Redis Cluster的搭建與部署，實現redis的分布式方案

本文轉載自查看原文 2018-03-06 19:02 4230 大型網站技術架構/ cluster/ jedis/ 緩存/ redis

前言

　　上篇Redis Sentinel安裝與部署，實現redis的高可用實現了redis的高可用，針對的主要是master宕機的情況，我們發現所有節點的數據都是一樣的，那么一旦數據量過大，redis也會效率下降的問題。redis3.0版本正式推出后，有效地解決了Redis分布式方面的需求，當遇到單機內存、並發、流量等瓶頸時，可以采用Cluster架構方法達到負載均衡的目的。

　　而此篇將帶領大家實現Redis Cluster的搭建，並進行簡單的客戶端操作。

　　github地址：https://github.com/youzhibing/redis

環境准備　

　　redis版本：redis-3.0.0

　　linux：centos6.7

　　ip：192.168.11.202，不同的端口實現不同的redis實例

　　客戶端jedis，基於spring-boot

redis cluster環境搭建

節點准備

　　　　192.168.11.202:6382,192.168.11.202:6383,192.168.11.202:6384,192.168.11.202:6385,192.168.11.202:6386,192.168.11.202:6387搭建初始集群

　　　　192.168.11.202:6388，192.168.11.202:6389擴容時用到

　　　　redis-6382.conf

port 6382
bind 192.168.11.202
requirepass "myredis"
daemonize yes
logfile "6382.log"
dbfilename "dump-6382.rdb"
dir "/opt/soft/redis/cluster_data"

masterauth "myredis"
cluster-enabled yes
cluster-node-timeout 15000
cluster-config-file "nodes-6382.conf"

View Code

　　　　redis-6383.conf

port 6383
bind 192.168.11.202
requirepass "myredis"
daemonize yes
logfile "6383.log"
dbfilename "dump-6383.rdb"
dir "/opt/soft/redis/cluster_data"

masterauth "myredis"
cluster-enabled yes
cluster-node-timeout 15000
cluster-config-file "nodes-6383.conf"

View Code

　　　　redis-6384.conf

port 6384
bind 192.168.11.202
requirepass "myredis"
daemonize yes
logfile "6384.log"
dbfilename "dump-6384.rdb"
dir "/opt/soft/redis/cluster_data"

masterauth "myredis"
cluster-enabled yes
cluster-node-timeout 15000
cluster-config-file "nodes-6384.conf"

View Code

　　　　redis-6385.conf

port 6385
bind 192.168.11.202
requirepass "myredis"
daemonize yes
logfile "6385.log"
dbfilename "dump-6385.rdb"
dir "/opt/soft/redis/cluster_data"

masterauth "myredis"
cluster-enabled yes
cluster-node-timeout 15000
cluster-config-file "nodes-6385.conf"

View Code

　　　　redis-6386.conf

port 6386
bind 192.168.11.202
requirepass "myredis"
daemonize yes
logfile "6386.log"
dbfilename "dump-6386.rdb"
dir "/opt/soft/redis/cluster_data"

masterauth "myredis"
cluster-enabled yes
cluster-node-timeout 15000
cluster-config-file "nodes-6386.conf"

View Code

　　　　redis-6387.conf

port 6387
bind 192.168.11.202
requirepass "myredis"
daemonize yes
logfile "6387.log"
dbfilename "dump-6387.rdb"
dir "/opt/soft/redis/cluster_data"

masterauth "myredis"
cluster-enabled yes
cluster-node-timeout 15000
cluster-config-file "nodes-6387.conf"

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　　啟動全部節點

[root@slave1 redis_cluster]# cd /opt/redis-3.0.0/redis_cluster/
[root@slave1 redis_cluster]# ./../src/redis-server redis-6382.conf 
[root@slave1 redis_cluster]# ./../src/redis-server redis-6383.conf 
[root@slave1 redis_cluster]# ./../src/redis-server redis-6384.conf 
[root@slave1 redis_cluster]# ./../src/redis-server redis-6385.conf 
[root@slave1 redis_cluster]# ./../src/redis-server redis-6386.conf 
[root@slave1 redis_cluster]# ./../src/redis-server redis-6387.conf

