SpringBoot系列之基于Jedis实现分布式锁
Redis系列之基于Jedis实现分布式锁
1、为什么需要分布式锁
在单机环境，我们使用最多的是juc包里的单机锁，但是随着微服务分布式项目的普及，juc里的锁是不能控制分布锁环境的线程安全的，因为单机锁只能控制同个进程里的线程安全，不能控制多节点的线程安全，所以就需要使用分布式锁
2、redis分布式锁原理
学习之前先了解redis的命令，setnx和expire
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setnx命令
SETNX是SET if not exists的简写，设置key的值，如果key值不存在，则可以设置，否则不可以设置，这个有点像juc中cas锁的原理
# setnx命令，相当于set和nx命令一起用 setnx tkey aaaEX ： 设置指定的到期时间(以秒为单位)。
PX : 设置指定的到期时间(以毫秒为单
NX ： 仅在键不存在时设置键。
XX ： 只有在键已存在时才设置。
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expire命令
如果只使用setnx不加上过期时间，手动释放锁时候出现异常，就会导致一直解不了锁，所以还是要加上expire命令来设置过期时间。
- 保证原子性
但是又有一个问题，设置过期时间时候报错了，也同样会导致锁释放不了，所以为了保证原子性，需要这两个命令一起执行
# set tkey过期时间10秒，nx：如果键不存在时设置
set tkey aaa ex 10 nx
3、基于jedis手写分布锁锁
基于上面的原理，我们就可以简单写一个分布锁锁
项目环境：
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JDK 1.8
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SpringBoot 2.2.1
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Maven 3.2+
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Mysql 8.0.26
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spring-boot-starter-data-redis 2.2.1
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jedis3.1.0
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开发工具
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IntelliJ IDEA
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smartGit
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先搭建一个springboot集成jedis的例子工程，参考我之前的博客，大体的类图如图所示：
写一个分布锁的通用接口，因为以后可能会通过其它中间件实现分布锁锁
package com.example.jedis.common;public interface DistributedLock {default boolean acquire(String lockKey, String requestId) {return acquire(lockKey, requestId, RedisConstant.DEFAULT_EXPIRE);}default boolean acquire(String lockKey, String requestId, int expireTime) {return acquire(lockKey, requestId, expireTime, RedisConstant.DEFAULT_TIMEOUT);}boolean acquire(String lockKey, String requestId, int expireTime, int timeout);boolean release(String lockKey, String requestId);}写一个抽象的分布锁锁类，实现一些可以共用的逻辑，其它的业务给子类去实现
package com.example.jedis.common;import lombok.extern.slf4j.Slf4j;import java.net.SocketTimeoutException;
import java.util.concurrent.TimeUnit;import static com.example.jedis.common.RedisConstant.DEFAULT_EXPIRE;
import static com.example.jedis.common.RedisConstant.DEFAULT_TIMEOUT;@Slf4j
public abstract class AbstractDistributedLock implements DistributedLock {@Overridepublic boolean acquire(String lockKey, String requestId, int expireTime, int timeout) {expireTime = expireTime <= 0 ? DEFAULT_EXPIRE : expireTime;timeout = timeout < 0 ? DEFAULT_TIMEOUT : timeout * 1000;long start = System.currentTimeMillis();try {do {if (doAcquire(lockKey, requestId, expireTime)) {watchDog(lockKey, requestId, expireTime);return true;}TimeUnit.MILLISECONDS.sleep(100);} while (System.currentTimeMillis() - start < timeout);} catch (Exception e) {Throwable cause = e.getCause();if (cause instanceof SocketTimeoutException) {// ignore exceptionlog.error("sockTimeout exception:{}", e);}else if (cause instanceof InterruptedException) {// ignore exceptionlog.error("Interrupted exception:{}", e);}else {log.error("lock acquire exception:{}", e);}throw new LockException(e.getMessage(), e);}return false;}@Overridepublic boolean release(String lockKey, String requestId) {try {return doRelease(lockKey, requestId);} catch (Exception e) {log.error("lock release exception:{}", e);throw new LockException(e.getMessage(), e);}}protected abstract boolean doAcquire(String lockKey, String requestId, int expireTime);protected abstract boolean doRelease(String lockKey, String requestId);protected abstract void watchDog(String lockKey, String requestId, int expireTime);}redis的分布锁锁抽象类
