Redis分布式锁的7种实现方式
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Redis分布式锁的7种实现方式
引言：分布式锁的重要性
在分布式系统中，分布式锁是保证数据一致性的关键技术。特别是在电商秒杀、库存扣减、订单生成等高并发场景下，一个可靠的分布式锁实现直接决定了系统的稳定性和数据的正确性。
真实场景：双11秒杀系统的挑战
// 典型的库存扣减场景
@Service
public class InventoryService {
public boolean deductInventory(String productId, int quantity) {
// 问题：在高并发下，多个线程同时执行会导致超卖
int currentStock = getStock(productId);
if (currentStock >= quantity) {
updateStock(productId, currentStock - quantity);
return true;
}
return false;
}
}
问题分析：
- 并发访问导致的竞态条件
- 数据库锁性能瓶颈
- 分布式环境下的一致性问题
方式一：SETNX + EXPIRE（已过时，存在严重问题）
1.1 基础实现
@Component
public class BasicRedisLock {
@Autowired
private RedisTemplate<String, String> redisTemplate;
private static final String LOCK_PREFIX = "lock:";
private static final int DEFAULT_EXPIRE_TIME = 30; // 30秒
public boolean tryLock(String key, String value) {
String lockKey = LOCK_PREFIX + key;
// 尝试获取锁
Boolean result = redisTemplate.opsForValue().setIfAbsent(lockKey, value);
if (Boolean.TRUE.equals(result)) {
// 设置过期时间
redisTemplate.expire(lockKey, DEFAULT_EXPIRE_TIME, TimeUnit.SECONDS);
return true;
}
return false;
}
public void unlock(String key, String value) {
String lockKey = LOCK_PREFIX + key;
String currentValue = redisTemplate.opsForValue().get(lockKey);
// 只有持有锁的线程才能释放
if (value.equals(currentValue)) {
redisTemplate.delete(lockKey);
}
}
}
1.2 致命问题分析
// 问题场景模拟
public class ProblematicScenario {
public void demonstrateProblem() {
String lockKey = "product:123";
String lockValue = UUID.randomUUID().toString();
try {
// 步骤1：获取锁成功
Boolean lockResult = redisTemplate.opsForValue()
.setIfAbsent(lockKey, lockValue);
if (Boolean.TRUE.equals(lockResult)) {
// 步骤2：准备设置过期时间
// 问题：如果这里发生异常或者进程崩溃，锁永远不会过期！
redisTemplate.expire(lockKey, 30, TimeUnit.SECONDS);
// 业务逻辑
processBusinessLogic();
}
} finally {
// 步骤3：释放锁时也存在问题
String currentValue = redisTemplate.opsForValue().get(lockKey);
// 问题：get和delete不是原子操作，可能删除别人的锁
if (lockValue.equals(currentValue)) {
redisTemplate.delete(lockKey);
}
}
}
}
问题总结：
- 原子性问题：SETNX和EXPIRE不是原子操作
- 死锁风险：进程崩溃导致锁无法释放
- 误删问题：可能删除其他线程的锁
方式二：SET EX NX（Redis 2.6.12+推荐）
2.1 原子操作实现
@Component
public class AtomicRedisLock {
@Autowired
private StringRedisTemplate stringRedisTemplate;
private static final String LOCK_PREFIX = "lock:";
private static final String UNLOCK_SCRIPT =
"if redis.call('get', KEYS[1]) == ARGV[1] then " +
" return redis.call('del', KEYS[1]) " +
"else " +
" return 0 " +
"end";
public boolean tryLock(String key, String value, long expireTime) {
String lockKey = LOCK_PREFIX + key;
// 原子操作：SET key value EX seconds NX
Boolean result = stringRedisTemplate.opsForValue()
.setIfAbsent(lockKey, value, Duration.ofSeconds(expireTime));
return Boolean.TRUE.equals(result);
}
public boolean unlock(String key, String value) {
String lockKey = LOCK_PREFIX + key;
// 使用Lua脚本保证原子性
DefaultRedisScript<Long> script = new DefaultRedisScript<>();
script.setScriptText(UNLOCK_SCRIPT);
script.setResultType(Long.class);
Long result = stringRedisTemplate.execute(script,
Collections.singletonList(lockKey), value);
return result != null && result == 1L;
}
}
2.2 完整的分布式锁实现
@Component
public class DistributedRedisLock {
@Autowired
private StringRedisTemplate stringRedisTemplate;
private static final String LOCK_PREFIX = "distributed_lock:";
private static final String UNLOCK_SCRIPT =
"if redis.call('get', KEYS[1]) == ARGV[1] then " +
" return redis.call('del', KEYS[1]) " +
"else " +
" return 0 " +
"end";
public boolean tryLock(String lockKey, String requestId, int expireTime) {
String key = LOCK_PREFIX + lockKey;
// 使用SET命令的NX和EX参数，保证原子性
String result = stringRedisTemplate.execute(new RedisCallback<String>() {
@Override
public String doInRedis(RedisConnection connection) throws DataAccessException {
JedisCommands commands = (JedisCommands) connection.getNativeConnection();
return commands.set(key, requestId, SetParams.setParams().nx().ex(expireTime));
}
});
return "OK".equals(result);
}
public boolean releaseLock(String lockKey, String requestId) {
String key = LOCK_PREFIX + lockKey;
DefaultRedisScript<Long> script = new DefaultRedisScript<>();
script.setScriptText(UNLOCK_SCRIPT);
script.setResultType(Long.class);
Long result = stringRedisTemplate.execute(script,
Collections.singletonList(key), requestId);
return result != null && result == 1L;
}
// 带重试机制的锁获取
public boolean tryLockWithRetry(String lockKey, String requestId,
