『互联网架构』软件架构-redis的通信协议（protocol）（52）

redis的通信协议是什么？双方约定了一种编码方式，客户端将要发送的命令进行编码，然后服务端收到后，使用同样的协议进行解码，服务端处理完成后，再次编码返回给客户端，客户端解码拿到返回结果，这样就完成了一次通信。

（一）协议介绍

 https://redis.io/topics/protocol 

1. 易于实现
2. 可以高效地被计算机分析（parse）
3. 可以很容易地被人类读懂

（二）编码后的字符标记解释

1. For Simple Strings the first byte of the reply is “+” 回复
2. For Errors the first byte of the reply is “-” 错误
3. For Integers the first byte of the reply is “:” 整数
4. For Bulk Strings the first byte of the reply is “$” 字符串
5. For Arrays the first byte of the reply is “*” 数组

（三）模拟Redis客户端&分片

• 客户端

  > Jedis跟redis通讯很简单发送了socket，然后发送了resp这种‘暗语’进行通讯。

import java.io.IOException;
import java.io.InputStream;
import java.net.Socket;

public class RedisClient {

    private Socket socket;
    private  String host;
    private int port;

    public RedisClient() throws IOException {
        this.socket = new Socket("192.168.79.100",6379);
    }

    public RedisClient(String host, int port) {
        this.host = host;
        this.port = port;
        try {
            this.socket = new Socket(host,port);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    //set wk 2018
    public String set( String key, String value) throws IOException {
       //"*3/r/n$3/r/nset/r/n$2/r/nwk/r/n$4/r/n2018"
        StringBuilder stringBuilder=new StringBuilder();
        stringBuilder.append("*3").append("/r/n");
        stringBuilder.append("$").append(CommandRedis.set.name().length()).append("/r/n");
        stringBuilder.append(CommandRedis.set).append("/r/n");
        stringBuilder.append("$").append(key.getBytes().length).append("/r/n");
        stringBuilder.append(key).append("/r/n");
        stringBuilder.append("$").append(value.getBytes().length).append("/r/n");
        stringBuilder.append(value).append("/r/n");
        socket.getOutputStream().write(stringBuilder.toString().getBytes());
        byte[] b=new byte[2048];
        socket.getInputStream().read(b);
        return new String(b);

    }


    public String get( String key) throws IOException {
        //"*3/r/n$3/r/nset/r/n$2/r/nwk/r/n$4/r/n2018"
        StringBuilder stringBuilder=new StringBuilder();
        stringBuilder.append("*2").append("/r/n");
        stringBuilder.append("$").append(CommandRedis.get.name().length()).append("/r/n");
        stringBuilder.append(CommandRedis.get).append("/r/n");
        stringBuilder.append("$").append(key.getBytes().length).append("/r/n");
        stringBuilder.append(key).append("/r/n");
        socket.getOutputStream().write(stringBuilder.toString().getBytes());
        byte[] b=new byte[2048];
        socket.getInputStream().read(b);
        return new String(b);

    }

    public String setnx(String key, String value) throws Exception {
        StringBuffer stringBuffer = new StringBuffer();
        stringBuffer.append("*3").append("/r/n");
        stringBuffer.append("$5").append("/r/n");
        stringBuffer.append("setnx").append("/r/n");
        stringBuffer.append("$").append(key.getBytes().length).append("/r/n");
        stringBuffer.append(key).append("/r/n");
        stringBuffer.append("$").append(value.getBytes().length).append("/r/n");
        stringBuffer.append(value).append("/r/n");
        socket.getOutputStream().write(stringBuffer.toString().getBytes());
        byte[] b = new byte[2048];
        socket.getInputStream().read(b );
        return new String(b);
    }

    // 管道
    public void pipeline(String key)throws Exception {
        StringBuffer stringBuffer = new StringBuffer();
        stringBuffer.append("*2").append("/r/n");
        stringBuffer.append("$"+CommandRedis.subscribe.name().length()).append("/r/n");
        stringBuffer.append(CommandRedis.subscribe).append("/r/n");
        stringBuffer.append("$").append(key.getBytes().length).append("/r/n");
        stringBuffer.append(key).append("/r/n");
        socket.getOutputStream().write(stringBuffer.toString().getBytes());
        InputStream inputStream = socket.getInputStream();
        while (true) {
            byte[] b = new byte[2048];
            inputStream.read(b );
            System.out.println(new String(b));
        }

