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Copy pathConsistentHash.java
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57 lines (49 loc) · 1.64 KB
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package com.fp;
import java.util.Collection;
import java.util.SortedMap;
import java.util.TreeMap;
public class ConsistentHash<T> {
private final HashFunction hashFunction;//hash算法接口，需要实现
private final int numberOfReplicas;//虚拟节点因子
private final SortedMap<Integer, ServerInfo> circle = new TreeMap<Integer, ServerInfo>();//存储服务器的容器
//构造一致性算法实例，正常情况下，实际环境应该提供单例即可
public ConsistentHash(HashFunction hashFunction, int numberOfReplicas,
Collection<ServerInfo> nodes) {
this.hashFunction = hashFunction;
this.numberOfReplicas = numberOfReplicas;
for (ServerInfo node : nodes) {
add(node);
}
}
//添加虚拟节点
public void add(ServerInfo node) {
circle.put(hashFunction.hash(node.ip), node);
for (int i = 0; i < numberOfReplicas; i++) {
circle.put(hashFunction.hash(node.ip + i), node);
}
}
//删除某个物理机器所有的虚拟节点
public void remove(T node) {
for (int i = 0; i < numberOfReplicas; i++) {
circle.remove(hashFunction.hash(node.toString() + i));
}
}
//根据需要存储的数据的key获取顺时针方向最近的一个存储服务器
public ServerInfo get(Object key) {
if (circle.isEmpty()) {
return null;
}
int hash = hashFunction.hash(key);
if (!circle.containsKey(hash)) {
SortedMap<Integer, ServerInfo> tailMap = circle.tailMap(hash);
hash = tailMap.isEmpty() ? circle.firstKey() : tailMap.firstKey();
}
return circle.get(hash);
}
static class HashFunction {
int hash(Object key) {
// md5加密后，hashcode
return MD5.md5(key.toString()).hashCode();
}
}
}