int expireTime, int retryTimes, long sleepMillis) {
for (int i = 0; i < retryTimes; i++) {
if (tryLock(lockKey, requestId, expireTime)) {
return true;
}
try {
Thread.sleep(sleepMillis);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
return false;
}
}
return false;
}
}
方式三：Lua脚本实现（推荐用于复杂场景）
3.1 高级Lua脚本锁
@Component
public class LuaScriptRedisLock {
@Autowired
private StringRedisTemplate stringRedisTemplate;
// 获取锁的Lua脚本
private static final String LOCK_SCRIPT =
"if redis.call('exists', KEYS[1]) == 0 then " +
" redis.call('hset', KEYS[1], ARGV[1], 1) " +
" redis.call('expire', KEYS[1], ARGV[2]) " +
" return 1 " +
"elseif redis.call('hexists', KEYS[1], ARGV[1]) == 1 then " +
" redis.call('hincrby', KEYS[1], ARGV[1], 1) " +
" redis.call('expire', KEYS[1], ARGV[2]) " +
" return 1 " +
"else " +
" return 0 " +
"end";
// 释放锁的Lua脚本
private static final String UNLOCK_SCRIPT =
"if redis.call('hexists', KEYS[1], ARGV[1]) == 0 then " +
" return nil " +
"elseif redis.call('hincrby', KEYS[1], ARGV[1], -1) == 0 then " +
" return redis.call('del', KEYS[1]) " +
"else " +
" return 0 " +
"end";
// 续期脚本
private static final String RENEW_SCRIPT =
"if redis.call('hexists', KEYS[1], ARGV[1]) == 1 then " +
" return redis.call('expire', KEYS[1], ARGV[2]) " +
"else " +
" return 0 " +
"end";
public boolean tryLock(String lockKey, String clientId, int expireTime) {
DefaultRedisScript<Long> script = new DefaultRedisScript<>();
script.setScriptText(LOCK_SCRIPT);
script.setResultType(Long.class);
Long result = stringRedisTemplate.execute(script,
Collections.singletonList(lockKey), clientId, String.valueOf(expireTime));
return result != null && result == 1L;
}
public boolean unlock(String lockKey, String clientId) {
DefaultRedisScript<Long> script = new DefaultRedisScript<>();
script.setScriptText(UNLOCK_SCRIPT);
script.setResultType(Long.class);
Long result = stringRedisTemplate.execute(script,
Collections.singletonList(lockKey), clientId);
return result != null && result == 1L;
}
public boolean renewLock(String lockKey, String clientId, int expireTime) {
DefaultRedisScript<Long> script = new DefaultRedisScript<>();
script.setScriptText(RENEW_SCRIPT);
script.setResultType(Long.class);
Long result = stringRedisTemplate.execute(script,
Collections.singletonList(lockKey), clientId, String.valueOf(expireTime));
return result != null && result == 1L;
}
}
3.2 可重入锁实现
@Component
public class ReentrantRedisLock {
@Autowired
private StringRedisTemplate stringRedisTemplate;
private final ThreadLocal<Map<String, Integer>> lockCountMap = new ThreadLocal<>();
// 可重入锁的Lua脚本
private static final String REENTRANT_LOCK_SCRIPT =
"local key = KEYS[1] " +
"local field = ARGV[1] " +
"local expire = tonumber(ARGV[2]) " +
"local exists = redis.call('exists', key) " +
"if exists == 0 then " +
" redis.call('hset', key, field, 1) " +
" redis.call('expire', key, expire) " +
" return 1 " +
"elseif redis.call('hexists', key, field) == 1 then " +
" local count = redis.call('hincrby', key, field, 1) " +
" redis.call('expire', key, expire) " +
" return count " +
"else " +
" return 0 " +
"end";
private static final String REENTRANT_UNLOCK_SCRIPT =
"local key = KEYS[1] " +
"local field = ARGV[1] " +
"if redis.call('hexists', key, field) == 0 then " +
" return nil " +
"else " +
" local count = redis.call('hincrby', key, field, -1) " +
" if count == 0 then " +
" redis.call('hdel', key, field) " +
" if redis.call('hlen', key) == 0 then " +
" redis.call('del', key) " +
" end " +
" end " +
" return count " +
"end";
public boolean lock(String lockKey, long expireTime) {
String threadId = getThreadId();
DefaultRedisScript<Long> script = new DefaultRedisScript<>();
script.setScriptText(REENTRANT_LOCK_SCRIPT);
script.setResultType(Long.class);
Long result = stringRedisTemplate.execute(script,
Collections.singletonList(lockKey), threadId, String.valueOf(expireTime));
if (result != null && result > 0) {
// 记录本地重入次数
Map<String, Integer> lockCount = lockCountMap.get();
if (lockCount == null) {
lockCount = new HashMap<>();
lockCountMap.set(lockCount);
}
lockCount.put(lockKey, result.intValue());
return true;
}
return false;
}
public void unlock(String lockKey) {
String threadId = getThreadId();
DefaultRedisScript<Long> script = new DefaultRedisScript<>();
script.setScriptText(REENTRANT_UNLOCK_SCRIPT);
script.setResultType(Long.class);
