/*
* Galaxy
* Copyright (c) 2012-2014, Parallel Universe Software Co. All rights reserved.
*
* This program and the accompanying materials are dual-licensed under
* either the terms of the Eclipse Public License v1.0 as published by
* the Eclipse Foundation
*
* or (per the licensee's choosing)
*
* under the terms of the GNU Lesser General Public License version 3.0
* as published by the Free Software Foundation.
*/
package co.paralleluniverse.galaxy.cluster;
import co.paralleluniverse.galaxy.cluster.DistributedTree.Listener;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentSkipListMap;
import java.util.concurrent.CopyOnWriteArrayList;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Helps deal with a branch of a distributed tree, when we want to consider the nodes only when they have given sub-nodes ("required properties").
* <p>
* If the underlying nodes are ordered and the helper is constructed with the ordered option, the handlers are called in the order the main nodes
* (the branch's children) were originally created, not the order in which they've become "completed" (their required properties satisfied)! <b>Important:</b> Assumes that once required properties are
* set they are never removed or unset (set to null), though they can be changed.
*
* @author pron
*/
public abstract class DistributedBranchHelper {
private static final Logger LOG = LoggerFactory.getLogger(DistributedBranchHelper.class);
private final DistributedTree tree;
private final String branchRoot;
private final boolean ordered;
private final ConcurrentSkipListMap<String, Node> nodes = new ConcurrentSkipListMap<String, Node>();
private final List<Listener> listeners = new CopyOnWriteArrayList<Listener>();
private boolean doneInit = false;
public DistributedBranchHelper(DistributedTree tree, final String branchRoot, boolean ordered) {
if (!branchRoot.startsWith("/"))
throw new IllegalArgumentException("Branch root must start with a '/', but is " + branchRoot);
this.tree = tree;
this.branchRoot = branchRoot;
this.ordered = ordered;
tree.addListener(branchRoot, new Listener() {
@Override
public void nodeChildAdded(String node, String childName) {
assert node.equals(branchRoot);
DistributedBranchHelper.this.nodeAdded(childName);
}
@Override
public void nodeChildDeleted(String node, String childName) {
assert node.equals(branchRoot);
DistributedBranchHelper.this.nodeRemoved(childName);
}
@Override
public void nodeChildUpdated(String node, String childName) {
assert node.equals(branchRoot);
DistributedBranchHelper.this.nodeUpdated(childName);
}
@Override
public void nodeUpdated(String node) {
assert node.equals(branchRoot);
for (Listener listener : listeners)
listener.nodeUpdated(node);
}
@Override
public void nodeAdded(String node) {
assert node.equals(branchRoot);
for (Listener listener : listeners)
listener.nodeAdded(node);
}
@Override
public void nodeDeleted(String node) {
assert node.equals(branchRoot);
for (Listener listener : listeners)
listener.nodeDeleted(node);
}
});
}
public final void init() {
synchronized (nodes) {
if (ordered) {
final Node first = getFirstNode();
if (first != null)
first.predecessorsComplete();
}
doneInit = true;
nodes.notifyAll();
}
}
public void addListener(Listener listener) {
synchronized (nodes) {
for (Node node : nodes.values()) {
if (node.isComplete())
listener.nodeChildAdded(branchRoot, node.name);
else if (ordered)
break;
}
listeners.add(listener);
}
}
public void removeListener(Listener listener) {
listeners.remove(listener);
}
public List<String> getChildren() {
final List<String> children = new ArrayList<String>();
synchronized (nodes) {
for (Node node : nodes.values()) {
if (!node.isComplete())
break;
children.add(node.name);
}
}
return Collections.unmodifiableList(children);
}
private void nodeAdded(String name) {
synchronized (nodes) {
// by re-inserting existent nodes, we take care of race conditions between the handler and the getChildren call in the constructor
// we make sure that the order is that of getChildren
Node node = nodes.remove(name);
if (node == null)
