给出一致性hash的代码
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentSkipListMap;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.stream.IntStream;
import lombok.extern.slf4j.Slf4j;
/**
* 带虚拟节点的一致性Hash算法
*/
@Slf4j
public class ShardHelper {
private ConcurrentSkipListMap<String, Set<Integer>> nodeHash = new ConcurrentSkipListMap<>();
private SortedMap<Integer, String> hashNode = new ConcurrentSkipListMap<>();
private static final int VIRTUAL_NODES = 32;
public synchronized void addRealNode(String name) {
for (int i = 0; i < VIRTUAL_NODES; i++) {
String virtualNodeName = name + "&&VN" + i;
int hash = getHash(virtualNodeName);
// log.info("{} {}", virtualNodeName, hash);
hashNode.put(hash, name);
nodeHash.computeIfAbsent(name, k -> ConcurrentHashMap.newKeySet())
.add(hash);
}
}
public synchronized void removeRealNode(String name) {
Set<Integer> hashes = nodeHash.remove(name);
for (Integer hash : hashes) {
hashNode.remove(hash);
}
}
//使用FNV1_32_HASH算法计算服务器的Hash值,这里不使用重写hashCode的方法,最终效果没区别
private int getHash(String str) {
// return Math.abs(str.hashCode());
final int p = 16777619;
int hash = (int) 2166136261L;
for (int i = 0; i < str.length(); i++)
hash = (hash ^ str.charAt(i)) * p;
hash += hash << 13;
hash ^= hash >> 7;
hash += hash << 3;
hash ^= hash >> 17;
hash += hash << 5;
// 如果算出来的值为负数则取其绝对值
if (hash < 0)
hash = Math.abs(hash);
return hash;
}
//得到应当路由到的结点
public String getServer(String key) {
//得到该key的hash值
int hash = getHash(key);
// 得到大于该Hash值的所有Map
SortedMap<Integer, String> subMap = hashNode.tailMap(hash);
String nodeName;
if (subMap.isEmpty()) {
//如果没有比该key的hash值大的,则从第一个node开始
Integer i = hashNode.firstKey();
//返回对应的服务器
nodeName = hashNode.get(i);
} else {
//第一个Key就是顺时针过去离node最近的那个结点
Integer i = subMap.firstKey();
//返回对应的服务器
nodeName = subMap.get(i);
}
return nodeName;
}
public static void main(String[] args) {
final ShardHelper shardHelper = new ShardHelper();
IntStream.range(1,100).forEach(
i->shardHelper.addRealNode(String.valueOf(i))
);
Map<String, AtomicInteger> counter=new HashMap<>();
for (int i = 0; i < 1000000; i++) {
final String server = shardHelper.getServer(String.valueOf(i));
counter.computeIfAbsent(String.valueOf(server),k->new AtomicInteger(0))
.incrementAndGet();
}
System.out.println(counter);
}
}