内容简介：一致性哈希一般用来做分布式缓存将各服务器的哈希值映射到一个圆环上(一般用0~2^32-1)，缓存寻址时，将缓存的键取哈希值放到圆环上，然后顺时针寻找第一个服务器节点，用找到的这个节点做缓存服务器有缓存服务器5台，缓存键30个，分别对每个缓存键在服务器上寻址
一致性哈希一般用来做分布式缓存
将各服务器的哈希值映射到一个圆环上(一般用0~2^32-1)，缓存寻址时，将缓存的键取哈希值放到圆环上，然后顺时针寻找第一个服务器节点，用找到的这个节点做缓存服务器
Java 示例
有缓存服务器5台，缓存键30个，分别对每个缓存键在服务器上寻址
Java代码
package bj;
import lombok.RequiredArgsConstructor;
import org.apache.commons.codec.digest.DigestUtils;
import org.junit.Test;
import java.nio.ByteBuffer;
import java.util.TreeSet;
import java.util.stream.IntStream;
/**
* Created by BaiJiFeiLong@gmail.com at 2018/12/6 下午2:11
*/
public class LinearHashingTest {
@RequiredArgsConstructor
static class Node implements Comparable<Node> {
private final String name;
long digest() {
byte[] digest = DigestUtils.md5(name);
return Integer.toUnsignedLong(ByteBuffer.wrap(digest, 0, 4).getInt());
}
@Override
public int compareTo(Node o) {
return Long.compare(this.digest(), o.digest());
}
@Override
public String toString() {
return String.format("Node(name=%s, digest=%d)", name, digest());
}
}
@Test
public void testAlpha() {
TreeSet<Node> set = new TreeSet<>();
for (int i : new int[]{1, 2, 3, 4, 5}) {
set.add(new Node("server" + i));
}
System.out.println("Server nodes:");
for (Node node : set) {
System.out.println(node);
}
System.out.println("Routing...");
IntStream.rangeClosed(1, 20).forEach(i -> {
long hash = new Node("key" + i).digest();
System.out.printf("key%d\t%d\t => %s\n", i, hash, route(set, hash));
});
IntStream.rangeClosed(1, 20).forEach(i -> {
set.add(new Node("key" + i));
});
System.out.println("All nodes:");
for (Node node : set) {
System.out.println(node);
}
}
private Node route(TreeSet<Node> nodes, long code) {
for (Node node : nodes) {
if (node.digest() > code) {
return node;
}
}
return nodes.first();
}
}
``
控制台输出:
```log
Node(name=server3, digest=232443701)
Node(name=server2, digest=424647047)
Node(name=server4, digest=648772546)
Node(name=server5, digest=1375127456)
Node(name=server1, digest=2822999463)
Routing...
key1 3266172564 => Node(name=server3, digest=232443701)
key2 2029528490 => Node(name=server1, digest=2822999463)
key3 909203333 => Node(name=server5, digest=1375127456)
key4 3405308747 => Node(name=server3, digest=232443701)
key5 1034591130 => Node(name=server5, digest=1375127456)
key6 1684928417 => Node(name=server1, digest=2822999463)
key7 4187051213 => Node(name=server3, digest=232443701)
key8 1564577213 => Node(name=server1, digest=2822999463)
key9 215402731 => Node(name=server3, digest=232443701)
key10 4045919512 => Node(name=server3, digest=232443701)
key11 3930184853 => Node(name=server3, digest=232443701)
key12 3610429654 => Node(name=server3, digest=232443701)
key13 4149020260 => Node(name=server3, digest=232443701)
key14 2302410740 => Node(name=server1, digest=2822999463)
key15 1605175883 => Node(name=server1, digest=2822999463)
key16 4248449615 => Node(name=server3, digest=232443701)
key17 3126975152 => Node(name=server3, digest=232443701)
key18 533962436 => Node(name=server4, digest=648772546)
key19 1425581655 => Node(name=server1, digest=2822999463)
key20 180948674 => Node(name=server3, digest=232443701)
All nodes:
Node(name=key20, digest=180948674)
Node(name=key9, digest=215402731)
Node(name=server3, digest=232443701)
Node(name=server2, digest=424647047)
Node(name=key18, digest=533962436)
Node(name=server4, digest=648772546)
Node(name=key3, digest=909203333)
Node(name=key5, digest=1034591130)
Node(name=server5, digest=1375127456)
Node(name=key19, digest=1425581655)
Node(name=key8, digest=1564577213)
Node(name=key15, digest=1605175883)
Node(name=key6, digest=1684928417)
Node(name=key2, digest=2029528490)
Node(name=key14, digest=2302410740)
Node(name=server1, digest=2822999463)
Node(name=key17, digest=3126975152)
Node(name=key1, digest=3266172564)
Node(name=key4, digest=3405308747)
Node(name=key12, digest=3610429654)
Node(name=key11, digest=3930184853)
Node(name=key10, digest=4045919512)
Node(name=key13, digest=4149020260)
Node(name=key7, digest=4187051213)
Node(name=key16, digest=4248449615)
以上所述就是小编给大家介绍的《哈希大杂烩》，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对 码农网 的支持！
猜你喜欢:
本站部分资源来源于网络，本站转载出于传递更多信息之目的，版权归原作者或者来源机构所有，如转载稿涉及版权问题，请联系我们。
Fluent Python
Luciano Ramalho / O'Reilly Media / 2015-8-20 / USD 39.99
Learn how to write idiomatic, effective Python code by leveraging its best features. Python's simplicity quickly lets you become productive with it, but this often means you aren’t using everything th......一起来看看 《Fluent Python》 这本书的介绍吧!