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　　創建集群

　　　　節點全部啟動后，每個節點目前只能識別出自己的節點信息，彼此之間並不知道對方的存在；

　　　　采用redis-trib.rb來實現集群的快速搭建，redis-trib.rb是采用Rudy實現的集群管理工具，內部通過Cluster相關命令幫我們簡化集群創建、檢查、槽遷移和均衡等常見運維操作。

　　　　有興趣的朋友可以采用cluster 命令一步一步的手動實現redis cluster的搭建，就可以明白redis-trib.rb是如何快速實現redis cluster的搭建的。

　　　　搭建命令如下，其中--replicas 1表示每個主節點配置1個從節點

[root@slave1 src]# cd /opt/redis-3.0.0/src/
[root@slave1 src]# ./redis-trib.rb create --replicas 1 192.168.11.202:6382 192.168.11.202:6383 192.168.11.202:6384 192.168.11.202:6385 192.168.11.202:6386 192.168.11.202:6387

　　　　創建過程中會給出主從節點角色分配的計划，如下所示

>>> Creating cluster
Connecting to node 192.168.11.202:6382: OK
Connecting to node 192.168.11.202:6383: OK
Connecting to node 192.168.11.202:6384: OK
Connecting to node 192.168.11.202:6385: OK
Connecting to node 192.168.11.202:6386: OK
Connecting to node 192.168.11.202:6387: OK
>>> Performing hash slots allocation on 6 nodes...
Using 3 masters:
192.168.11.202:6382
192.168.11.202:6383
192.168.11.202:6384
Adding replica 192.168.11.202:6385 to 192.168.11.202:6382
Adding replica 192.168.11.202:6386 to 192.168.11.202:6383
Adding replica 192.168.11.202:6387 to 192.168.11.202:6384
M: 0ec055f9daa5b4f570e6a4c4d46e5285d16e0afe 192.168.11.202:6382
   slots:0-5460 (5461 slots) master
M: 3771e67edab547deff6bd290e1a07b23646906ee 192.168.11.202:6383
   slots:5461-10922 (5462 slots) master
M: 10b3789bb30889b5e6f67175620feddcd496d19e 192.168.11.202:6384
   slots:10923-16383 (5461 slots) master
S: 7649466ec006e0902a7f1578417247a6d5540c47 192.168.11.202:6385
   replicates 0ec055f9daa5b4f570e6a4c4d46e5285d16e0afe
S: 4f36b08d8067a003af45dbe96a5363f348643509 192.168.11.202:6386
   replicates 3771e67edab547deff6bd290e1a07b23646906ee
S: a583def1e6a059e4fdb3592557fd6ab691fd61ec 192.168.11.202:6387
   replicates 10b3789bb30889b5e6f67175620feddcd496d19e
Can I set the above configuration? (type 'yes' to accept):

　　　　為什么192.168.11.202:6382 192.168.11.202:6383 192.168.11.202:6384是主節點，請看注意點中第1點；當我們同意這份計划之后，輸入yes，redis-trib.rb開始執行節點握手和槽分配操作，輸出如下

>>> Nodes configuration updated
>>> Assign a different config epoch to each node
>>> Sending CLUSTER MEET messages to join the cluster
Waiting for the cluster to join...
>>> Performing Cluster Check (using node 192.168.11.202:6382)
M: 0ec055f9daa5b4f570e6a4c4d46e5285d16e0afe 192.168.11.202:6382
   slots:0-5460 (5461 slots) master
M: 3771e67edab547deff6bd290e1a07b23646906ee 192.168.11.202:6383
   slots:5461-10922 (5462 slots) master
M: 10b3789bb30889b5e6f67175620feddcd496d19e 192.168.11.202:6384
   slots:10923-16383 (5461 slots) master
M: 7649466ec006e0902a7f1578417247a6d5540c47 192.168.11.202:6385
   slots: (0 slots) master
   replicates 0ec055f9daa5b4f570e6a4c4d46e5285d16e0afe
M: 4f36b08d8067a003af45dbe96a5363f348643509 192.168.11.202:6386
   slots: (0 slots) master
   replicates 3771e67edab547deff6bd290e1a07b23646906ee
M: a583def1e6a059e4fdb3592557fd6ab691fd61ec 192.168.11.202:6387
   slots: (0 slots) master
   replicates 10b3789bb30889b5e6f67175620feddcd496d19e
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.