package com.example.jedis.common;public abstract class AbstractRedisLock extends AbstractDistributedLock{}基于jedis的分布锁实现类，主要通过lua脚本控制解锁的原子性，同时加上watch dog定时续期，避免有些长业务执行时间比较长，而锁已经释放的情况
package com.example.jedis.common;import cn.hutool.core.collection.CollUtil;
import cn.hutool.core.convert.Convert;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;import java.util.List;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;@Component
@Slf4j
public class JedisLockTemplate extends AbstractRedisLock implements InitializingBean {private String UNLOCK_LUA = "if redis.call('get', KEYS[1]) == ARGV[1] then return redis.call('del', KEYS[1]) else return 0 end";private String WATCH_DOG_LUA = "local lock_key=KEYS[1]\n" +"local lock_value=ARGV[1]\n" +"local lock_ttl=ARGV[2]\n" +"local current_value=redis.call('get',lock_key)\n" +"local result=0\n" +"if lock_value==current_value then\n" +" redis.call('expire',lock_key,lock_ttl)\n" +" result=1\n" +"end\n" +"return result";private static final Long UNLOCK_SUCCESS = 1L;private static final Long RENEWAL_SUCCESS = 1L;@Autowiredprivate JedisTemplate jedisTemplate;private ScheduledThreadPoolExecutor scheduledExecutorService;@Overridepublic void afterPropertiesSet() throws Exception {this.UNLOCK_LUA = jedisTemplate.scriptLoad(UNLOCK_LUA);this.WATCH_DOG_LUA = jedisTemplate.scriptLoad(WATCH_DOG_LUA);scheduledExecutorService = new ScheduledThreadPoolExecutor(1);}@Overridepublic boolean doAcquire(String lockKey, String requestId, int expire) {return jedisTemplate.setnxex(lockKey, requestId, expire);}@Overridepublic boolean doRelease(String lockKey, String requestId) {Object eval = jedisTemplate.evalsha(UNLOCK_LUA, CollUtil.newArrayList(lockKey), CollUtil.newArrayList(requestId));if (UNLOCK_SUCCESS.equals(eval)) {scheduledExecutorService.shutdown();return true;}return false;}@Overridepublic void watchDog(String lockKey, String requestId, int expire) {int period = getPeriod(expire);if (scheduledExecutorService.isShutdown()) {scheduledExecutorService = new ScheduledThreadPoolExecutor(1);}scheduledExecutorService.scheduleAtFixedRate(new WatchDogTask(scheduledExecutorService, CollUtil.newArrayList(lockKey), CollUtil.newArrayList(requestId, Convert.toStr(expire))),1,period,TimeUnit.SECONDS);}class WatchDogTask implements Runnable {private ScheduledThreadPoolExecutor scheduledThreadPoolExecutor;private List<String> keys;private List<String> args;public WatchDogTask(ScheduledThreadPoolExecutor scheduledThreadPoolExecutor, List<String> keys, List<String> args) {this.scheduledThreadPoolExecutor = scheduledThreadPoolExecutor;this.keys = keys;this.args = args;}@Overridepublic void run() {log.info("watch dog for renewal...");Object evalsha = jedisTemplate.evalsha(WATCH_DOG_LUA, keys, args);if (!evalsha.equals(RENEWAL_SUCCESS)) {scheduledThreadPoolExecutor.shutdown();}log.info("renewal result:{}, keys:{}, args:{}", evalsha, keys, args);}}private int getPeriod(int expire) {if (expire < 1)throw new LockException("expire不允许小于1");return expire - 1;}}写一个通用的jedis常有api的封装类，setnxex加上synchronized，因为redis是单线程的，加上同步锁，避免并发请求时候出现，jedispool加载不到的情况
package com.example.jedis.common;import cn.hutool.core.collection.ConcurrentHashSet;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.ScanParams;
import redis.clients.jedis.ScanResult;
import redis.clients.jedis.exceptions.JedisConnectionException;
