一致性哈希算法 Java实现

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import java.util.*;
public class ConsistencyHash { 

private static final int VIRTUAL_MACHINE_NUMBER = 5 ;
private SortedMap<Integer,String> virtualNodeMap = new TreeMap<Integer, String>();
private  List<String> trueNodeList = new ArrayList<String>();
public void addNode(String node){ 

if(trueNodeList.contains(node)){ 

return;
}
trueNodeList.add(node);
for(int i=0;i<VIRTUAL_MACHINE_NUMBER;i++){ 

String virtualNodeName = node + i;
int hash = getHash(virtualNodeName);
virtualNodeMap.put(hash,virtualNodeName);
}
}
/** * 删除某个节点 * @param node */
public void delNode(String node){ 

trueNodeList.remove(node);
for(int i=0;i<VIRTUAL_MACHINE_NUMBER;i++){ 

String virtualNodeName = node + i;
int hash = getHash(virtualNodeName);
virtualNodeMap.remove(hash);
}
}
/** * FNV哈希算法 * @param key * @return */
public int getHash(String key){ 

int p = 16777619;
int hash = (int)2166136261L;
for(int i=0;i<key.length();i++){ 

hash=(hash^key.charAt(i))*p;
}
hash+=hash<<13;
hash^=hash>>7;
hash+=hash<<3;
hash^=hash>>17;
hash+=hash<<5;
return hash>0?hash:Math.abs(hash);
}
public String getServer(String key){ 

int hash = getHash(key);
SortedMap<Integer, String> tailMap = virtualNodeMap.tailMap(hash);
int nodeKey;
if(tailMap.isEmpty()){ 

nodeKey=virtualNodeMap.firstKey();
}else{ 

nodeKey=tailMap.firstKey();
}
String virtualNodeName = virtualNodeMap.get(nodeKey);
return virtualNodeName.substring(0,virtualNodeName.length()-1);
}
public static void main(String[] args) { 

ConsistencyHash consistencyHash = new ConsistencyHash();
String[] nodes = { 
"192.168.1.1","192.168.1.2","192.168.1.3"};
for(String node:nodes){ 

consistencyHash.addNode(node);
}
Map<String,List<Integer>> taskDistributionMap = new HashMap();
for(int i=0;i<100;i++){ 

String server = consistencyHash.getServer("abc"+i + "def" );
List<Integer> list = taskDistributionMap.get(server);
if(list==null){ 

list = new ArrayList<>();
taskDistributionMap.put(server,list);
}
list.add(i);
}
for(Map.Entry<String,List<Integer>> entry:taskDistributionMap.entrySet()){ 

System.out.print(entry.getKey()+" "+entry.getValue().size()+" tasks:");
for(int t:entry.getValue()){ 

System.out.print(t+" ");
}
System.out.println();
}
consistencyHash.addNode("192.168.1.4");
taskDistributionMap = new HashMap();
for(int i=0;i<100;i++){ 

String server = consistencyHash.getServer("abc"+i + "def" );
List<Integer> list = taskDistributionMap.get(server);
if(list==null){ 

list = new ArrayList<>();
taskDistributionMap.put(server,list);
}
list.add(i);
}
for(Map.Entry<String,List<Integer>> entry:taskDistributionMap.entrySet()){ 

System.out.print(entry.getKey()+" "+entry.getValue().size()+" tasks:");
for(int t:entry.getValue()){ 

System.out.print(t+" ");
}
System.out.println();
}
}
}