　　　　16384個槽全部被分配，集群創建成功。

　　集群完整性檢查

　　　　redis-trib.rb check命令可以完成檢查工作，check命令只需給出集群中任意一個節點地址就可以完成整個集群的檢查工作，如下

　　　　redis-trib.rb check 192.168.11.202:6382，輸出結果如下

Connecting to node 192.168.11.202:6382: OK
Connecting to node 192.168.11.202:6385: OK
Connecting to node 192.168.11.202:6383: OK
Connecting to node 192.168.11.202:6384: OK
Connecting to node 192.168.11.202:6387: OK
Connecting to node 192.168.11.202:6386: OK
>>> Performing Cluster Check (using node 192.168.11.202:6382)
M: 0ec055f9daa5b4f570e6a4c4d46e5285d16e0afe 192.168.11.202:6382
   slots:0-5460 (5461 slots) master
   1 additional replica(s)
S: 7649466ec006e0902a7f1578417247a6d5540c47 192.168.11.202:6385
   slots: (0 slots) slave
   replicates 0ec055f9daa5b4f570e6a4c4d46e5285d16e0afe
M: 3771e67edab547deff6bd290e1a07b23646906ee 192.168.11.202:6383
   slots:5461-10922 (5462 slots) master
   1 additional replica(s)
M: 10b3789bb30889b5e6f67175620feddcd496d19e 192.168.11.202:6384
   slots:10923-16383 (5461 slots) master
   1 additional replica(s)
S: a583def1e6a059e4fdb3592557fd6ab691fd61ec 192.168.11.202:6387
   slots: (0 slots) slave
   replicates 10b3789bb30889b5e6f67175620feddcd496d19e
S: 4f36b08d8067a003af45dbe96a5363f348643509 192.168.11.202:6386
   slots: (0 slots) slave
   replicates 3771e67edab547deff6bd290e1a07b23646906ee
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.

View Code

　　　　[OK] All 16384 slots covered.表示集群所有的槽都已分配到節點。

　　　　引入了槽之后，整個數據流向如下圖所示：

　　　　至於為什么引入槽，請看注意點中第3點

　　redis cluster簡單操作

　　　　連接集群，隨便連接某個節點都可以；-c 集群支持，支持自動重定向

　　　　[root@slave1 redis_cluster]# ./../src/redis-cli -h 192.168.11.202 -p 6382 -a myredis -c

　　　　連接上redis cluster后就可以執行相關redis命令了，如下

192.168.11.202:6382> get name
-> Redirected to slot [5798] located at 192.168.11.202:6388
"youzhibing"
192.168.11.202:6388> set weight 112
-> Redirected to slot [16280] located at 192.168.11.202:6384
OK
192.168.11.202:6384> get weight
"112"
192.168.11.202:6384>

客戶端（Jedis）連接與操作

　　redis-cluster.properties

#cluster
redis.cluster.host=192.168.11.202
redis.cluster.port=6382,6383,6384,6385,6386,6387
#redis讀寫超時時間（毫秒）
redis.cluster.socketTimeout=1000
#redis連接超時時間（毫秒）
redis.cluster.connectionTimeOut=3000
#最大嘗試連接次數
redis.cluster.maxAttempts=10
#最大重定向次數
redis.cluster.maxRedirects=5
#master連接密碼
redis.password=myredis

# 連接池
# 連接池最大連接數（使用負值表示沒有限制）
redis.pool.maxActive=150
# 連接池中的最大空閑連接
redis.pool.maxIdle=10
# 連接池中的最小空閑連接
redis.pool.minIdle=1
# 獲取連接時的最大等待毫秒數,小於零:阻塞不確定的時間,默認-1
redis.pool.maxWaitMillis=3000
# 每次釋放連接的最大數目
redis.pool.numTestsPerEvictionRun=50
# 釋放連接的掃描間隔（毫秒）
redis.pool.timeBetweenEvictionRunsMillis=3000
# 連接最小空閑時間（毫秒）
redis.pool.minEvictableIdleTimeMillis=1800000
# 連接空閑多久后釋放, 當空閑時間>該值 且 空閑連接>最大空閑連接數 時直接釋放（毫秒）
redis.pool.softMinEvictableIdleTimeMillis=10000
# 在獲取連接的時候檢查有效性, 默認false
redis.pool.testOnBorrow=true
# 在空閑時檢查有效性, 默認false
redis.pool.testWhileIdle=true
# 在歸還給pool時，是否提前進行validate操作
redis.pool.testOnReturn=true
# 連接耗盡時是否阻塞, false報異常,ture阻塞直到超時, 默認true
redis.pool.blockWhenExhausted=true