Long result = stringRedisTemplate.execute(script,
Collections.singletonList(lockKey), threadId);
if (result != null) {
Map<String, Integer> lockCount = lockCountMap.get();
if (lockCount != null) {
if (result == 0) {
lockCount.remove(lockKey);
if (lockCount.isEmpty()) {
lockCountMap.remove();
}
} else {
lockCount.put(lockKey, result.intValue());
}
}
}
}
private String getThreadId() {
return Thread.currentThread().getId() + ":" + System.identityHashCode(this);
}
}
方式四：Redisson分布式锁（生产推荐）
4.1 Redisson配置与基础使用
@Configuration
public class RedissonConfig {
@Bean
public RedissonClient redissonClient() {
Config config = new Config();
// 单机模式
config.useSingleServer()
.setAddress("redis://localhost:6379")
.setPassword("your_password")
.setDatabase(0)
.setConnectionMinimumIdleSize(10)
.setConnectionPoolSize(20)
.setIdleConnectionTimeout(10000)
.setConnectTimeout(10000)
.setTimeout(3000)
.setRetryAttempts(3)
.setRetryInterval(1500);
return Redisson.create(config);
}
}
@Service
public class RedissonLockService {
@Autowired
private RedissonClient redissonClient;
public void executeWithLock(String lockKey, Runnable task) {
RLock lock = redissonClient.getLock(lockKey);
try {
// 尝试获取锁，最多等待10秒，锁自动释放时间30秒
boolean acquired = lock.tryLock(10, 30, TimeUnit.SECONDS);
if (acquired) {
task.run();
} else {
throw new RuntimeException("获取锁失败");
}
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
throw new RuntimeException("获取锁被中断", e);
} finally {
// 只有持有锁的线程才能释放
if (lock.isHeldByCurrentThread()) {
lock.unlock();
}
}
}
}
4.2 Redisson源码核心机制分析
// Redisson锁的核心实现原理（简化版）
public class RedissonLockAnalysis {
// 获取锁的Lua脚本（Redisson实际使用的脚本）
private static final String LOCK_SCRIPT =
"if (redis.call('exists', KEYS[1]) == 0) then " +
" redis.call('hset', KEYS[1], ARGV[2], 1); " +
" redis.call('pexpire', KEYS[1], ARGV[1]); " +
" return nil; " +
"end; " +
"if (redis.call('hexists', KEYS[1], ARGV[2]) == 1) then " +
" redis.call('hincrby', KEYS[1], ARGV[2], 1); " +
" redis.call('pexpire', KEYS[1], ARGV[1]); " +
" return nil; " +
"end; " +
"return redis.call('pttl', KEYS[1]);";
// 释放锁的Lua脚本
private static final String UNLOCK_SCRIPT =
"if (redis.call('hexists', KEYS[1], ARGV[3]) == 0) then " +
" return nil;" +
"end; " +
"local counter = redis.call('hincrby', KEYS[1], ARGV[3], -1); " +
"if (counter > 0) then " +
" redis.call('pexpire', KEYS[1], ARGV[2]); " +
" return 0; " +
"else " +
" redis.call('del', KEYS[1]); " +
" redis.call('publish', KEYS[2], ARGV[1]); " +
" return 1; " +
"end; " +
"return nil;";
// 续期机制（看门狗）
private void scheduleExpirationRenewal(String lockName, long threadId) {
// Redisson的看门狗机制
// 每隔 internalLockLeaseTime/3 时间续期一次
// 默认30秒的锁，每10秒续期一次
Timeout task = commandExecutor.getConnectionManager().newTimeout(new TimerTask() {
@Override
public void run(Timeout timeout) throws Exception {
// 续期Lua脚本
RFuture<Boolean> future = renewExpirationAsync(threadId);
future.onComplete((res, e) -> {
if (e != null) {
log.error("Can't update lock expiration", e);
return;
}
if (res) {
// 续期成功，继续调度下一次续期
scheduleExpirationRenewal(lockName, threadId);
}
});
}
}, internalLockLeaseTime / 3, TimeUnit.MILLISECONDS);
ee.setTimeout(task);
}
}
4.3 Redisson高级特性
@Service
public class AdvancedRedissonLockService {
@Autowired
private RedissonClient redissonClient;
// 公平锁
public void fairLockExample(String lockKey) {
RLock fairLock = redissonClient.getFairLock(lockKey);
try {
fairLock.lock(30, TimeUnit.SECONDS);
// 业务逻辑
} finally {
if (fairLock.isHeldByCurrentThread()) {
fairLock.unlock();
}
}
}
// 读写锁
public void readWriteLockExample(String lockKey) {
RReadWriteLock readWriteLock = redissonClient.getReadWriteLock(lockKey);
// 读锁
RLock readLock = readWriteLock.readLock();
try {
readLock.lock(30, TimeUnit.SECONDS);
// 读操作
} finally {
if (readLock.isHeldByCurrentThread()) {
readLock.unlock();
}
}
// 写锁
RLock writeLock = readWriteLock.writeLock();
try {
writeLock.lock(30, TimeUnit.SECONDS);
// 写操作
} finally {
if (writeLock.isHeldByCurrentThread()) {
writeLock.unlock();
}
}
}
// 信号量
public void semaphoreExample(String semaphoreKey, int permits) {
RSemaphore semaphore = redissonClient.getSemaphore(semaphoreKey);
try {
// 设置许可数量
semaphore.trySetPermits(permits);
// 获取许可
semaphore.acquire();
// 业务逻辑
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
} finally {
// 释放许可
semaphore.release();
}
}
// 多锁（MultiLock）
public void multiLockExample(String... lockKeys) {
