总结之redis分布式应用和算法原理

深碍√TFBOYSˉ_ 2023-05-22 08:47 8阅读 0赞

## 一、分布式算法原理 ##

**1传统的分布式算法.**  
即对缓存项的键进行哈希，将hash后的结果对缓存服务器的数量进行取模操作，通过取模后的结果，决定缓存项将会缓存在哪一台服务器上。  
**2Consistent hashing一致性算法原理**  
命中率=（1 - n /（n+m））\*100%（注释： n = 现有的节点数量；m = 新增的节点数量）  
具体介介绍下文很清晰  
https://www.jianshu.com/p/af7d933439a3

## 二、分布式缓存环境搭建 ##

准备两个redis server 修改p配置不同端口6379、6380，一个是默认，  
另一个是redis.conf修改端口为6380  
![在这里插入图片描述][20200416214905113.png]

## 三、封装分布式Shard Redis API ##

那么，我们存储一个数据，他会存在哪个redis服务器上呢？那我们要是取该如何取呢？这是我们需要关心的事情。  
pom.xml

<dependency>
                <groupId>redis.clients</groupId>
                <artifactId>jedis</artifactId>
                <version>2.9.0</version>
            </dependency>

RedisShardedPool.java

import lombok.extern.slf4j.Slf4j;
    import redis.clients.jedis.*;
    import redis.clients.util.Hashing;
    import redis.clients.util.Sharded;
    
    import java.util.ArrayList;
    import java.util.List;
    
    /**
     * Created by maniy
     */
    @Slf4j
    public class RedisShardedPool {
        private static ShardedJedisPool pool;//sharded jedis连接池
        private static Integer maxTotal = Integer.parseInt(PropertiesUtil.getProperty("redis.max.total","20")); //最大连接数
        private static Integer maxIdle = Integer.parseInt(PropertiesUtil.getProperty("redis.max.idle","20"));//在jedispool中最大的idle状态(空闲的)的jedis实例的个数
        private static Integer minIdle = Integer.parseInt(PropertiesUtil.getProperty("redis.min.idle","20"));//在jedispool中最小的idle状态(空闲的)的jedis实例的个数
    
        private static Boolean testOnBorrow = Boolean.parseBoolean(PropertiesUtil.getProperty("redis.test.borrow","true"));//在borrow一个jedis实例的时候，是否要进行验证操作，如果赋值true。则得到的jedis实例肯定是可以用的。
        private static Boolean testOnReturn = Boolean.parseBoolean(PropertiesUtil.getProperty("redis.test.return","true"));//在return一个jedis实例的时候，是否要进行验证操作，如果赋值true。则放回jedispool的jedis实例肯定是可以用的。
    
        private static String redis1Ip = PropertiesUtil.getProperty("redis1.ip");
        private static Integer redis1Port = Integer.parseInt(PropertiesUtil.getProperty("redis1.port"));
        private static String redis2Ip = PropertiesUtil.getProperty("redis2.ip");
        private static Integer redis2Port = Integer.parseInt(PropertiesUtil.getProperty("redis2.port"));
    
    
    
    
        private static void initPool(){
            JedisPoolConfig config = new JedisPoolConfig();
    
            config.setMaxTotal(maxTotal);
            config.setMaxIdle(maxIdle);
            config.setMinIdle(minIdle);
    
            config.setTestOnBorrow(testOnBorrow);
            config.setTestOnReturn(testOnReturn);
    
            config.setBlockWhenExhausted(true);//连接耗尽的时候，是否阻塞，false会抛出异常，true阻塞直到超时。默认为true。
    
            JedisShardInfo info1 = new JedisShardInfo(redis1Ip,redis1Port,1000*2);
    
            JedisShardInfo info2 = new JedisShardInfo(redis2Ip,redis2Port,1000*2);
    
            List<JedisShardInfo> jedisShardInfoList = new ArrayList<JedisShardInfo>(2);
    
            jedisShardInfoList.add(info1);
            jedisShardInfoList.add(info2);
            //这就是我上面说的一些参数啥的hash算法之类的
            pool = new ShardedJedisPool(config,jedisShardInfoList, Hashing.MURMUR_HASH, Sharded.DEFAULT_KEY_TAG_PATTERN);
        }
    
        static{
            initPool();
        }
    
        public static ShardedJedis getJedis(){
            return pool.getResource();
        }
    
    
        public static void close(ShardedJedis jedis){
            try {
                if (jedis != null) {
                    jedis.close();
                }
            } catch (Exception e) {
                log.error("return redis resource exception", e);
            }
        }
    
    
        public static void main(String[] args) {
            /*ShardedJedis jedis = pool.getResource();
            System.out.println(jedis.get("key1"));
            for(int i =0;i<10;i++){
                jedis.set("key"+i,"value"+i);
            }
            close(jedis);
    
            pool.destroy();//临时调用，销毁连接池中的所有连接
            System.out.println("program is end");*/
            pool.destroy();//临时调用，销毁连接池中的所有连接
    
        }
    }

RedisShardedPoolUtil.java

import lombok.extern.slf4j.Slf4j;
    import redis.clients.jedis.ShardedJedis;
    
    /**
     * Created by maniy
     */
    @Slf4j
    public class RedisShardedPoolUtil {
    
