oracle.kv.impl.topo.change.TopologyChangeTracker Maven / Gradle / Ivy
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/*-
* Copyright (C) 2011, 2018 Oracle and/or its affiliates. All rights reserved.
*
* This file was distributed by Oracle as part of a version of Oracle NoSQL
* Database made available at:
*
* http://www.oracle.com/technetwork/database/database-technologies/nosqldb/downloads/index.html
*
* Please see the LICENSE file included in the top-level directory of the
* appropriate version of Oracle NoSQL Database for a copy of the license and
* additional information.
*/
package oracle.kv.impl.topo.change;
import java.io.Serializable;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import oracle.kv.impl.metadata.Metadata;
import oracle.kv.impl.topo.ResourceId;
import oracle.kv.impl.topo.Topology;
import oracle.kv.impl.topo.Topology.Component;
import com.sleepycat.persist.model.Persistent;
/**
* Manages all changes associated with the Topology. The changes are maintained
* as a sequence of Add, Update, Remove log records. The changes are noted
* by the corresponding log methods which are required to be invoked in
* a logically consistent order. For example, a RepGroup must be added to the
* topology, before a RepNode belonging to it is added to the group.
*
* The Add and Remove records reference components that could potentially be in
* active use in the Topology.This is done to keep the in-memory representation
* of the Topology as compact as possible.
*/
@Persistent
public class TopologyChangeTracker implements Serializable {
private static final long serialVersionUID = 1L;
/* The topology associated with the changes. */
private Topology topology;
private int seqNum = Metadata.EMPTY_SEQUENCE_NUMBER;
/*
* The ordered list of changes, with the most recent change at the end of
* the list.
*/
private LinkedList changes;
public TopologyChangeTracker(Topology topology) {
this.topology = topology;
changes = new LinkedList();
}
@SuppressWarnings("unused")
private TopologyChangeTracker() {
}
/**
* Returns the first sequence number in the list of changes or -1
* if the change list is empty.
*/
public int getFirstChangeSeqNum() {
return (changes.size() == 0) ?
- 1 : changes.get(0).getSequenceNumber();
}
/**
* Returns the current sequence number.
*
* The sequence number is incremented with each logical change to the
* topology. For example, add a RG, add a RN, change an RN, etc. A Topology
* that is out of date, with an earlier sequence number, can be updated by
* applying the changes that it is missing, in sequence, up to the target
* sequence number.
*/
public int getSeqNum() {
return seqNum;
}
/* Methods used to log changes. */
public void logAdd(Component component) {
component.setSequenceNumber(++seqNum);
changes.add(new Add(seqNum, component));
}
public void logUpdate(Component newComponent) {
newComponent.setSequenceNumber(++seqNum);
changes.add(new Update(seqNum, newComponent));
}
public void logRemove(ResourceId resourceId) {
changes.add(new Remove(++seqNum, resourceId));
assert topology.get(resourceId) == null;
}
/**
* @see Topology#getChanges(int)
*/
public List getChanges(int startSeqNum) {
int minSeqNum = (changes.size() == 0) ? 0 :
changes.getFirst().sequenceNumber;
if (startSeqNum < minSeqNum) {
return null;
}
if (startSeqNum > changes.getLast().getSequenceNumber()) {
return null;
}
LinkedList copy = new LinkedList();
for (TopologyChange change : changes) {
if (change.getSequenceNumber() >= startSeqNum) {
copy.add(change.clone());
}
}
return copy;
}
/**
* @see Topology#getChanges(int)
*/
public List getChanges() {
return getChanges((changes.size() == 0) ? 0 :
changes.getFirst().sequenceNumber);
}
/**
* @see Topology#discardChanges(int)
*/
public void discardChanges(int startSeqNum) {
for (Iterator i = changes.iterator();
i.hasNext() && (i.next().getSequenceNumber() <= startSeqNum);) {
i.remove();
}
}
}