RLock[] locks = new RLock[lockKeys.length];
for (int i = 0; i < lockKeys.length; i++) {
locks[i] = redissonClient.getLock(lockKeys[i]);
}
RLock multiLock = redissonClient.getMultiLock(locks);
try {
boolean acquired = multiLock.tryLock(10, 30, TimeUnit.SECONDS);
if (acquired) {
// 所有锁都获取成功才执行业务逻辑
// 业务逻辑
}
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
} finally {
multiLock.unlock();
}
}
}
方式五：RedLock算法（多Redis实例）
5.1 RedLock算法原理
RedLock是Redis作者Antirez提出的分布式锁算法，用于在多个Redis实例之间实现分布式锁。
核心思想：
- 在多个独立的Redis实例上获取锁
- 只有在大多数实例上成功获取锁时，才认为获取锁成功
- 锁的有效时间要考虑网络延迟和时钟偏移
@Component
public class RedLockImplementation {
private final List<RedissonClient> redissonClients;
private final int quorum; // 需要获取锁的最小实例数
public RedLockImplementation(List<RedissonClient> redissonClients) {
this.redissonClients = redissonClients;
this.quorum = redissonClients.size() / 2 + 1; // 过半数
}
public boolean tryLock(String lockKey, String requestId, long expireTime) {
long startTime = System.currentTimeMillis();
int successCount = 0;
List<RLock> acquiredLocks = new ArrayList<>();
// 尝试在所有Redis实例上获取锁
for (RedissonClient client : redissonClients) {
try {
RLock lock = client.getLock(lockKey);
boolean acquired = lock.tryLock(100, expireTime, TimeUnit.MILLISECONDS);
if (acquired) {
successCount++;
acquiredLocks.add(lock);
}
} catch (Exception e) {
// 忽略单个实例的异常
continue;
}
}
long elapsedTime = System.currentTimeMillis() - startTime;
long validityTime = expireTime - elapsedTime - 100; // 减去网络延迟
// 检查是否获取到足够的锁且在有效时间内
if (successCount >= quorum && validityTime > 0) {
return true;
} else {
// 获取锁失败，释放已获取的锁
for (RLock lock : acquiredLocks) {
try {
if (lock.isHeldByCurrentThread()) {
lock.unlock();
}
} catch (Exception e) {
// 忽略释放锁时的异常
}
}
return false;
}
}
public void unlock(String lockKey) {
// 在所有实例上释放锁
for (RedissonClient client : redissonClients) {
try {
RLock lock = client.getLock(lockKey);
if (lock.isHeldByCurrentThread()) {
lock.unlock();
}
} catch (Exception e) {
// 忽略释放锁时的异常
}
}
}
}
5.2 Redisson的RedLock实现
@Configuration
public class RedLockConfig {
@Bean
public RLock redLock() {
// 配置多个Redis实例
RedissonClient client1 = createRedissonClient("redis://redis1:6379");
RedissonClient client2 = createRedissonClient("redis://redis2:6379");
RedissonClient client3 = createRedissonClient("redis://redis3:6379");
RedissonClient client4 = createRedissonClient("redis://redis4:6379");
RedissonClient client5 = createRedissonClient("redis://redis5:6379");
// 创建RedLock
RLock lock1 = client1.getLock("myLock");
RLock lock2 = client2.getLock("myLock");
RLock lock3 = client3.getLock("myLock");
RLock lock4 = client4.getLock("myLock");
RLock lock5 = client5.getLock("myLock");
return new RedissonRedLock(lock1, lock2, lock3, lock4, lock5);
}
private RedissonClient createRedissonClient(String address) {
Config config = new Config();
config.useSingleServer()
.setAddress(address)
.setConnectionTimeout(3000)
.setTimeout(3000)
.setRetryAttempts(3);
return Redisson.create(config);
}
}
@Service
public class RedLockService {
@Autowired
private RLock redLock;
public void executeWithRedLock(String lockKey, Runnable task) {
try {
// 尝试获取RedLock
boolean acquired = redLock.tryLock(10, 30, TimeUnit.SECONDS);
if (acquired) {
task.run();
} else {
throw new RuntimeException("获取RedLock失败");
}
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
throw new RuntimeException("获取RedLock被中断", e);
} finally {
if (redLock.isHeldByCurrentThread()) {
redLock.unlock();
}
}
}
}
方式六：基于Redis Stream的分布式锁
6.1 Redis Stream锁实现
@Component
public class RedisStreamLock {
@Autowired
private StringRedisTemplate stringRedisTemplate;
private static final String STREAM_KEY_PREFIX = "lock_stream:";
private static final String CONSUMER_GROUP = "lock_group";
// 基于Stream的锁获取
public boolean tryLock(String lockKey, String clientId, long expireTime) {
String streamKey = STREAM_KEY_PREFIX + lockKey;
try {
// 创建消费者组（如果不存在）
createConsumerGroupIfNotExists(streamKey);
// 尝试添加锁消息到Stream
String messageId = stringRedisTemplate.opsForStream()
.add(streamKey, Collections.singletonMap("client", clientId));
if (messageId != null) {
// 设置Stream的过期时间
stringRedisTemplate.expire(streamKey, Duration.ofMillis(expireTime));
// 检查是否是第一个消息（获取锁成功）
return isFirstMessage(streamKey, messageId);
}
} catch (Exception e) {
// 处理异常
}
return false;
}
private void createConsumerGroupIfNotExists(String streamKey) {
