Redis——SpringBoot项目使用Lettuce和Jedis接入Redis集群

Jedis连接Redis：

非线程安全

如果是多线程环境下共用一个Jedis连接池，会产生线程安全问题，可以通过创建多个Jedis实例来解决，但是创建许多socket会影响性能，因此好一点的方法是使用JedisPool

https://blog.csdn.net/lihao21/article/details/46830553

https://www.jianshu.com/p/5e4a1f92c88f

为什么 jedis不是线程安全的，可以通过一个demo来说明：

public class BadConcurrentJedisTest {

    private static final ExecutorService pool = Executors.newFixedThreadPool(20);

    private static final Jedis jedis = new Jedis("127.0.0.1", 6379);

    public static void main(String[] args) {
        for(int i=0;i<20;i++){
            pool.execute(new RedisSet());
        }
    }

    static class RedisSet implements Runnable{

        @Override
        public void run() {
            while(true){
                jedis.set("hello", "world");
            }
        }

    }

这时候后台报错：

redis.clients.jedis.exceptions.JedisConnectionException: java.net.SocketException: Socket Closed

主要的原因就在于jedis实例中的两个成员变量：RedisInputStream和RedisOutputStream

jedis在执行每一个命令之前都会先执行connect方法，socket是一个共享变量，在多线程的情况下可能存在：线程1执行到：

outputStream = new RedisOutputStream(socket.getOutputStream());
inputStream = new RedisInputStream(socket.getInputStream());

线程2执行到：

socket = new Socket();
socket.connect(new InetSocketAddress(host, port), connectionTimeout);

因为线程2重新初始化了socket但是还没有执行connect，所以线程1执行socket.getOutputStream()或者socket.getInputStream()就会抛出java.net.SocketException: Socket is not connected。

Jedis解决线程安全的方式就是使用连接池：

每个线程去连接池中获取一个Jedis实例，这样就在有限个socket的情况下保证了线程安全

Lettuce连接Redis：

线程安全

Lettuce是基于netty的，性能比较好。

多线程使用同一连接实例时，是线程安全的。

application-test.yml

redis:
  nodes:
    - host1:port1
    - host2:port2

-----------------------------------------------------------------Lettuce-----------------------------------------------------------------

导入依赖：

    //Redis
    compile 'org.springframework.boot:spring-boot-starter-data-redis-reactive'

配置类：

import io.lettuce.core.RedisURI;
import io.lettuce.core.cluster.RedisClusterClient;
import io.lettuce.core.cluster.api.StatefulRedisClusterConnection;
import io.lettuce.core.cluster.api.sync.RedisClusterCommands;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import java.util.ArrayList;
import java.util.List;

@Configuration
@ConfigurationProperties(prefix = "redis")
public class LettuceConfig {
    private List<String> nodes;

    public List<String> getNodes() {
        return nodes;
    }

    public void setNodes(List<String> nodes) {
        this.nodes = nodes;
    }

    @Bean
    RedisClusterCommands<String, String> redisCommands() {
        List<RedisURI> uriList = new ArrayList<>();
        nodes.forEach(node -> {
            String[] addrStr = node.split(":");
            String host = addrStr[0];
            int port = Integer.parseInt(addrStr[1]);

            RedisURI redisUri = RedisURI.Builder.redis(host).withPort(port).build();
            uriList.add(redisUri);
        });
        RedisClusterClient redisClient = RedisClusterClient.create(uriList);
        StatefulRedisClusterConnection<String, String> connection = redisClient.connect();
        RedisClusterCommands<String, String> syncCommands = connection.sync();

        return syncCommands;
    }

}

-----------------------------------------------------------------Jedis-----------------------------------------------------------------

导入依赖：

compile group: 'redis.clients', name: 'jedis', version: '2.9.0'

配置类：

package com.youdao.outfox.interflow.config;

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Profile;
import redis.clients.jedis.HostAndPort;
import redis.clients.jedis.JedisCluster;

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

@Configuration
@ConfigurationProperties(prefix = "redis")
public class JedisClusterConfig {

    private List<String> nodes;

    public List<String> getNodes() {
        return nodes;
    }

    public void setNodes(List<String> nodes) {
        this.nodes = nodes;
    }

    @Bean
    public JedisCluster jedisCluster() {
        Set<HostAndPort> jedisClusterNodes = new HashSet<>();
        nodes.forEach(node -> {
            String[] addrStr = node.split(":");
            String host = addrStr[0];
            int port = Integer.parseInt(addrStr[1]);
            jedisClusterNodes.add(new HostAndPort(host, port));
        });
        return new JedisCluster(jedisClusterNodes, 5, 2);
    }
}

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