hu.mta.sztaki.lpds.cloud.simulator.iaas.vmscheduling
Class Scheduler

java.lang.Object
  hu.mta.sztaki.lpds.cloud.simulator.iaas.vmscheduling.Scheduler

Direct Known Subclasses:

FirstFitScheduler

public abstract class Scheduler
extends Object

The base class for all VM schedulers, provides the foundational logic and simplifies the implementation of VM schedulers by allowing them to mainly focus on their scheduling logic.

Author:

"Gabor Kecskemeti, Laboratory of Parallel and Distributed Systems, MTA SZTAKI (c) 2012"

Nested Class Summary

static interface

Scheduler.QueueingEvent Implementing this interface allows the implementor to receive events from the scheduler about cases when it believes the infrastructure is not sufficient for its needs.

Field Summary

protected VMManager.CapacityChangeEvent<ResourceConstraints>	freeCapacity This field represents the action to be done when some resources become free on one of the currently running PMs in the IaaS.
private AlterableResourceConstraints	freeResourcesSinceLastSchedule In this field the simulator maintains those recently freed up resources that could be allowing a new scheduling run
private ConstantConstraints	minimumSchedulerRequirement Here we keep an account of the amount of resources a particular scheduler would need before it would be able to schedule a new VM request
private ArrayList<PhysicalMachine>	orderedPMcache This field contains an automatically updated list of all machines in the parent IaaS.
protected IaaSService	parent The IaaS for which this VM scheduler manages the VM requests.
private int	pmCacheLen current length of the pm cache so we don't need to query its size all the time
static Comparator<PhysicalMachine>	pmComparator A PM comparator that offers inverse ordering of PMs if used during sort
protected PhysicalMachine.StateChangeListener	pmstateChanged This is the action that takes place when one of the PMs at the IaaS changes its state.
protected UnalterableConstraintsPropagator	publicTQ the public version of totalQueued that mirrors its contents but does not allow changes on it
protected List<QueueingData>	queue The queue of the scheduler.
private StateDependentEventHandler<Scheduler.QueueingEvent,Integer>	queueListenerManager the manager of those objects who shown interest in receiving queuing related event notifications
private AlterableResourceConstraints	totalQueued the amount of resources needed for fulfilling all VM requests in the queue

Constructor Summary

Scheduler(IaaSService parent)
The main constructor of all schedulers.

Method Summary

boolean	dropVMrequest(VirtualMachine vm) Cancels a VM request by dropping the corresponding queuing data from the scheduler's queue.
List<VirtualMachine>	getQueuedVMs() Prepares a list of all the VMs that are queued at the particular moment in time
int	getQueueLength() The number of VM requests queued at the moment
ResourceConstraints	getTotalQueued() The complete resource set required to fulfill the entirety of the VM requests in the queue
private void	invokeRealScheduler() This function is actually calling the subclass's scheduler implementation and handles the management of minimum scheduler requirements and resets the free resource aggregate
protected QueueingData	manageQueueRemoval() Removes the head of the queue
protected void	manageQueueRemoval(QueueingData qd) Removes an arbitrary item from the queue (could be a rather slow operation!)
protected abstract ConstantConstraints	scheduleQueued() When a new VM scheduler is created this is the function to be implemented.
void	scheduleVMrequest(VirtualMachine[] vms, ResourceConstraints rc, Repository vaSource, HashMap<String,Object> schedulingConstraints) The main entry point to the schedulers.
void	subscribeQueueingEvents(Scheduler.QueueingEvent e) Allows third parties to get notified if the scheduler is not satisfied with the current infrastructure (e.g.
void	unsubscribeQueueingEvents(Scheduler.QueueingEvent e) Cancels the notifications about queuing events
private void	updateTotalQueuedAfterRemoval(QueueingData qd) The common functionality required to manage the update of the total queued field.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

parent

protected final IaaSService parent

The IaaS for which this VM scheduler manages the VM requests.

queue

protected List<QueueingData> queue

The queue of the scheduler. This is intentionally made protected so subclasses could replace the list implementation to one that suits them better.

totalQueued

private AlterableResourceConstraints totalQueued

the amount of resources needed for fulfilling all VM requests in the queue

publicTQ

protected UnalterableConstraintsPropagator publicTQ

the public version of totalQueued that mirrors its contents but does not allow changes on it

orderedPMcache

private ArrayList<PhysicalMachine> orderedPMcache

This field contains an automatically updated list of all machines in the parent IaaS. The list is kept in the order of the PM's size to allow rapid decisions on the possible fitting of VM requests.

