to set
* @return
*/
HorizontalVmScaling setVmSupplier(Supplier supplier);
/**
* Requests a horizontal scale if the Vm is overloaded, according to the {@link #getOverloadPredicate()} predicate.
* The scaling is performed by creating a new Vm using the {@link #getVmSupplier()} method
* and submitting it to the broker.
*
* The time interval in which it will be checked if the Vm is overloaded
* depends on the {@link Datacenter#getSchedulingInterval()} value.
* Make sure to set such a value to enable the periodic overload verification.
*
* The method will check the need to create a new
* VM at the time interval defined by the {@link Datacenter#getSchedulingInterval()}.
* A VM creation request is only sent when the VM is overloaded and
* new Cloudlets were submitted to the broker.
*
*
* @param evt current simulation time
* @return {@inheritDoc}
*/
@Override
boolean requestUpScalingIfPredicateMatches(VmHostEventInfo evt);
/**
* Gets a {@link Predicate} that defines when {@link #getVm() Vm} is overloaded or not,
* that will make the Vm's {@link DatacenterBroker} to up scale the VM.
* The up scaling is performed by creating new VMs to attend new arrived Cloudlets
* and then balance the load.
*
* @return
* @see #setOverloadPredicate(Predicate)
*/
Predicate getOverloadPredicate();
/**
* Sets a {@link Predicate} that defines when the {@link #getVm() Vm} is overloaded or not,
* making the {@link DatacenterBroker} to up scale the VM.
* The up scaling is performed by creating new VMs to attend new arrived Cloudlets
* in order to balance the load.
*
* @param predicate a predicate that checks certain conditions
* to define a {@link #getVm() Vm} as overloaded.
* The predicate receives the Vm that has to be checked.
* Such a condition can be defined, for instance,
* based on Vm's {@link Vm#getCpuPercentUsage(double)} CPU usage}
* and/or any other VM resource usage.
* Despite the VmScaling already is already linked to a {@link #getVm() Vm},
* the Vm parameter for the {@link Predicate} enables reusing the same predicate
* to detect overload of different VMs.
* @return
*/
VmScaling setOverloadPredicate(Predicate predicate);
}