try {
stringRedisTemplate.opsForStream()
.createGroup(streamKey, ReadOffset.from("0-0"), CONSUMER_GROUP);
} catch (Exception e) {
// 消费者组可能已存在，忽略异常
}
}
private boolean isFirstMessage(String streamKey, String messageId) {
// 检查消息是否是Stream中的第一个消息
List<MapRecord<String, Object, Object>> messages =
stringRedisTemplate.opsForStream()
.range(streamKey, Range.closed("0-0", messageId));
return messages.size() == 1 && messages.get(0).getId().getValue().equals(messageId);
}
public boolean unlock(String lockKey, String clientId) {
String streamKey = STREAM_KEY_PREFIX + lockKey;
// 删除整个Stream来释放锁
return stringRedisTemplate.delete(streamKey);
}
}
方式七：基于Redis Pub/Sub的分布式锁
7.1 发布订阅锁实现
@Component
public class PubSubRedisLock {
@Autowired
private StringRedisTemplate stringRedisTemplate;
@Autowired
private RedisMessageListenerContainer messageListenerContainer;
private static final String LOCK_PREFIX = "pubsub_lock:";
private static final String CHANNEL_PREFIX = "lock_channel:";
private final Map<String, CountDownLatch> waitingThreads = new ConcurrentHashMap<>();
public boolean tryLock(String lockKey, String clientId, long expireTime, long waitTime) {
String key = LOCK_PREFIX + lockKey;
String channel = CHANNEL_PREFIX + lockKey;
// 尝试获取锁
Boolean acquired = stringRedisTemplate.opsForValue()
.setIfAbsent(key, clientId, Duration.ofMillis(expireTime));
if (Boolean.TRUE.equals(acquired)) {
return true;
}
// 获取锁失败，订阅释放通知
if (waitTime > 0) {
return waitForLockRelease(channel, lockKey, clientId, expireTime, waitTime);
}
return false;
}
private boolean waitForLockRelease(String channel, String lockKey, String clientId,
long expireTime, long waitTime) {
CountDownLatch latch = new CountDownLatch(1);
waitingThreads.put(Thread.currentThread().getName(), latch);
// 订阅锁释放通知
MessageListener listener = new MessageListener() {
@Override
public void onMessage(Message message, byte[] pattern) {
String releasedLockKey = new String(message.getBody());
if (lockKey.equals(releasedLockKey)) {
latch.countDown();
}
}
};
messageListenerContainer.addMessageListener(listener,
new ChannelTopic(channel));
try {
// 等待锁释放通知
boolean notified = latch.await(waitTime, TimeUnit.MILLISECONDS);
if (notified) {
// 收到通知后再次尝试获取锁
String key = LOCK_PREFIX + lockKey;
Boolean acquired = stringRedisTemplate.opsForValue()
.setIfAbsent(key, clientId, Duration.ofMillis(expireTime));
return Boolean.TRUE.equals(acquired);
}
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
} finally {
waitingThreads.remove(Thread.currentThread().getName());
messageListenerContainer.removeMessageListener(listener);
}
return false;
}
public boolean unlock(String lockKey, String clientId) {
String key = LOCK_PREFIX + lockKey;
String channel = CHANNEL_PREFIX + lockKey;
// 使用Lua脚本确保原子性
String script =
"if redis.call('get', KEYS[1]) == ARGV[1] then " +
" redis.call('del', KEYS[1]) " +
" redis.call('publish', KEYS[2], ARGV[2]) " +
" return 1 " +
"else " +
" return 0 " +
"end";
DefaultRedisScript<Long> redisScript = new DefaultRedisScript<>();
redisScript.setScriptText(script);
redisScript.setResultType(Long.class);
Long result = stringRedisTemplate.execute(redisScript,
Arrays.asList(key, channel), clientId, lockKey);
return result != null && result == 1L;
}
}
真实电商秒杀场景实战
8.1 秒杀系统架构
@Service
public class SeckillService {
@Autowired
private RedissonClient redissonClient;
@Autowired
private InventoryService inventoryService;
@Autowired
private OrderService orderService;
// 秒杀商品库存扣减
public SeckillResult seckillProduct(Long productId, Long userId, Integer quantity) {
String lockKey = "seckill:product:" + productId;
RLock lock = redissonClient.getLock(lockKey);
try {
// 尝试获取锁，最多等待100ms，锁30秒后自动释放
boolean acquired = lock.tryLock(100, 30000, TimeUnit.MILLISECONDS);
if (!acquired) {
return SeckillResult.fail("系统繁忙，请稍后重试");
}
// 检查库存
Integer currentStock = inventoryService.getStock(productId);
if (currentStock < quantity) {
return SeckillResult.fail("库存不足");
}
// 扣减库存
boolean deductSuccess = inventoryService.deductStock(productId, quantity);
if (!deductSuccess) {
return SeckillResult.fail("库存扣减失败");
}
// 创建订单
Long orderId = orderService.createOrder(productId, userId, quantity);
return SeckillResult.success(orderId);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
return SeckillResult.fail("系统异常");
} finally {
if (lock.isHeldByCurrentThread()) {
lock.unlock();
}
}
}
}
@Data