View Code

　　RedisClusterConfig.java

package com.lee.redis.config.cluster;

import java.util.HashSet;
import java.util.Set;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.util.StringUtils;

import redis.clients.jedis.HostAndPort;
import redis.clients.jedis.JedisCluster;
import redis.clients.jedis.JedisPoolConfig;

import com.alibaba.fastjson.JSON;
import com.lee.redis.exception.LocalException;

@Configuration
@PropertySource("redis/redis-cluster.properties")
public class RedisClusterConfig {

    private static final Logger LOGGER = LoggerFactory.getLogger(RedisClusterConfig.class);
    
    // pool
    @Value("${redis.pool.maxActive}")
    private int maxTotal;
    @Value("${redis.pool.maxIdle}")
    private int maxIdle;
    @Value("${redis.pool.minIdle}")
    private int minIdle;
    @Value("${redis.pool.maxWaitMillis}")
    private long maxWaitMillis;
    @Value("${redis.pool.numTestsPerEvictionRun}")
    private int numTestsPerEvictionRun;
    @Value("${redis.pool.timeBetweenEvictionRunsMillis}")
    private long timeBetweenEvictionRunsMillis;
    @Value("${redis.pool.minEvictableIdleTimeMillis}")
    private long minEvictableIdleTimeMillis;
    @Value("${redis.pool.softMinEvictableIdleTimeMillis}")
    private long softMinEvictableIdleTimeMillis;
    @Value("${redis.pool.testOnBorrow}")
    private boolean testOnBorrow;
    @Value("${redis.pool.testWhileIdle}")
    private boolean testWhileIdle;
    @Value("${redis.pool.testOnReturn}")
    private boolean testOnReturn;
    @Value("${redis.pool.blockWhenExhausted}")
    private boolean blockWhenExhausted;
    
    // cluster
    @Value("${redis.cluster.host}")
    private String host;
    @Value("${redis.cluster.port}")
    private String port;
    @Value("${redis.cluster.socketTimeout}")
    private int socketTimeout;
    @Value("${redis.cluster.connectionTimeOut}")
    private int connectionTimeOut;
    @Value("${redis.cluster.maxAttempts}")
    private int maxAttempts;
    @Value("${redis.cluster.maxRedirects}")
    private int maxRedirects;
    @Value("${redis.password}")
    private String password;
    
    @Bean
    public JedisPoolConfig jedisPoolConfig() {
        JedisPoolConfig jedisPoolConfig = new JedisPoolConfig();
        jedisPoolConfig.setMaxTotal(maxTotal);
        jedisPoolConfig.setMaxIdle(maxIdle);
        jedisPoolConfig.setMinIdle(minIdle);
        jedisPoolConfig.setMaxWaitMillis(maxWaitMillis);
        jedisPoolConfig.setNumTestsPerEvictionRun(numTestsPerEvictionRun);
        jedisPoolConfig
                .setTimeBetweenEvictionRunsMillis(timeBetweenEvictionRunsMillis);
        jedisPoolConfig
                .setMinEvictableIdleTimeMillis(minEvictableIdleTimeMillis);
        jedisPoolConfig
                .setSoftMinEvictableIdleTimeMillis(softMinEvictableIdleTimeMillis);
        jedisPoolConfig.setTestOnBorrow(testOnBorrow);
        jedisPoolConfig.setTestWhileIdle(testWhileIdle);
        jedisPoolConfig.setTestOnReturn(testOnReturn);
        jedisPoolConfig.setBlockWhenExhausted(blockWhenExhausted);