import redis.clients.jedis.exceptions.JedisDataException;
import redis.clients.jedis.exceptions.JedisException;
import redis.clients.jedis.params.SetParams;import javax.annotation.Resource;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.function.Consumer;
import java.util.function.Function;@Slf4j
@Component
public class JedisTemplate implements InitializingBean {@Resourceprivate JedisPool jedisPool;private Jedis jedis;public JedisTemplate() {}@Overridepublic void afterPropertiesSet() {jedis = jedisPool.getResource();}public <T> T execute(Function<Jedis, T> action) {T apply = null;try {jedis = jedisPool.getResource();apply = action.apply(jedis);} catch (JedisException e) {handleException(e);throw e;} finally {jedis.close();}return apply;}public void execute(Consumer<Jedis> action) {try {jedis = jedisPool.getResource();action.accept(jedis);} catch (JedisException e) {handleException(e);throw e;} finally {jedis.close();}}public JedisPool getJedisPool() {return this.jedisPool;}public synchronized Boolean setnxex(final String key, final String value, int seconds) {return execute(e -> {SetParams setParams = new SetParams();setParams.nx();setParams.ex(seconds);return isStatusOk(jedis.set(key, value, setParams));});}public Object eval(final String script,final Integer keyCount,final String... params) {return execute(e -> {return jedis.eval(script, keyCount, params);});}public Object eval(final String script, final List<String> keys, final List<String> params) {return execute(e -> {return jedis.eval(script, keys, params);});}public Object evalsha(final String script, final List<String> keys, final List<String> params) {return execute(e -> {return jedis.evalsha(script, keys, params);});}public String scriptLoad(final String script) {return execute(e -> {return jedis.scriptLoad(script);});}protected void handleException(JedisException e) {if (e instanceof JedisConnectionException) {log.error("redis connection exception:{}", e);} else if (e instanceof JedisDataException) {log.error("jedis data exception:{}", e);} else {log.error("jedis exception:{}", e);}}protected synchronized static boolean isStatusOk(String status) {return status != null && ("OK".equals(status) || "+OK".equals(status));}}常量类
package com.example.jedis.common;public class RedisConstant {public static final Integer DEFAULT_EXPIRE = 30;public static final Integer DEFAULT_TIMEOUT = 1;}自定义的异常类：
package com.example.jedis.common;public class LockException extends RuntimeException{public LockException(String message) {super(message);}public LockException(String message, Throwable t) {super(message, t);}}SpringBoot启动的Application类
package com.example.jedis;import cn.hutool.core.date.StopWatch;
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.scheduling.annotation.EnableAsync;
import org.springframework.scheduling.annotation.EnableScheduling;import javax.annotation.PreDestroy;
import javax.annotation.Resource;@SpringBootApplication
@EnableScheduling
@EnableAsync
@Slf4j
public class SpringbootJedisApplication {@ResourceRedisConnectionFactory factory;public static void main(String[] args) {StopWatch stopWatch = new StopWatch();stopWatch.start("springbootJedis");SpringApplication.run(SpringbootJedisApplication.class, args);stopWatch.stop();log.info("Springboot项目启动成功时间:{}ms \n", stopWatch.getTotalTimeMillis());log.info(stopWatch.prettyPrint());}@PreDestroypublic void flushDB() {factory.getConnection().flushDb();}}上面的逻辑已经基本实现了一款分布式锁，也可以加一个自定义注解来实现
