第五周命题作业

// 服务器节点

public class Node {

private String domain;

private String ip;

private Map<String, Object> data;

public <T> void put(String key, T value) {

data.put(key, value);

}

public void remove(String key){

data.remove(key);

}

public <T> T get(String key) {

return (T) data.get(key);

}

}

// 服务器集群

public abstract class Cluster {

protected List<Node> nodes;

public Cluster() {

this.nodes = new ArrayList<>();

}

public abstract void addNode(Node node);

public abstract void removeNode(Node node);

public abstract Node get(String key);

}

// 一致性 hash（hash 环，虚拟节点）

public class ConsistencyHashCluster extends Cluster {

private SortedMap<Long, Node> virNodes = new TreeMap<Long, Node>();

private static final int VIRNODECOUNT = 512;

private static final String SPLIT = "#";

public ConsistencyHashCluster() {

super();

}

@Override

public void addNode(Node node) {

this.nodes.add(node);

IntStream.range(0, VIRNODECOUNT)

.forEach(index -> {

long hash = hash(node.getIp() + SPLIT + index);

virNodes.put(hash, node);

});

}

@Override

public void removeNode(Node node) {

nodes.removeIf(o -> node.getIp().equals(o.getIp()));

IntStream.range(0, VIRNODECOUNT)

.forEach(index -> {

long hash = hash(node.getIp() + SPLIT + index);

virNodes.remove(hash);

});

}

@Override

public Node get(String key) {

long hash = hash(key);

SortedMap<Long, Node> subMap = hash >= virNodes.lastKey() ? virNodes.tailMap(0L) : virNodes.tailMap(hash);

if (subMap.isEmpty()) {

return null;

}

return subMap.get(subMap.firstKey());

}

}