Redis應用Consistent Hash分佈式算法原理，連接池及接口封裝

Consistent Hash （分佈式算法）

將0到2^32-1的數軸首尾相連，key和Cache採用同樣的hash算法計算並分佈在環行數軸上，每一個key存儲在順時針方向離它最近的一個Cache中。

**hash傾斜性：**導致Cache節點分佈不均勻導致有些Server負載過大，有些Server過於空閒。
解決： 引入虛擬節點
命中率公式：（1-n/(n+m))*100% n：服務器臺數，m：新增臺數

**Redis應用：**使用SharedJedisPool，初始化時指定。

RedisSharedPool連接池

public class RedisShardedPool {
    private static ShardedJedisPool pool;//sharded jedis連接池
    private static Integer maxTotal = Integer.parseInt(PropertiesUtil.getProperty("redis.max.total","20")); //最大連接數
    private static Integer maxIdle = Integer.parseInt(PropertiesUtil.getProperty("redis.max.idle","20"));//在jedispool中最大的idle狀態(空閒的)的jedis實例的個數
    private static Integer minIdle = Integer.parseInt(PropertiesUtil.getProperty("redis.min.idle","20"));//在jedispool中最小的idle狀態(空閒的)的jedis實例的個數

    private static Boolean testOnBorrow = Boolean.parseBoolean(PropertiesUtil.getProperty("redis.test.borrow","true"));//在borrow一個jedis實例的時候，是否要進行驗證操作，如果賦值true。則得到的jedis實例肯定是可以用的。
    private static Boolean testOnReturn = Boolean.parseBoolean(PropertiesUtil.getProperty("redis.test.return","true"));//在return一個jedis實例的時候，是否要進行驗證操作，如果賦值true。則放回jedispool的jedis實例肯定是可以用的。

    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);//連接耗盡的時候，是否阻塞，false會拋出異常，true阻塞直到超時。默認爲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);

        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 returnBrokenResource(ShardedJedis jedis){
        pool.returnBrokenResource(jedis);
    }


    public static void returnResource(ShardedJedis jedis){
        pool.returnResource(jedis);
    }


    public static void main(String[] args) {
        ShardedJedis jedis = pool.getResource();

        for(int i =0;i<10;i++){
            jedis.set("key"+i,"value"+i);
        }
        returnResource(jedis);

//        pool.destroy();//臨時調用，銷燬連接池中的所有連接
        System.out.println("program is end");


    }
}

RedisSharedPoolUtil 封裝接口

@Slf4j
public class RedisShardedPoolUtil {

    /**
     * 設置key的有效期，單位是秒
     * @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.returnBrokenResource(jedis);
            return result;
        }
        RedisShardedPool.returnResource(jedis);
        return result;
    }

    //exTime的單位是秒
    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.returnBrokenResource(jedis);
            return result;
        }
        RedisShardedPool.returnResource(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.returnBrokenResource(jedis);
            return result;
        }
        RedisShardedPool.returnResource(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:{} value:{} error",key,value,e);
            RedisShardedPool.returnBrokenResource(jedis);
            return result;
        }
        RedisShardedPool.returnResource(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.returnBrokenResource(jedis);
            return result;
        }
        RedisShardedPool.returnResource(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.returnBrokenResource(jedis);
            return result;
        }
        RedisShardedPool.returnResource(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.returnBrokenResource(jedis);
            return result;
        }
        RedisShardedPool.returnResource(jedis);
        return result;
    }


    public static void main(String[] args) {
        ShardedJedis jedis = RedisShardedPool.getJedis();

        RedisPoolUtil.set("keyTest","value");

        String value = RedisPoolUtil.get("keyTest");

        RedisPoolUtil.setEx("keyex","valueex",60*10);

        RedisPoolUtil.expire("keyTest",60*20);

        RedisPoolUtil.del("keyTest");


        String aaa = RedisPoolUtil.get(null);
        System.out.println(aaa);

        System.out.println("end");


    }

}