分布式鎖的使用-有解無憂

一、分布式鎖介紹

由于傳統的鎖是基于Tomcat服務器的內部物件,搭建了集群之后,導致鎖失效,所以要使用分布式鎖來處理↓

分布式鎖介紹

二、分布式鎖解決方案

3.1 搭建環境

創建SpringBoot工程,起名為秒殺second-kill,勾選web依賴↓

搶購的業務邏輯代碼↓

package com.ljh.controller;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.HashMap;
import java.util.Map;

@RestController
public class SecondKillController {
    //1. 準備商品的庫存
    public static Map<String,Integer> itemStock = new HashMap<>();
    //2. 準備商品的訂單
    public static Map<String,Integer> itemOrder = new HashMap<>();

    static{
        itemStock.put("牙刷",10000);
        itemOrder.put("牙刷",0);
    }

    @GetMapping("/kill")//item表示用戶訪問的商品名稱,等會瀏覽器地址欄我會輸入牙刷
    public String kill(String item) throws InterruptedException {
        //1. 減庫存
        Integer stock = itemStock.get(item);
        
        if(stock <= 0){
            return "商品庫存數不足！！！";
        }
        
        Thread.sleep(100);//用睡眠來模擬消耗時間
        itemStock.put(item,stock-1);

        //2. 創建訂單
        Thread.sleep(100);
        itemOrder.put(item,itemOrder.get(item)+1);

        //3. 回傳資訊
        return "搶購成功！！！" + item + "： 剩余庫存數為" + itemStock.get(item) + "，訂單數為" + itemOrder.get(item);
    }
}

用瀏覽器訪問我們的控制器方法,庫存和訂單確實加起來是10000,沒有超賣,但是我們別忘了還有其他用戶的訪問↓

http://localhost:8080/kill?item=牙刷

在這里插入圖片描述

下載ab壓力測驗工具軟體,解壓軟體即可,找到bin目錄,cmd打開,輸入下面地址來模擬1000個請求和500并發↓

下載鏈接：https://pan.baidu.com/s/1yHeVgXN94kram3Jxj5V13w
提取碼：6qfh
ab -n 請求數 -c 并發數 訪問的路徑(復制瀏覽器地址過來,瀏覽器地址欄對牙刷進行了url編碼所以是這樣的↓)
ab -n 1000 -c 500 http://localhost:8080/kill?item=%E7%89%99%E5%88%B7

enter回車,看到執行完了請求和并發,然后打開瀏覽器地址值,再訪問發現庫存和訂單加起來不是10000,超賣了↓

3.2 Zookeeper實作分布式鎖原理圖解

Zookeeper實作分布式鎖原理圖解

這里用臨時節點有個好處,斷開連接,鎖資源就會消失,不用設定過期時間,而下面用redis做分布式鎖需要過期時間

3.3 Zookeeper實作分布式鎖代碼實作

在上面寫的秒殺工程里面匯入依賴來解決問題

<dependency>
    <groupId>org.apache.zookeeper</groupId>
    <artifactId>zookeeper</artifactId>
    <version>3.6.0</version>
    <exclusions>
        <exclusion>
            <artifactId>slf4j-api</artifactId>
            <groupId>org.slf4j</groupId>
        </exclusion>
        <exclusion>
            <artifactId>slf4j-log4j12</artifactId>
            <groupId>org.slf4j</groupId>
        </exclusion>
        <exclusion>
            <artifactId>log4j</artifactId>
            <groupId>log4j</groupId>
        </exclusion>
    </exclusions>
</dependency>

<dependency>
    <groupId>org.apache.curator</groupId>
    <artifactId>curator-recipes</artifactId>
    <version>2.7.1</version>
</dependency>

配置類

package com.ljh.config;

import org.apache.curator.RetryPolicy;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.retry.ExponentialBackoffRetry;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class ZkConfig {
    @Bean
    public CuratorFramework cf(){
        RetryPolicy retryPolicy = new ExponentialBackoffRetry(3000,2);//需要指定重試間隔和重試次數

        CuratorFramework curatorFramework = CuratorFrameworkFactory.builder()
                .connectString("10.20.159.39:2181,10.20.159.39:2182,10.20.159.39:2183")
                .retryPolicy(retryPolicy)
                .build();

        curatorFramework.start();

        return curatorFramework;
    }
}

在業務代碼中添加分布式鎖

InterProcessMutex lock = new InterProcessMutex(cf,"/lock");

//加鎖
lock.acquire();
lock.acquire(1,TimeUnit.SECONDS); //指定排隊多久放棄獲取鎖資源

//----------------業務邏輯代碼------------------------

//釋放鎖
lock.release();

package com.ljh.controller;

import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.recipes.locks.InterProcessMutex;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.TimeUnit;

@RestController
public class SecondKillController {
    //1. 準備商品的庫存
    public static Map<String,Integer> itemStock = new HashMap<>();
    //2. 準備商品的訂單
    public static Map<String,Integer> itemOrder = new HashMap<>();

    static{
        itemStock.put("牙刷",10000);
        itemOrder.put("牙刷",0);
    }

    @Autowired
    private CuratorFramework cf;

    @GetMapping("/kill")//item表示用戶訪問的商品名稱,等會瀏覽器地址欄我會輸入牙刷
    public String kill(String item) throws Exception {
        InterProcessMutex lock = new InterProcessMutex(cf,"/lock");

        //加鎖
        lock.acquire();
        //lock.acquire(1,TimeUnit.SECONDS); //指定排隊多久放棄獲取鎖資源