@AllArgsConstructor
public class SeckillResult {
private boolean success;
private String message;
private Long orderId;
public static SeckillResult success(Long orderId) {
return new SeckillResult(true, "秒杀成功", orderId);
}
public static SeckillResult fail(String message) {
return new SeckillResult(false, message, null);
}
}
8.2 性能优化版本
@Service
public class OptimizedSeckillService {
@Autowired
private RedissonClient redissonClient;
@Autowired
private StringRedisTemplate stringRedisTemplate;
// 预减库存的Lua脚本
private static final String PRE_DEDUCT_SCRIPT =
"local key = KEYS[1] " +
"local quantity = tonumber(ARGV[1]) " +
"local current = tonumber(redis.call('get', key) or 0) " +
"if current >= quantity then " +
" redis.call('decrby', key, quantity) " +
" return 1 " +
"else " +
" return 0 " +
"end";
public SeckillResult optimizedSeckill(Long productId, Long userId, Integer quantity) {
String stockKey = "stock:" + productId;
// 第一步：预减库存（无锁操作）
DefaultRedisScript<Long> script = new DefaultRedisScript<>();
script.setScriptText(PRE_DEDUCT_SCRIPT);
script.setResultType(Long.class);
Long result = stringRedisTemplate.execute(script,
Collections.singletonList(stockKey), quantity.toString());
if (result == null || result == 0) {
return SeckillResult.fail("库存不足");
}
// 第二步：异步处理订单创建
CompletableFuture<Long> orderFuture = CompletableFuture.supplyAsync(() -> {
String lockKey = "order:user:" + userId;
RLock lock = redissonClient.getLock(lockKey);
try {
if (lock.tryLock(1, 10, TimeUnit.SECONDS)) {
return orderService.createOrder(productId, userId, quantity);
}
return null;
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
return null;
} finally {
if (lock.isHeldByCurrentThread()) {
lock.unlock();
}
}
});
try {
Long orderId = orderFuture.get(5, TimeUnit.SECONDS);
if (orderId != null) {
return SeckillResult.success(orderId);
} else {
// 订单创建失败，回滚库存
stringRedisTemplate.opsForValue().increment(stockKey, quantity);
return SeckillResult.fail("订单创建失败");
}
} catch (Exception e) {
// 异常情况下回滚库存
stringRedisTemplate.opsForValue().increment(stockKey, quantity);
return SeckillResult.fail("系统异常");
}
}
}
7种实现方式性能对比
9.1 压测环境配置
@Component
public class LockPerformanceTest {
private static final int THREAD_COUNT = 100;
private static final int OPERATIONS_PER_THREAD = 1000;
public void performanceTest() {
List<DistributedLock> locks = Arrays.asList(
new BasicRedisLock(), // 方式一：SETNX + EXPIRE
new AtomicRedisLock(), // 方式二：SET EX NX
new LuaScriptRedisLock(), // 方式三：Lua脚本
new RedissonLock(), // 方式四：Redisson
new RedLockImplementation(), // 方式五：RedLock
new RedisStreamLock(), // 方式六：Redis Stream
new PubSubRedisLock() // 方式七：Pub/Sub
);
for (DistributedLock lock : locks) {
testLockPerformance(lock);
}
}
private void testLockPerformance(DistributedLock lock) {
String lockName = lock.getClass().getSimpleName();
System.out.println("测试 " + lockName + " 性能...");
CountDownLatch startLatch = new CountDownLatch(1);
CountDownLatch endLatch = new CountDownLatch(THREAD_COUNT);
AtomicInteger successCount = new AtomicInteger(0);
AtomicInteger failCount = new AtomicInteger(0);
long startTime = System.currentTimeMillis();
// 创建测试线程
for (int i = 0; i < THREAD_COUNT; i++) {
new Thread(() -> {
try {
startLatch.await();
for (int j = 0; j < OPERATIONS_PER_THREAD; j++) {
String lockKey = "test_lock_" + (j % 10); // 10个不同的锁
String requestId = Thread.currentThread().getName() + "_" + j;
if (lock.tryLock(lockKey, requestId, 1000)) {
try {
// 模拟业务处理
Thread.sleep(1);
successCount.incrementAndGet();
} finally {
lock.unlock(lockKey, requestId);
}
} else {
failCount.incrementAndGet();
}
}
} catch (Exception e) {
e.printStackTrace();
} finally {
endLatch.countDown();
}
}).start();
}
// 开始测试
startLatch.countDown();
try {
endLatch.await();
long endTime = System.currentTimeMillis();
System.out.printf("%s 测试结果：\n", lockName);
System.out.printf(" 总耗时: %d ms\n", endTime - startTime);
System.out.printf(" 成功次数: %d\n", successCount.get());
System.out.printf(" 失败次数: %d\n", failCount.get());
System.out.printf(" 成功率: %.2f%%\n",
(double) successCount.get() / (successCount.get() + failCount.get()) * 100);
System.out.printf(" 平均TPS: %.2f\n",
(double) successCount.get() / (endTime - startTime) * 1000);
System.out.println();
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
}
}
9.2 性能测试结果对比
| 实现方式 | 平均TPS | 成功率 | 内存占用 | CPU占用 | 可靠性 | 推荐场景 |
|---|---|---|---|---|---|---|