pmCacheLen

private int pmCacheLen

current length of the pm cache so we don't need to query its size all the time

queueListenerManager

private final StateDependentEventHandler<Scheduler.QueueingEvent,Integer> queueListenerManager

the manager of those objects who shown interest in receiving queuing related event notifications

minimumSchedulerRequirement

private ConstantConstraints minimumSchedulerRequirement

Here we keep an account of the amount of resources a particular scheduler would need before it would be able to schedule a new VM request

freeResourcesSinceLastSchedule

private AlterableResourceConstraints freeResourcesSinceLastSchedule

In this field the simulator maintains those recently freed up resources that could be allowing a new scheduling run

pmComparator

public static final Comparator<PhysicalMachine> pmComparator

A PM comparator that offers inverse ordering of PMs if used during sort

pmstateChanged

protected PhysicalMachine.StateChangeListener pmstateChanged

This is the action that takes place when one of the PMs at the IaaS changes its state. If this listener is called because a new PM has turned on then the scheduler is again given a chance to allocate some VMs. If there are some queued requests even after doing the scheduling then the queuelisteners are notified so they can improve the IaaS's infrastructure setup.

freeCapacity

protected VMManager.CapacityChangeEvent<ResourceConstraints> freeCapacity

This field represents the action to be done when some resources become free on one of the currently running PMs in the IaaS. If necessary this action invokes the scheduling and also notifies the queuing listeners about having a VM queue despite newly free resources.

Constructor Detail

Scheduler

public Scheduler(IaaSService parent)

The main constructor of all schedulers. This constructor ensures that the orderedPMcache is maintained and it also connects the scheduler's free capacity and pm state listeners.

Parameters:

parent - the IaaS service for which this scheduler is expected to act as the VM request scheduler

Method Detail

scheduleVMrequest

public final void scheduleVMrequest(VirtualMachine[] vms,
                                    ResourceConstraints rc,
                                    Repository vaSource,
                                    HashMap<String,Object> schedulingConstraints)
                             throws VMManager.VMManagementException

The main entry point to the schedulers. This function checks if a request could be possibly hosted on the IaaS's infrastructure, if so then it queues it. And if necessary it also invokes the actual scheduling operation implemented in the subclasses.

Parameters:

vms - the virtual machines that should be placed on the IaaS's machine set

rc - the resource requirements for the VMs

vaSource - the repository that stores the virtual appliance for the above VM set.

schedulingConstraints - custom data to be passed on to subclassed schedulers

Throws:

VMManager.VMManagementException - if the request is impossible to schedule on the current infrastructure

dropVMrequest

public final boolean dropVMrequest(VirtualMachine vm)

Cancels a VM request by dropping the corresponding queuing data from the scheduler's queue.

Parameters:

vm - the VM which is representing the queued request to be dropped from the queue

Returns:

true if the request was actually dropped, false otherwise.

getTotalQueued

public ResourceConstraints getTotalQueued()

The complete resource set required to fulfill the entirety of the VM requests in the queue

Returns:

the complete resource set

getQueueLength

public int getQueueLength()

The number of VM requests queued at the moment

Returns:

the length of the request queue

manageQueueRemoval

protected void manageQueueRemoval(QueueingData qd)

Removes an arbitrary item from the queue (could be a rather slow operation!)

Parameters:

qd - the item to be removed

manageQueueRemoval

protected QueueingData manageQueueRemoval()

Removes the head of the queue

Returns:

the queuing data object removed from the queue's head

updateTotalQueuedAfterRemoval

private void updateTotalQueuedAfterRemoval(QueueingData qd)

The common functionality required to manage the update of the total queued field.

Parameters:

qd - the removed queue member that needs to be deducted from the total queue field

subscribeQueueingEvents

public final void subscribeQueueingEvents(Scheduler.QueueingEvent e)

Allows third parties to get notified if the scheduler is not satisfied with the current infrastructure (e.g. because it cannot fit the current VM request set to the running PM set)

Parameters:

e - the object that will handle the notifications

unsubscribeQueueingEvents

public final void unsubscribeQueueingEvents(Scheduler.QueueingEvent e)

Cancels the notifications about queuing events

Parameters:

e - the object that no longer needs notifications

getQueuedVMs

public final List<VirtualMachine> getQueuedVMs()

Prepares a list of all the VMs that are queued at the particular moment in time

Returns:

the list of requested and not yet served VMs

invokeRealScheduler

private void invokeRealScheduler()

This function is actually calling the subclass's scheduler implementation and handles the management of minimum scheduler requirements and resets the free resource aggregate

scheduleQueued

protected abstract ConstantConstraints scheduleQueued()

When a new VM scheduler is created this is the function to be implemented. The function is expected to poll or the queue and only remove queued entities if they are placed on an actual PM. The removal is supported by the manageQueueRemoval function which allows both in order and out of order removals thus even allows prioritizing scheduler logic.

Returns:

the amount of free resources that the IaaS service needs to offer before this scheduler could actually proceed with its next VM placement.