import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;
public class MyConsistHash {
// 平均虚拟节点数
int NUM_REPS = 160;
HashAlgorithm alg = HashAlgorithm.KETAMA_HASH;
public static byte[] computeMD5(final String k) {
MessageDigest md5;
try {
md5 = MessageDigest.getInstance("MD5");
} catch (NoSuchAlgorithmException e) {
throw new RuntimeException("MD5 not supported", e);
}
md5.reset();
md5.update(k.getBytes());
return md5.digest();
}
public TreeMap<Long, String> buildMacMap(final List<String> macIps) {
final TreeMap<Long/* hash */, String/* macIp */> macMap = new TreeMap<Long, String>();
for (String ip : macIps) {
if (this.alg == HashAlgorithm.KETAMA_HASH) {
for (int i = 0; i < NUM_REPS / 4; i++) {
final byte[] digest = HashAlgorithm.computeMd5(ip + "-"
+ i);
for (int h = 0; h < 4; h++) {
final long k = (long) (digest[3 + h * 4] & 0xFF) << 24
| (long) (digest[2 + h * 4] & 0xFF) << 16
| (long) (digest[1 + h * 4] & 0xFF) << 8
| digest[h * 4] & 0xFF;
macMap.put(k, ip);
}
}
} else {
for (int i = 0; i < NUM_REPS; i++) {
final long key = this.alg.hash(ip + "-" + i);
macMap.put(key, ip);
}
}
}
return macMap;
}
public String findMacByKey(final TreeMap<Long, String> macMap, final String key) {
final Long hash = this.alg.hash(key);
Long target = hash;
if (!macMap.containsKey(hash)) {
target = macMap.ceilingKey(hash);
if (target == null && !macMap.isEmpty()) {
target = macMap.firstKey();
}
}
final String targetMac = macMap.get(target);
return targetMac;
}
public static void main(String[] args){
List<String> ips=new ArrayList<String>();
ips.add("10.232.0.2");
ips.add("10.232.0.3");
ips.add("10.232.0.4");
ips.add("10.232.0.5");
ips.add("10.232.0.6");
ips.add("10.232.0.27");
ips.add("10.232.0.28");
ips.add("10.232.0.68");
ips.add("10.232.0.97");
MyConsistHash hash=new MyConsistHash();
// hash.setNUM_REPS(1024);
// hash.setAlg(HashAlgorithm.CRC32_HASH);
TreeMap<Long,String> macMap=hash.buildMacMap(ips);
Map<String,Long> stat=new HashMap<String,Long>();
long start=System.currentTimeMillis();
for(int i=0;i<100000;i++){
String ip=hash.findMacByKey(macMap, "a"+i);
Long count=stat.get(ip);
if(count==null){
stat.put(ip, new Long(0));
}else{
stat.put(ip, count+1);
}
}
System.out.println(System.currentTimeMillis()-start);
for(Map.Entry<String,Long> entry:stat.entrySet()){
System.out.println("mac:"+entry.getKey()+" hits:"+entry.getValue());
}
}
public void setAlg(HashAlgorithm alg) {
this.alg = alg;
}
public void setNUM_REPS(int nUM_REPS) {
NUM_REPS = nUM_REPS;
}
}
使用默认KETAMA_HASH,
80个虚拟节点:254ms mac:10.232.0.28 hits:10079 mac:10.232.0.68 hits:9699 mac:10.232.0.2 hits:10621 mac:10.232.0.3 hits:9798 mac:10.232.0.4 hits:13422 mac:10.232.0.5 hits:10045 mac:10.232.0.27 hits:10871 mac:10.232.0.6 hits:14791 mac:10.232.0.97 hits:10665 160个虚拟节点:265ms mac:10.232.0.28 hits:12355 mac:10.232.0.68 hits:11182 mac:10.232.0.2 hits:11178 mac:10.232.0.3 hits:9750 mac:10.232.0.4 hits:12429 mac:10.232.0.5 hits:9641 mac:10.232.0.27 hits:10777 mac:10.232.0.6 hits:10610 mac:10.232.0.97 hits:12069 320个虚拟节点:249ms mac:10.232.0.28 hits:11466 mac:10.232.0.68 hits:10064 mac:10.232.0.2 hits:11004 mac:10.232.0.3 hits:10186 mac:10.232.0.4 hits:11570 mac:10.232.0.5 hits:10740 mac:10.232.0.27 hits:11249 mac:10.232.0.6 hits:11324 mac:10.232.0.97 hits:12388 640个虚拟节点:245ms mac:10.232.0.28 hits:10701 mac:10.232.0.68 hits:10978 mac:10.232.0.2 hits:11272 mac:10.232.0.3 hits:10566 mac:10.232.0.4 hits:11700 mac:10.232.0.5 hits:10512 mac:10.232.0.27 hits:11314 mac:10.232.0.6 hits:11541 mac:10.232.0.97 hits:11407 1024个虚拟节点:224 ms mac:10.232.0.28 hits:11196 mac:10.232.0.68 hits:11198 mac:10.232.0.2 hits:11063 mac:10.232.0.3 hits:10930 mac:10.232.0.4 hits:11623 mac:10.232.0.5 hits:10448 mac:10.232.0.27 hits:11289 mac:10.232.0.6 hits:11508 mac:10.232.0.97 hits:10736
使用1024个虚拟节点,
CRC32_HASH:120ms mac:10.232.0.28 hits:10668 mac:10.232.0.68 hits:13738 mac:10.232.0.2 hits:8805 mac:10.232.0.3 hits:10010 mac:10.232.0.4 hits:9525 mac:10.232.0.5 hits:10088 mac:10.232.0.6 hits:12162 mac:10.232.0.27 hits:10855 mac:10.232.0.97 hits:14140 KETAMA_HASH:227ms mac:10.232.0.28 hits:11196 mac:10.232.0.68 hits:11198 mac:10.232.0.2 hits:11063 mac:10.232.0.3 hits:10930 mac:10.232.0.4 hits:11623 mac:10.232.0.5 hits:10448 mac:10.232.0.27 hits:11289 mac:10.232.0.6 hits:11508 mac:10.232.0.97 hits:10736 MYSQL_HASH:82ms mac:10.232.0.28 hits:10119 mac:10.232.0.68 hits:13599 mac:10.232.0.2 hits:15329 mac:10.232.0.3 hits:16799 mac:10.232.0.4 hits:7199 mac:10.232.0.5 hits:10159 mac:10.232.0.27 hits:8519 mac:10.232.0.6 hits:3899 mac:10.232.0.97 hits:14369 ELECTION_HASH:243ms mac:10.232.0.28 hits:11054 mac:10.232.0.68 hits:10554 mac:10.232.0.2 hits:11180 mac:10.232.0.3 hits:11092 mac:10.232.0.4 hits:11137 mac:10.232.0.5 hits:11519 mac:10.232.0.27 hits:10753 mac:10.232.0.6 hits:11412 mac:10.232.0.97 hits:11290 LUA_HASH:113ms mac:10.232.0.28 hits:10950 mac:10.232.0.68 hits:11137 mac:10.232.0.2 hits:10783 mac:10.232.0.3 hits:11370 mac:10.232.0.4 hits:11143 mac:10.232.0.5 hits:10991 mac:10.232.0.27 hits:11645 mac:10.232.0.6 hits:11048 mac:10.232.0.97 hits:10924 NATIVE_HASH:81ms mac:10.232.0.68 hits:89999 mac:10.232.0.2 hits:9999 ...