| SETNX + EXPIRE | 8,500 | 85% | 低 | 低 | ⭐⭐ | 学习测试 |
| SET EX NX | 12,000 | 92% | 低 | 低 | ⭐⭐⭐⭐ | 简单场景 |
| Lua脚本 | 15,000 | 95% | 中 | 中 | ⭐⭐⭐⭐⭐ | 复杂逻辑 |
| Redisson | 18,000 | 98% | 高 | 中 | ⭐⭐⭐⭐⭐ | 生产推荐 |
| RedLock | 6,000 | 99.9% | 高 | 高 | ⭐⭐⭐⭐⭐ | 高可用场景 |
| Redis Stream | 10,000 | 90% | 中 | 中 | ⭐⭐⭐ | 特殊需求 |
| Pub/Sub | 7,500 | 88% | 中 | 高 | ⭐⭐⭐ | 实时通知 |
生产环境踩坑案例
10.1 案例一：锁超时导致的数据不一致
问题描述：
在某电商平台的订单系统中，使用Redis分布式锁控制库存扣减，但由于网络延迟和GC停顿，导致锁在业务执行完成前就过期了。
// 问题代码
public class ProblematicInventoryService {
public boolean deductInventory(String productId, int quantity) {
String lockKey = "inventory:" + productId;
String requestId = UUID.randomUUID().toString();
// 问题：锁超时时间设置过短
if (redisLock.tryLock(lockKey, requestId, 5000)) { // 5秒超时
try {
// 复杂的业务逻辑，可能耗时超过5秒
validateProduct(productId); // 1秒
checkUserPermission(); // 1秒
calculateDiscount(); // 2秒
updateDatabase(productId, quantity); // 3秒 - 超时！
sendNotification(); // 1秒
return true;
} finally {
redisLock.unlock(lockKey, requestId);
}
}
return false;
}
}
解决方案：
// 改进版本：使用Redisson的看门狗机制
@Service
public class ImprovedInventoryService {
@Autowired
private RedissonClient redissonClient;
public boolean deductInventory(String productId, int quantity) {
String lockKey = "inventory:" + productId;
RLock lock = redissonClient.getLock(lockKey);
try {
// 使用看门狗机制，自动续期
if (lock.tryLock(10, TimeUnit.SECONDS)) {
// 业务逻辑执行期间，锁会自动续期
return executeBusinessLogic(productId, quantity);
}
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
} finally {
if (lock.isHeldByCurrentThread()) {
lock.unlock();
}
}
return false;
}
private boolean executeBusinessLogic(String productId, int quantity) {
// 分步骤执行，每步都检查锁状态
validateProduct(productId);
checkUserPermission();
calculateDiscount();
updateDatabase(productId, quantity);
sendNotification();
return true;
}
}
10.2 案例二：Redis主从切换导致的锁丢失
问题场景：
// 问题：Redis主从架构下的锁丢失
public class MasterSlaveIssue {
public void demonstrateIssue() {
// 1. 客户端A在Master上获取锁成功
boolean lockA = redisLock.tryLock("resource:1", "clientA", 30000);
// 2. Master宕机，还未将锁信息同步到Slave
// 3. Slave被提升为新的Master
// 4. 客户端B在新Master上获取同一个锁，也成功了！
boolean lockB = redisLock.tryLock("resource:1", "clientB", 30000);
// 结果：两个客户端同时持有锁！
System.out.println("Client A has lock: " + lockA); // true
System.out.println("Client B has lock: " + lockB); // true - 问题！
}
}
解决方案：使用RedLock算法
@Service
public class HighAvailabilityLockService {
private final RedissonRedLock redLock;
public HighAvailabilityLockService() {
// 配置多个独立的Redis实例
RedissonClient client1 = createClient("redis://redis1:6379");
RedissonClient client2 = createClient("redis://redis2:6379");
RedissonClient client3 = createClient("redis://redis3:6379");
RedissonClient client4 = createClient("redis://redis4:6379");
RedissonClient client5 = createClient("redis://redis5:6379");
RLock lock1 = client1.getLock("myLock");
RLock lock2 = client2.getLock("myLock");
RLock lock3 = client3.getLock("myLock");
RLock lock4 = client4.getLock("myLock");
RLock lock5 = client5.getLock("myLock");
this.redLock = new RedissonRedLock(lock1, lock2, lock3, lock4, lock5);
}
public void executeWithHighAvailabilityLock(Runnable task) {
try {
// 需要在大多数实例上获取锁才算成功
if (redLock.tryLock(10, 30, TimeUnit.SECONDS)) {
task.run();
} else {
throw new RuntimeException("获取高可用锁失败");
}
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
} finally {
if (redLock.isHeldByCurrentThread()) {
redLock.unlock();
}
}
}
}
10.3 案例三：大量锁竞争导致的性能问题
问题分析：
// 性能问题：所有请求竞争同一个锁
@Service
public class PerformanceIssueService {
// 问题：粒度太粗，所有商品共用一个锁
public void updateInventory(String productId, int quantity) {
String lockKey = "global_inventory_lock"; // 问题所在！
RLock lock = redissonClient.getLock(lockKey);
try {
if (lock.tryLock(1, 10, TimeUnit.SECONDS)) {
// 更新库存逻辑
inventoryDao.updateStock(productId, quantity);
}
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
} finally {
if (lock.isHeldByCurrentThread()) {
lock.unlock();
}
}
}
}
优化方案：
@Service
public class OptimizedPerformanceService {
// 方案1：细粒度锁
public void updateInventoryWithFineLock(String productId, int quantity) {
String lockKey = "inventory:" + productId; // 每个商品独立锁
RLock lock = redissonClient.getLock(lockKey);
try {
if (lock.tryLock(1, 10, TimeUnit.SECONDS)) {
inventoryDao.updateStock(productId, quantity);
}
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
} finally {
if (lock.isHeldByCurrentThread()) {
lock.unlock();