        return jedisPoolConfig;
    }
    
    @Bean
    public JedisCluster jedisCluster(JedisPoolConfig jedisPoolConfig) {
        
        if (StringUtils.isEmpty(host)) {
            LOGGER.info("redis集群主機未配置");
            throw new LocalException("redis集群主機未配置");
        }
        if (StringUtils.isEmpty(port)) {
            LOGGER.info("redis集群端口未配置");
            throw new LocalException("redis集群端口未配置");
        }
        String[] hosts = host.split(",");
        String[] portArray = port.split(";");
        if (hosts.length != portArray.length) {
            LOGGER.info("redis集群主機數與端口數不匹配");
            throw new LocalException("redis集群主機數與端口數不匹配");
        }
        Set<HostAndPort> redisNodes = new HashSet<HostAndPort>();
        for (int i = 0; i < hosts.length; i++) {
            String ports = portArray[i];
            String[] hostPorts = ports.split(",");
            for (String port : hostPorts) {
                HostAndPort node = new HostAndPort(hosts[i], Integer.parseInt(port));
                redisNodes.add(node);
            }
        }
        LOGGER.info("Set<RedisNode> : {}", JSON.toJSONString(redisNodes), true);
        
        return new JedisCluster(redisNodes, connectionTimeOut, socketTimeout, maxAttempts, password, jedisPoolConfig);
    }
}

View Code

　　ApplicationCluster.java

package com.lee.redis;

import org.springframework.boot.Banner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
@EnableAutoConfiguration
@ComponentScan(basePackages={"com.lee.redis.config.cluster"})
public class ApplicationCluster {
    public static void main(String[] args) {
        
        SpringApplication app = new SpringApplication(ApplicationCluster.class);
        app.setBannerMode(Banner.Mode.OFF);            // 是否打印banner
        // app.setApplicationContextClass();        // 指定spring應用上下文啟動類
        app.setWebEnvironment(false);
        app.run(args);
    }
}

View Code

　　RedisClusterTest.java

package com.lee.redis;

import java.util.List;
import java.util.Map;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;

import com.alibaba.fastjson.JSON;

import redis.clients.jedis.JedisCluster;
import redis.clients.jedis.JedisPool;

@RunWith(SpringRunner.class)
@SpringBootTest(classes = ApplicationCluster.class)
public class RedisClusterTest {
    private static final Logger LOGGER = LoggerFactory.getLogger(RedisClusterTest.class);
    
    @Autowired
    private JedisCluster jedisCluster;
    
    @Test
    public void initTest() {
        String name = jedisCluster.get("name");
        LOGGER.info("name is {}", name);
        
        // list操作
        long count = jedisCluster.lpush("list:names", "陳芸");    // lpush的返回值是在 push操作后的 list 長度
        LOGGER.info("count = {}", count);
        long nameLen = jedisCluster.llen("list:names");
        LOGGER.info("list:names lens is {}", nameLen);
        List<String> nameList = jedisCluster.lrange("list:names", 0, nameLen);
        LOGGER.info("names : {}", JSON.toJSONString(nameList));
    }
}

View Code

　　執行RedisClusterTest.java中的initTest方法，結果如下

......
2018-03-06 09:56:05|INFO|com.lee.redis.RedisClusterTest|name is youzhibing
2018-03-06 09:56:05|INFO|com.lee.redis.RedisClusterTest|count = 3
2018-03-06 09:56:05|INFO|com.lee.redis.RedisClusterTest|list:names lens is 3
2018-03-06 09:56:05|INFO|com.lee.redis.RedisClusterTest|names : ["陳芸","沈復","沈復"]
......

集群的伸縮與故障轉移

　　cluster擴容

　　　　新增節點：192.168.11.202:6388, 192.168.11.202:6389，配置文件與之前的基本一致

　　　　　　redis-6388.conf

port 6388
bind 192.168.11.202
requirepass "myredis"
daemonize yes
logfile "6388.log"
dbfilename "dump-6388.rdb"
dir "/opt/soft/redis/cluster_data"

masterauth "myredis"
cluster-enabled yes
cluster-node-timeout 15000
cluster-config-file "nodes-6388.conf"

View Code

　　　　　　redis-6389.conf

port 6389
bind 192.168.11.202
requirepass "myredis"
daemonize yes
logfile "6389.log"
dbfilename "dump-6389.rdb"
dir "/opt/soft/redis/cluster_data"

masterauth "myredis"
cluster-enabled yes
cluster-node-timeout 15000
cluster-config-file "nodes-6389.conf"