        /**
         * 设置key的有效期，单位是秒
         * @param key
         * @param exTime
         * @return
         */
        public static Long expire(String key,int exTime){
            ShardedJedis jedis = null;
            Long result = null;
            try {
                jedis = RedisShardedPool.getJedis();
                result = jedis.expire(key,exTime);
            } catch (Exception e) {
                log.error("expire key:{} error",key,e);
                RedisShardedPool.close(jedis);
                return result;
            }
            RedisShardedPool.close(jedis);
            return result;
        }
    
        //exTime的单位是秒
        public static String setEx(String key,String value,int exTime){
            ShardedJedis jedis = null;
            String result = null;
            try {
                jedis = RedisShardedPool.getJedis();
                result = jedis.setex(key,exTime,value);
            } catch (Exception e) {
                log.error("setex key:{} value:{} error",key,value,e);
                RedisShardedPool.close(jedis);
                return result;
            }
            RedisShardedPool.close(jedis);
            return result;
        }
    
        public static String set(String key,String value){
            ShardedJedis jedis = null;
            String result = null;
    
            try {
                jedis = RedisShardedPool.getJedis();
                result = jedis.set(key,value);
            } catch (Exception e) {
                log.error("set key:{} value:{} error",key,value,e);
                RedisShardedPool.close(jedis);
                return result;
            }
            RedisShardedPool.close(jedis);
            return result;
        }
    
        public static String get(String key){
            ShardedJedis jedis = null;
            String result = null;
            try {
                jedis = RedisShardedPool.getJedis();
                result = jedis.get(key);
            } catch (Exception e) {
                log.error("get key:{} error",key,e);
                RedisShardedPool.close(jedis);
                return result;
            }
            RedisShardedPool.close(jedis);
            return result;
        }
    
        public static Long del(String key){
            ShardedJedis jedis = null;
            Long result = null;
            try {
                jedis = RedisShardedPool.getJedis();
                result = jedis.del(key);
            } catch (Exception e) {
                log.error("del key:{} error",key,e);
                RedisShardedPool.close(jedis);
                return result;
            }
            RedisShardedPool.close(jedis);
            return result;
        }
    
    
        public static String getSet(String key,String value) {
            ShardedJedis jedis = null;
            String result = null;
            try {
                jedis = RedisShardedPool.getJedis();
                result = jedis.getSet(key,value);
            } catch (Exception e) {
                log.error("getset key:{} error", key, e);
                RedisShardedPool.close(jedis);
                return result;
            }
            RedisShardedPool.close(jedis);
            return result;
        }
    
        public static Long setnx(String key, String value) {
            ShardedJedis jedis = null;
            Long result = null;
            try {
                jedis = RedisShardedPool.getJedis();
                result = jedis.setnx(key, value);
            } catch (Exception e) {
                log.error("setnx key:{} value:{} error", key, value, e);
                RedisShardedPool.close(jedis);
                return result;
            }
            RedisShardedPool.close(jedis);
            return result;
        }
    
    
        public static void main(String[] args) {
            ShardedJedis jedis = RedisShardedPool.getJedis();
    
            System.out.println(jedis.get("key1"));
    
            System.out.println("end");
    
    
        }
    
    
    
    }

application.properties

#redis config start
    
    redis1.ip=127.0.0.1
    redis1.port=6379
    
    redis2.ip=127.0.0.1
    redis2.port=6380
    ##Tips：以上redis1和redis2的ip和port改成你自己的哟
    
    #最大连接数
    redis.max.total=20
    
    #最大空闲数
    redis.max.idle=10
    
    #最小空闲数
    redis.min.idle=2
    
    #从jedis连接池获取连接时，校验并返回可用的连接
    redis.test.borrow=true
    
    #把连接放回jedis连接池时，校验并返回可用的连接
    redis.test.return=false
    
    
    #redis config end

PropertiesUtil.java

import lombok.extern.slf4j.Slf4j;
    import org.apache.commons.lang3.StringUtils;
    
    import java.io.IOException;
    import java.io.InputStreamReader;
    import java.util.Properties;
    
    /**
     * Created by maniy
     */
    @Slf4j
    public class PropertiesUtil {
    
    
        private static Properties props;
    
        static {
            String fileName = "mmall.properties";
            props = new Properties();
            try {
                props.load(new InputStreamReader(PropertiesUtil.class.getClassLoader().getResourceAsStream(fileName),"UTF-8"));
            } catch (IOException e) {
                log.error("配置文件读取异常",e);
            }
        }
    
        public static String getProperty(String key){
            String value = props.getProperty(key.trim());
            if(StringUtils.isBlank(value)){
                return null;
            }
            return value.trim();
        }
    
        public static String getProperty(String key,String defaultValue){
    
            String value = props.getProperty(key.trim());
            if(StringUtils.isBlank(value)){
                value = defaultValue;
            }
            return value.trim();
        }
    
        public static void main(String[] arg){
            System.out.println(PropertiesUtil.getProperty("redis.port"));
        }
    
    }

我们去添加key时，在两个redis里面就是分布存在了。  
末: redis知识点集  
https://zhuanlan.zhihu.com/p/112944545

[20200416214905113.png]: /images/20230521/6db631c7e8d34c509199c0dfe6a3e978.png