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
-
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。
-
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：
-
JDK 1.8
-
SpringBoot 2.2.1
-
Maven 3.2+
-
Mysql 8.0.26
-
spring-boot-starter-data-redis 2.2.1
-
jedis3.1.0
-
开发工具
-
IntelliJ IDEA
-
smartGit
-
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 {
@Override
public 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 exception
log.error("sockTimeout exception:{}", e);
}
else if (cause instanceof InterruptedException) {
// ignore exception
log.error("Interrupted exception:{}", e);
}
else {
log.error("lock acquire exception:{}", e);
}
throw new LockException(e.getMessage(), e);
}
return false;
}
@Override
public 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;
@Autowired
private JedisTemplate jedisTemplate;
private ScheduledThreadPoolExecutor scheduledExecutorService;
@Override
public void afterPropertiesSet() throws Exception {
this.UNLOCK_LUA = jedisTemplate.scriptLoad(UNLOCK_LUA);
this.WATCH_DOG_LUA = jedisTemplate.scriptLoad(WATCH_DOG_LUA);
scheduledExecutorService = new ScheduledThreadPoolExecutor(1);
}
@Override
public boolean doAcquire(String lockKey, String requestId, int expire) {
return jedisTemplate.setnxex(lockKey, requestId, expire);
}
@Override
public 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;
}
@Override
public 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;
}
@Override
public 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 {
@Resource
private JedisPool jedisPool;
private Jedis jedis;
public JedisTemplate() {
}
@Override
public 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 {
@Resource
RedisConnectionFactory 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());
}
@PreDestroy
public 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 {
@Resource
private JedisLockTemplate jedisLockTemplate;
@Resource
private 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";
@Autowired
private 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;
}
@Override
public 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