View Code

　　　　　　啟動6388、6389節點

[root@slave1 redis_cluster]# cd /opt/redis-3.0.0/redis_cluster/
[root@slave1 redis_cluster]# ./../src/redis-server redis-6388.conf 
[root@slave1 redis_cluster]# ./../src/redis-server redis-6389.conf

View Code

　　　　加入集群：

[root@slave1 redis_cluster]# ./../src/redis-trib.rb add-node 192.168.11.202:6388 192.168.11.202:6382
#將6389添加成6388的從節點
[root@slave1 redis_cluster]# ./../src/redis-trib.rb add-node --slave --master-id e073db09e7aaed3c20d133726a26c8994932262c 192.168.11.202:6389 192.168.11.202:6382

　　遷移槽和數據

　　　　　　采用redis-trib-rb reshard命令執行槽重分片：[root@slave1 redis_cluster]# ./../src/redis-trib.rb reshard 192.168.11.202:6382

　　　　　　當出現 How many slots do you want to move (from 1 to 16384)? 提示我們想移動多少個槽，我們輸入4096

　　　　　　當出現What is the receiving node ID? 提示我們哪個主節點接收新移動的槽，我們輸入6388的節點id：e073db09e7aaed3c20d133726a26c8994932262c，目標節點只能指定一個（節點id可以拷貝的哦）

　　　　　　之后輸入源節點的id，用done結束，這里我用的all，就是從之前的全部主節點中移動4096個槽到6388

　　　　　　數據遷移之前會打印出所有的槽從源節點到目標節點的計划，確認無誤后輸入yes執行遷移工作

　　　　　　若遷移過程沒有出錯，那么遷移則順利完成

　　cluster故障轉移

　　　　6388上的所有key

192.168.11.202:6388> keys *
1) "list:names"
2) "name"
192.168.11.202:6388>

　　　　殺掉6388進程

[root@slave1 redis_cluster]# ps -ef | grep redis-server | grep 6388
root      8280     1  0 Mar05 ?        00:05:07 ./../src/redis-server 192.168.11.202:6388 [cluster]
[root@slave1 redis_cluster]# kill -9 8280

#集群節點查看
[root@slave1 redis_cluster]# ./../src/redis-cli -h 192.168.11.202 -p 6382 -a myredis -c
192.168.11.202:6382> cluster nodes
4f36b08d8067a003af45dbe96a5363f348643509 192.168.11.202:6386 slave 3771e67edab547deff6bd290e1a07b23646906ee 0 1520304517911 5 connected
0ec055f9daa5b4f570e6a4c4d46e5285d16e0afe 192.168.11.202:6382 myself,master - 0 0 1 connected 1394-5460
a583def1e6a059e4fdb3592557fd6ab691fd61ec 192.168.11.202:6387 slave 10b3789bb30889b5e6f67175620feddcd496d19e 0 1520304514886 6 connected
10b3789bb30889b5e6f67175620feddcd496d19e 192.168.11.202:6384 master - 0 1520304516904 3 connected 12318-16383
3771e67edab547deff6bd290e1a07b23646906ee 192.168.11.202:6383 master - 0 1520304513879 2 connected 7106-10922
e073db09e7aaed3c20d133726a26c8994932262c 192.168.11.202:6388 master,fail - 1520304485678 1520304484473 10 disconnected 0-1393 5461-7105 10923-12317
37de0d2dc1c267760156d4230502fa96a6bba64d 192.168.11.202:6389 slave e073db09e7aaed3c20d133726a26c8994932262c 0 1520304515895 10 connected
7649466ec006e0902a7f1578417247a6d5540c47 192.168.11.202:6385 slave 0ec055f9daa5b4f570e6a4c4d46e5285d16e0afe 0 1520304518923 4 connected
192.168.11.202:6382> 

#查詢key name
192.168.11.202:6382> get name
-> Redirected to slot [5798] located at 192.168.11.202:6389
"youzhibing"
192.168.11.202:6389> keys *
1) "list:names"
2) "name"
192.168.11.202:6389>

