package com.fp;
import java.util.Collection;
import java.util.SortedMap;
import java.util.TreeMap;
public class ConsistentHash {
private final HashFunction hashFunction;
private final int numberOfReplicas;
private final SortedMap circle = new TreeMap();
public ConsistentHash(HashFunction hashFunction, int numberOfReplicas,
Collection nodes) {
this.hashFunction = hashFunction;
this.numberOfReplicas = numberOfReplicas;
for (ServerInfo node : nodes) {
add(node);
}
}
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);
}
}
public void remove(T node) {
for (int i = 0; i < numberOfReplicas; i++) {
circle.remove(hashFunction.hash(node.toString() + i));
}
}
public ServerInfo get(Object key) {
if (circle.isEmpty()) {
return null;
}
int hash = hashFunction.hash(key);
if (!circle.containsKey(hash)) {
SortedMap tailMap = circle.tailMap(hash);
hash = tailMap.isEmpty() ? circle.firstKey() : tailMap.firstKey();
}
return circle.get(hash);
}
static class HashFunction {
int hash(Object key) {
// md5åŠ å¯†åŽï¼Œhashcode
return MD5.md5(key.toString()).hashCode();
}
}
}