node = new Node(name);
nodes.put(name, node);
LOG.debug("Node {} added.", name);
if (ordered) {
final Node previous = getPreviousNode(name);
if ((previous == null && doneInit) || (previous != null && previous.isComplete()))
node.predecessorsComplete();
}
}
}
private void nodeCompleted(String name) {
LOG.debug("Node {} completed", name);
for (Listener listener : listeners)
listener.nodeChildAdded(branchRoot, name);
if (ordered) {
synchronized (nodes) {
final Node next = getNextNode(name);
if (next != null)
next.predecessorsComplete(); // possibly sets off recursion
}
}
}
private void nodeUpdated(String name) {
try {
final Node node;
synchronized (nodes) {
while (!doneInit)
nodes.wait();
node = nodes.get(name);
}
assert node != null;
LOG.debug("Node {} updated. ({})", name, node.isComplete() ? "complete" : "incomplete");
if (node.isComplete()) {
for (Listener listener : listeners)
listener.nodeChildUpdated(branchRoot, name);
}
} catch (InterruptedException e) {
throw new RuntimeException();
}
}
private void nodeRemoved(String name) {
try {
boolean _doneInit;
final Node node;
Node previous = null, next = null;
synchronized (nodes) {
while (!doneInit)
nodes.wait();
if (ordered) {
previous = value(nodes.lowerEntry(name));
next = value(nodes.higherEntry(name));
}
node = nodes.remove(name);
_doneInit = this.doneInit;
}
if (node.isComplete()) {
for (Listener listener : listeners)
listener.nodeChildDeleted(branchRoot, name);
}
if (ordered) {
if (_doneInit && next != null && (previous == null || previous.isComplete()))
next.predecessorsComplete();
}
} catch (InterruptedException e) {
throw new RuntimeException();
}
}
private Node getNextNode(String node) {
assert ordered;
synchronized (nodes) {
final Map.Entry<String, Node> entry = nodes.higherEntry(node);
return (entry != null ? entry.getValue() : null);
}
}
private Node getPreviousNode(String node) {
assert ordered;
synchronized (nodes) {
final Map.Entry<String, Node> entry = nodes.lowerEntry(node);
return (entry != null ? entry.getValue() : null);
}
}
private Node getFirstNode() {
assert ordered;
synchronized (nodes) {
final Map.Entry<String, Node> entry = nodes.firstEntry();
return (entry != null ? entry.getValue() : null);
}
}
protected abstract boolean isNodeComplete(String node, Set<String> properties);
private class Node extends DistributedTree.ListenerAdapter {
final String name;
private final String treePath;
private final Set<String> properties = new HashSet<String>();
private boolean predecessorsComplete;
private boolean complete = false;
public Node(String name) {
this.name = name;
this.treePath = branchRoot + '/' + name;
this.predecessorsComplete = !ordered;
tree.addListener(treePath, this);
for (String property : tree.getChildren(treePath))
testProperty(property);
}
public synchronized boolean isComplete() {
return complete;
}
public void predecessorsComplete() {
assert ordered;
synchronized (this) {
if (predecessorsComplete)
return;
predecessorsComplete = true;
}
testComplete();
}
private void testProperty(String property) {
LOG.debug("Test property for {}: {}", name, property);
synchronized (this) {
if (tree.get(treePath + '/' + property) == null)
return;
properties.add(property);
}
testComplete();
}
private void testComplete() {
synchronized (this) {
if (complete)
return;
if (!predecessorsComplete || !isNodeComplete(treePath, properties))
return;
complete = true;
tree.removeListener(treePath, this);
LOG.debug("Node {} is now complete!", name);
}
nodeCompleted(name); // must be called outside the sync block because it syncs on nodes - might cause deadlock
}
@Override
public void nodeChildAdded(String node, String childName) {
nodeChildUpdated(node, childName); // possibly wasteful. consider.
}
@Override
public void nodeChildUpdated(String node, String childName) {
assert node.equals(treePath);
testProperty(childName);
}
}
private static <K, V> V value(Map.Entry<K, V> entry) {
return entry != null ? entry.getValue() : null;
}
private static <K, V> K key(Map.Entry<K, V> entry) {
return entry != null ? entry.getKey() : null;
}
}