　　　　　　6389已經成為主節點，承擔着之前6388的角色，集群狀態還是ok的，對外提供的服務不受任何影響

　　　　重新啟動6388服務

[root@slave1 redis_cluster]# ./../src/redis-server redis-6388.conf

#查看集群節點
192.168.11.202:6389> cluster nodes
0ec055f9daa5b4f570e6a4c4d46e5285d16e0afe 192.168.11.202:6382 master - 0 1520304789567 1 connected 1394-5460
37de0d2dc1c267760156d4230502fa96a6bba64d 192.168.11.202:6389 myself,master - 0 0 12 connected 0-1393 5461-7105 10923-12317
7649466ec006e0902a7f1578417247a6d5540c47 192.168.11.202:6385 slave 0ec055f9daa5b4f570e6a4c4d46e5285d16e0afe 0 1520304788061 1 connected
a583def1e6a059e4fdb3592557fd6ab691fd61ec 192.168.11.202:6387 slave 10b3789bb30889b5e6f67175620feddcd496d19e 0 1520304787556 3 connected
3771e67edab547deff6bd290e1a07b23646906ee 192.168.11.202:6383 master - 0 1520304786550 2 connected 7106-10922
e073db09e7aaed3c20d133726a26c8994932262c 192.168.11.202:6388 slave 37de0d2dc1c267760156d4230502fa96a6bba64d 0 1520304786047 12 connected
10b3789bb30889b5e6f67175620feddcd496d19e 192.168.11.202:6384 master - 0 1520304785542 3 connected 12318-16383
4f36b08d8067a003af45dbe96a5363f348643509 192.168.11.202:6386 slave 3771e67edab547deff6bd290e1a07b23646906ee 0 1520304788561 2 connected
192.168.11.202:6389>

　　　　可以看到6388啟動成功后，仍在集群中，只是是作為6389的從節點了

　　cluster收縮

　　　　1、我們下線6389和6388節點

　　　　通過集群節點信息我們知道6389負責槽：0-1393 5461-7105 10923-12317，現在將0-1393遷移到6382，5461-7105遷移到6383， 10923-12317遷移到6384

How many slots do you want to move (from 1 to 16384)?1394
What is the receiving node ID? 0ec055f9daa5b4f570e6a4c4d46e5285d16e0afe
Please enter all the source node IDs.
  Type 'all' to use all the nodes as source nodes for the hash slots.
  Type 'done' once you entered all the source nodes IDs.
Source node #1:37de0d2dc1c267760156d4230502fa96a6bba64d
Source node #2:done
......
Do you want to proceed with the proposed reshard plan (yes/no)? yes


How many slots do you want to move (from 1 to 16384)? 1645
What is the receiving node ID? 3771e67edab547deff6bd290e1a07b23646906ee
Please enter all the source node IDs.
  Type 'all' to use all the nodes as source nodes for the hash slots.
  Type 'done' once you entered all the source nodes IDs.
Source node #1:37de0d2dc1c267760156d4230502fa96a6bba64d
Source node #2:done
......
Do you want to proceed with the proposed reshard plan (yes/no)? yes


How many slots do you want to move (from 1 to 16384)?1395
What is the receiving node ID? 10b3789bb30889b5e6f67175620feddcd496d19e
Please enter all the source node IDs.
  Type 'all' to use all the nodes as source nodes for the hash slots.
  Type 'done' once you entered all the source nodes IDs.
Source node #1:37de0d2dc1c267760156d4230502fa96a6bba64d
Source node #2:done
......
Do you want to proceed with the proposed reshard plan (yes/no)? yes