        //----------------業務邏輯代碼↓------------------------
        //1. 減庫存
        Integer stock = itemStock.get(item);

        if(stock <= 0){
            return "商品庫存數不足！！！";
        }

        Thread.sleep(100);//用睡眠來模擬消耗時間
        itemStock.put(item,stock-1);

        //2. 創建訂單
        Thread.sleep(100);
        itemOrder.put(item,itemOrder.get(item)+1);
        //----------------業務邏輯代碼↑------------------------

        //釋放鎖
        lock.release();

        //3. 回傳資訊
        return "搶購成功！！！" + item + "： 剩余庫存數為" + itemStock.get(item) + "，訂單數為" + itemOrder.get(item);
    }
}

package com.ljh.controller;

import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.recipes.locks.InterProcessMutex;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.TimeUnit;

@RestController
public class SecondKillController2 {
    //1. 準備商品的庫存
    public static Map<String,Integer> itemStock = new HashMap<>();
    //2. 準備商品的訂單
    public static Map<String,Integer> itemOrder = new HashMap<>();

    static{
        itemStock.put("牙刷",10000);
        itemOrder.put("牙刷",0);
    }

    @Autowired
    private CuratorFramework cf;

    @RequestMapping(value = "/seckill")
    public String seckill(String gname) throws Exception {
        InterProcessMutex interProcessMutex = new InterProcessMutex(cf, "/seckill_lock");

        //獲取鎖
        //interProcessMutex.acquire();//沒有獲取到鎖就一直等待
        if(interProcessMutex.acquire(1, TimeUnit.SECONDS)){//等待1s就放棄獲取鎖資源
            //1.先減庫存
            Integer stock = itemStock.get(gname);
            if (stock <= 0) {
                return "庫存不足，，，，";
            }
            itemStock.put(gname, stock - 1);
            Thread.sleep(100);

            //2.加訂單數量
            Integer count = itemOrder.get(gname);
            itemOrder.put(gname, count + 1);
            Thread.sleep(100);

            //釋放鎖
            interProcessMutex.release();

            return "搶購成功【" + gname + "】,庫存:" + itemStock.get(gname) + ",訂單:" + itemOrder.get(gname);
        }else{
            return "請稍后再試";
        }
    }
}

修改完代碼重啟秒殺工程,發現不管用瀏覽器訪問,還是用之前的ab壓測工具軟體訪問,庫存和訂單加起來都是10000

注意,如果啟動報下面這個錯,要重啟防火墻,然后關閉防火墻↓

在這里插入圖片描述

systemctl start firewalld
systemctl stop firewalld

3.4 Redis實作分布式鎖原理圖解

Redis實作分布式鎖原理

這里出現了例外不走后面釋放鎖資源的代碼怎么辦?簡單,為鎖資源設定過期時間來防止死鎖的發生

3.5 Redis實作分布式鎖代碼實作

上面的秒殺工程匯入redis依賴,添加組態檔

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>

# yml組態檔,配置redis服務器的ip和埠↓
spring:
  redis:
    host: xx.xx.xx.xx #redis服務器的ip地址
    port: xxxx #redis埠

工具類

package com.ljh.utils;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.util.concurrent.TimeUnit;

@Component
public class RedisLockUtil {
    @Autowired
    private StringRedisTemplate redisTemplate;

    public boolean lock(String key,String value,int second){
        return redisTemplate.opsForValue().setIfAbsent(key,value,second, TimeUnit.SECONDS);
    }

    public void unlock(String key){
        redisTemplate.delete(key);
    }
}

修改業務邏輯代碼

@Autowired
private RedisLockUtil lock;

@GetMapping("/redis/kill")
public String redisKill(String item) throws Exception {
    //加鎖
    if(lock.lock(item,System.currentTimeMillis() + "",1)){
        //業務代碼...
        //釋放鎖
        lock.unlock(item);
    }
}

package com.ljh.controller;

import com.ljh.utils.RedisLockUtil;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.recipes.locks.InterProcessMutex;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.TimeUnit;

@RestController
public class SecondKillController {
    //1. 準備商品的庫存
    public static Map<String,Integer> itemStock = new HashMap<>();
    //2. 準備商品的訂單
    public static Map<String,Integer> itemOrder = new HashMap<>();

    static{
        itemStock.put("牙刷",10000);
        itemOrder.put("牙刷",0);
    }

    @Autowired
    private RedisLockUtil lock;

    @GetMapping("/kill")//item表示用戶訪問的商品名稱,等會瀏覽器地址欄我會輸入牙刷
    public String kill(String item) throws Exception {
        //加鎖
        if(lock.lock(item,System.currentTimeMillis() + "",1)){
            //業務代碼
            //----------------業務邏輯代碼↓------------------------
            //1. 減庫存
            Integer stock = itemStock.get(item);

            if(stock <= 0){
                return "商品庫存數不足！！！";
            }

            Thread.sleep(100);//用睡眠來模擬消耗時間
            itemStock.put(item,stock-1);

            //2. 創建訂單
            Thread.sleep(100);
            itemOrder.put(item,itemOrder.get(item)+1);
            //----------------業務邏輯代碼↑------------------------

            //釋放鎖
            lock.unlock(item);
        }

        //3. 回傳資訊
        return "搶購成功！！！" + item + "： 剩余庫存數為" + itemStock.get(item) + "，訂單數為" + itemOrder.get(item);
    }
}

修改完代碼重啟秒殺工程,發現不管用瀏覽器訪問,還是用之前的ab壓測工具軟體訪問,庫存和訂單加起來都是10000

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