package com.example.jedis.common;import java.lang.annotation.*;@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Lock {String lockKey();String requestId();int expire() default 30;int timeout() default 1;}自定义一个切面类，实现业务处理
package com.example.jedis.common;import lombok.extern.slf4j.Slf4j;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
import org.springframework.stereotype.Component;import javax.annotation.Resource;
import java.lang.reflect.Method;
import java.util.concurrent.Future;@Component
@Aspect
@Slf4j
public class WatchDog {@Resourceprivate JedisLockTemplate jedisLockTemplate;@Resourceprivate ThreadPoolTaskExecutor executor;@Around("@annotation(Lock)")public Object proxy (ProceedingJoinPoint joinPoint) throws Throwable {MethodSignature methodSignature = (MethodSignature) joinPoint.getSignature();Method method = methodSignature.getMethod();Lock lock = method.getAnnotation(Lock.class);boolean acquire = jedisLockTemplate.acquire(lock.lockKey(), lock.requestId(), lock.expire(), lock.timeout());if (!acquire)throw new LockException("获取锁失败!");Future<Object> future = executor.submit(() -> {try {return joinPoint.proceed();} catch (Throwable e) {log.error("任务执行错误:{}", e);jedisLockTemplate.release(lock.lockKey(), lock.requestId());throw new RuntimeException("任务执行错误");} finally {jedisLockTemplate.release(lock.lockKey(), lock.requestId());}});return future.get();}}写一个测试Controller类，开始用SpringBoot测试类的，但是发现有时候还是经常出现一些连接超时情况，这个可能是框架兼容的bug
package com.example.jedis.controller;import com.example.jedis.common.JedisLockTemplate;
import com.example.jedis.common.Lock;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.stream.IntStream;@RestController
@Slf4j
public class TestController {private static final String REDIS_KEY = "test:lock";@Autowiredprivate JedisLockTemplate jedisLockTemplate;@GetMapping("test")public void test(@RequestParam("threadNum")Integer threadNum) throws InterruptedException {CountDownLatch countDownLatch = new CountDownLatch(threadNum);IntStream.range(0, threadNum).forEach(e->{new Thread(new RunnableTask(countDownLatch)).start();});countDownLatch.await();}@GetMapping("testLock")@Lock(lockKey = "test:api", requestId = "123", expire = 5, timeout = 3)public void testLock() throws InterruptedException {doSomeThing();}class RunnableTask implements Runnable {CountDownLatch countDownLatch;public RunnableTask(CountDownLatch countDownLatch) {this.countDownLatch = countDownLatch;}@Overridepublic void run() {redisLock();countDownLatch.countDown();}}private void redisLock() {String requestId = getRequestId();Boolean lock = jedisLockTemplate.acquire(REDIS_KEY, requestId, 5, 3);if (lock) {try {doSomeThing();} catch (Exception e) {jedisLockTemplate.release(REDIS_KEY, requestId);} finally {jedisLockTemplate.release(REDIS_KEY, requestId);}} else {log.warn("获取锁失败!");}}private void doSomeThing() throws InterruptedException {log.info("do some thing");Thread.sleep(15 * 1000);}private String getRequestId() {String str="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";Random random=new Random();StringBuffer sb=new StringBuffer();for(int i=0;i<32;i++){int number=random.nextInt(62);sb.append(str.charAt(number));}return sb.toString();}}# 模拟100个并发请求
curl http://127.0.0.1:8080/springboot-jedis/test?threadNum=100
项目启动出现这种问题，有可能是在SpringBoot的junit测试类里测试的，setnxex方法加上synchronize同步锁
java.net.SocketTimeoutException: Read timed out
Could not get a resource from the pool
总结：本文基于jedis、jua脚本实现一个分布式锁，redis分布式锁是基于AP模式的，所以效率还是比较快的，但是不能保证分布式的CP模式，如果要保证高一致性，可以选用其它分布式锁方案，本文还考虑到长事务的情况，使用watchdog对key进行续期