View Code

　　　　槽節點遷移完之后，集群節點信息，發現6388已經沒有分配槽了

192.168.11.202:6382> cluster nodes
3771e67edab547deff6bd290e1a07b23646906ee 192.168.11.202:6383 master - 0 1520333368013 16 connected 5461-10922
0ec055f9daa5b4f570e6a4c4d46e5285d16e0afe 192.168.11.202:6382 myself,master - 0 0 13 connected 0-5460
10b3789bb30889b5e6f67175620feddcd496d19e 192.168.11.202:6384 master - 0 1520333372037 17 connected 10923-16383
4f36b08d8067a003af45dbe96a5363f348643509 192.168.11.202:6386 slave 3771e67edab547deff6bd290e1a07b23646906ee 0 1520333370024 16 connected
a583def1e6a059e4fdb3592557fd6ab691fd61ec 192.168.11.202:6387 slave 10b3789bb30889b5e6f67175620feddcd496d19e 0 1520333370525 17 connected
37de0d2dc1c267760156d4230502fa96a6bba64d 192.168.11.202:6389 slave e073db09e7aaed3c20d133726a26c8994932262c 0 1520333369017 15 connected
7649466ec006e0902a7f1578417247a6d5540c47 192.168.11.202:6385 slave 0ec055f9daa5b4f570e6a4c4d46e5285d16e0afe 0 1520333367008 13 connected
e073db09e7aaed3c20d133726a26c8994932262c 192.168.11.202:6388 master - 0 1520333371031 15 connected

　　　　2、忘記節點

　　　　由於集群內的節點不停地通過Gossip消息彼此交換節點信息，因此需要通過一種健壯的機制讓集群內所有節點忘記下線的節點。也就是說讓其他節點不再與要下線的節點進行Gossip消息交換。

　　　　利用redis-trib.rb del-node命令實現節點下線，先下線從節點再下線主節點，避免不必要的全量復制。命令如下

[root@slave1 redis_cluster]# ./../src/redis-trib.rb del-node 192.168.11.202:6389 37de0d2dc1c267760156d4230502fa96a6bba64d
[root@slave1 redis_cluster]# ./../src/redis-trib.rb del-node 192.168.11.202:6388 e073db09e7aaed3c20d133726a26c8994932262c

　　　　集群節點信息如下

192.168.11.202:6382> cluster nodes
3771e67edab547deff6bd290e1a07b23646906ee 192.168.11.202:6383 master - 0 1520333828887 16 connected 5461-10922
0ec055f9daa5b4f570e6a4c4d46e5285d16e0afe 192.168.11.202:6382 myself,master - 0 0 13 connected 0-5460
10b3789bb30889b5e6f67175620feddcd496d19e 192.168.11.202:6384 master - 0 1520333827377 17 connected 10923-16383
4f36b08d8067a003af45dbe96a5363f348643509 192.168.11.202:6386 slave 3771e67edab547deff6bd290e1a07b23646906ee 0 1520333826880 16 connected
a583def1e6a059e4fdb3592557fd6ab691fd61ec 192.168.11.202:6387 slave 10b3789bb30889b5e6f67175620feddcd496d19e 0 1520333829892 17 connected
7649466ec006e0902a7f1578417247a6d5540c47 192.168.11.202:6385 slave 0ec055f9daa5b4f570e6a4c4d46e5285d16e0afe 0 1520333827879 13 connected

　　　　16384個槽節點都有分布，集群狀態ok，節點6389和6388下線成功

注意點

　　1、創建集群的時候，redis-trib.rb會盡可能保證主從節點不分配在同一機器下，因此會重新排序節點順序；節點列表順序用於確定主從角色，先主節點之后是從節點

　　2、redis-trib.rb創建集群的時候，節點地址必須是不包含任何槽 / 數據的節點，否則會拒絕創建集群

　　3、虛擬槽的采用主要是針對一致性哈希分區的不足而提出的，一致性哈希分區不適用少量節點的情況，而虛擬槽的范圍（redis cluster槽范圍是0 ~ 16383）一般遠大於節點數的，然后每個節點負責一定數量的槽，這樣就規避掉了少量節點的問題，因為在數據與節點之間多了一層虛擬槽的映射

　　4、Jedis連接redis cluster的時候，配置redis-cluster節點的時候只需要配置任意一個可達的節點即可，不一定全部節點都配置上，因為每個節點都有整個集群的信息；Jedis鍵命令執行流程如下圖，有興趣的朋友可以查看Jedis源碼；當然，全部節點都配置是更全面的做法

　　5、集群的伸縮與故障轉移對客戶端沒有影響，只要整個集群狀態是ok，那么客戶端的請求都是能夠得到正常響應的

　　6、只有保證16384個槽節點都能分配到節點上，那么集群狀態就是ok，才能正常對外提供服務；所以無論是集群擴容還是收縮，都必須保證16384個槽能正確的分配到節點上

參考

　　《Redis開發與運維》

　　Redis 集群教程

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