/*************************************************************************
* Copyright 2009-2014 Eucalyptus Systems, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
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*
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* along with this program. If not, see http://www.gnu.org/licenses/.
*
* Please contact Eucalyptus Systems, Inc., 6755 Hollister Ave., Goleta
* CA 93117, USA or visit http://www.eucalyptus.com/licenses/ if you need
* additional information or have any questions.
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* and permission notice:
*
* Software License Agreement (BSD License)
*
* Copyright (c) 2008, Regents of the University of California
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************************************************************************/
package com.eucalyptus.compute.common.internal.util;
import com.eucalyptus.util.HasNaturalId;
import com.google.common.base.Predicate;
public interface Reference<T extends Reference<T, R>, R extends HasNaturalId> {
enum State implements Predicate<Reference<?,?>> {
UNKNOWN, FREE, PENDING, EXTANT, RELEASING;
@Override
public boolean apply( final Reference<?,?> reference ) {
return this == reference.getState( );
}
}
/**
* Request is in-flight on the network (not just in memory) and state updates should be
* disregarded until the in-flight request completes.
*
* Calling {@link Reference#set(R)} completes the allocation, while calling
* {@link Reference#teardown()} resets the state to that before the reference change.
*/
public T set( R referer ) throws ResourceAllocationException;
/**
* Request is in-flight on the network (not just in memory) and state updates should be
* disregarded until the in-flight request completes.
*
* Calling {@link Reference#set(R)} completes the allocation, while calling
* {@link Reference#teardown()} resets the state to that before the reference change.
*/
T allocate( ) throws ResourceAllocationException;
/**
* The procedure for gracefully releasing the resource is pending a submitted in-flight request.
* Potential references to stale state may exist and should be disregarded until in-flight
* requests complete.
*
* Calling {@link Reference#set(R)} completes releasing the allocation, while calling
* {@link Reference#clear()} resets the state to that before the reference change.
*/
T release( ) throws ResourceAllocationException;
/**
* Dependent external resource state has been cleared and the resource is ready for re-use.
* @return
*
* @throws ResourceAllocationException
*/
boolean teardown( ) throws ResourceAllocationException;
/**
* Attempt to recover a resource allocation -- e.g., after a system restart. Constraints must be
* enforced on valid initial state.
*
* @throws ResourceAllocationException
*/
T reclaim( R referer ) throws ResourceAllocationException;
/**
* Get the current state of the reference.
*
* @return The state
*/
State getState( );
}