    }

    //subscribe
    public void subscribe(String key)throws Exception {
        StringBuffer stringBuffer = new StringBuffer();
        stringBuffer.append("*2").append("/r/n");
        stringBuffer.append("$"+CommandRedis.subscribe.name().length()).append("/r/n");
        stringBuffer.append(CommandRedis.subscribe).append("/r/n");
        stringBuffer.append("$").append(key.getBytes().length).append("/r/n");
        stringBuffer.append(key).append("/r/n");
        socket.getOutputStream().write(stringBuffer.toString().getBytes());
        InputStream inputStream = socket.getInputStream();
        while (true) {
            byte[] b = new byte[2048];
            inputStream.read(b );
            System.out.println(new String(b));
        }
    }

    public void close(){
        if(socket != null){
            try {
                socket.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

}

public enum CommandRedis {

    set,get,incr,subscribe

}

• 分片

  > RedisClient分片方式，简单模拟，理解概念分片。

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class TestRedisClient {
    public static void main(String[] args) throws IOException {

 /*       RedisClient redisClient=new RedisClient();
        System.out.println(redisClient.set("wk","悟空"));
        System.out.println(redisClient.get("wk"));*/


        List<RedisClient> pool=new ArrayList<>();
        pool.add(new RedisClient("192.168.0.12",6379));
        pool.add(new RedisClient("192.168.0.12",6380));
        pool.add(new RedisClient("192.168.0.12",6381));
        Crc16Sharding crc16Sharding=new Crc16Sharding(pool);
        for (int i=0;i<100;i++){
            String key="xx"+i;

            RedisClient redisClient=crc16Sharding.crc16(key);
            redisClient.set(key,i+"");
            System.out.println(redisClient.get(key));
        }

    }
}

import com.sun.org.apache.xerces.internal.impl.xpath.regex.Match;
import java.util.List;

public class Crc16Sharding {
    List<RedisClient> pool;

    public Crc16Sharding(List<RedisClient> pool) {
        this.pool = pool;
    }

    /**
     * 通过一个key可以定位到一块 节点
     * @param key
     * @return
     */
    public RedisClient crc16(String key){

        int num=Math.abs(key.hashCode()%pool.size());
        return  pool.get(num);
       /* if(key.length()<3){
           return pool.get(0);
        }else  if(key.length()<6){
            return  pool.get(1);
        }else{
            return  pool.get(2);
        }*/
    }
}

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class TestRedisClient {
    public static void main(String[] args) throws IOException {
        List<RedisClient> pool=new ArrayList<>();
        pool.add(new RedisClient("192.168.0.12",6379));
        pool.add(new RedisClient("192.168.0.12",6380));
        pool.add(new RedisClient("192.168.0.12",6381));
        Crc16Sharding crc16Sharding=new Crc16Sharding(pool);
        for (int i=0;i<100;i++){
            String key="xx"+i;

            RedisClient redisClient=crc16Sharding.crc16(key);
            redisClient.set(key,i+"");
            System.out.println(redisClient.get(key));;
        }
    }
}

（四）redis使用技巧

1. 如果是订单表，取的话也是通过唯一的订单号来进行，不要通过循环去redis里面取。
2. 开关类型的放到本地的jvm内存中，尽量减少redis的压力。
3. 避免使用慢查询 hgetall
4. 存储redis的购物车，有的人都是很多的好几M的，几百个商品，redis存储的内容的压缩。减少通信的宽带。优化存储内容。
5. 少用字符串存储，可以存储map格式放入redis。获取redis里面的map，直接通过key就可以取到对应的值。

（五）监控&运维

• Open-falcon

  > http://open-falcon.org/

  >open-falcon是小米开源监控系统，强大灵活的数据采集、采集、传输、绘制、查询、报警等。采用全部golang编写，portal和dashboard使用python编写。

• Redis-migrate-tool

  >https://github.com/vipshop/redis-migrate-tool

  >2年多没更新了，可以了解下

  >Redis-migrate-tool是唯品会开源针对redis数据运维工具。

  支持单独、twemproxy集群、redis custer、aof、rdb文件迁移。支持实时迁移、异构迁移、过滤等功能。

PS：介绍了运维工具，redis通信的内容拼接，redis存储的技巧，redis正常的时候没问题，并发量大的时候一定要注意，在大流量的情况下，代码的细节至关重要！

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