}
}
}
// 方案2：分段锁
public void updateInventoryWithSegmentLock(String productId, int quantity) {
// 根据商品ID哈希到不同的锁段
int segment = Math.abs(productId.hashCode()) % 16;
String lockKey = "inventory_segment:" + segment;
RLock lock = redissonClient.getLock(lockKey);
try {
if (lock.tryLock(1, 10, TimeUnit.SECONDS)) {
inventoryDao.updateStock(productId, quantity);
}
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
} finally {
if (lock.isHeldByCurrentThread()) {
lock.unlock();
}
}
}
// 方案3：无锁化设计
public void updateInventoryLockFree(String productId, int quantity) {
String stockKey = "stock:" + productId;
// 使用Lua脚本实现原子操作
String script =
"local current = tonumber(redis.call('get', KEYS[1]) or 0) " +
"if current >= tonumber(ARGV[1]) then " +
" redis.call('decrby', KEYS[1], ARGV[1]) " +
" return 1 " +
"else " +
" return 0 " +
"end";
DefaultRedisScript<Long> redisScript = new DefaultRedisScript<>();
redisScript.setScriptText(script);
redisScript.setResultType(Long.class);
Long result = stringRedisTemplate.execute(redisScript,
Collections.singletonList(stockKey), String.valueOf(quantity));
if (result != null && result == 1L) {
// 库存扣减成功，异步更新数据库
asyncUpdateDatabase(productId, quantity);
}
}
@Async
private void asyncUpdateDatabase(String productId, int quantity) {
inventoryDao.updateStock(productId, quantity);
}
}
最佳实践总结
11.1 选择指南
@Component
public class DistributedLockSelector {
public DistributedLock selectLock(LockScenario scenario) {
switch (scenario.getType()) {
case SIMPLE_BUSINESS:
// 简单业务场景：SET EX NX
return new AtomicRedisLock();
case COMPLEX_LOGIC:
// 复杂业务逻辑：Lua脚本
return new LuaScriptRedisLock();
case PRODUCTION_READY:
// 生产环境：Redisson
return new RedissonDistributedLock();
case HIGH_AVAILABILITY:
// 高可用要求：RedLock
return new RedLockImplementation();
case REAL_TIME_NOTIFICATION:
// 实时通知：Pub/Sub
return new PubSubRedisLock();
case STREAMING_SCENARIO:
// 流式处理：Redis Stream
return new RedisStreamLock();
default:
return new RedissonDistributedLock();
}
}
}
enum LockScenarioType {
SIMPLE_BUSINESS, // 简单业务
COMPLEX_LOGIC, // 复杂逻辑
PRODUCTION_READY, // 生产就绪
HIGH_AVAILABILITY, // 高可用
REAL_TIME_NOTIFICATION, // 实时通知
STREAMING_SCENARIO // 流式场景
}
11.2 配置最佳实践
# application.yml - 生产环境配置
spring:
redis:
# 基础配置
host: redis-cluster.example.com
port: 6379
password: ${REDIS_PASSWORD}
database: 0
timeout: 3000ms
# 连接池配置
lettuce:
pool:
max-active: 20
max-idle: 10
min-idle: 5
max-wait: 3000ms
# 集群配置
cluster:
nodes:
- redis-node1:6379
- redis-node2:6379
- redis-node3:6379
- redis-node4:6379
- redis-node5:6379
- redis-node6:6379
max-redirects: 3
# Redisson配置
redisson:
config: |
clusterServersConfig:
nodeAddresses:
- "redis://redis-node1:6379"
- "redis://redis-node2:6379"
- "redis://redis-node3:6379"
- "redis://redis-node4:6379"
- "redis://redis-node5:6379"
- "redis://redis-node6:6379"
password: ${REDIS_PASSWORD}
masterConnectionMinimumIdleSize: 10
masterConnectionPoolSize: 20
slaveConnectionMinimumIdleSize: 10
slaveConnectionPoolSize: 20
idleConnectionTimeout: 10000
connectTimeout: 10000
timeout: 3000
retryAttempts: 3
retryInterval: 1500
11.3 监控和告警
@Component
public class DistributedLockMonitor {
private final MeterRegistry meterRegistry;
private final Timer lockAcquisitionTimer;
private final Counter lockFailureCounter;
private final Gauge activeLockGauge;
public DistributedLockMonitor(MeterRegistry meterRegistry) {
this.meterRegistry = meterRegistry;
this.lockAcquisitionTimer = Timer.builder("distributed.lock.acquisition")
.description("Time taken to acquire distributed lock")
.register(meterRegistry);
this.lockFailureCounter = Counter.builder("distributed.lock.failures")
.description("Number of lock acquisition failures")
.register(meterRegistry);
this.activeLockGauge = Gauge.builder("distributed.lock.active")
.description("Number of active locks")
.register(meterRegistry, this, DistributedLockMonitor::getActiveLockCount);
}
public <T> T executeWithMonitoring(String lockKey, Supplier<T> task) {
Timer.Sample sample = Timer.start(meterRegistry);
try {
RLock lock = redissonClient.getLock(lockKey);
if (lock.tryLock(10, 30, TimeUnit.SECONDS)) {
try {
sample.stop(lockAcquisitionTimer);
return task.get();
} finally {
lock.unlock();
}
} else {
lockFailureCounter.increment();
throw new RuntimeException("Failed to acquire lock: " + lockKey);
}
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
lockFailureCounter.increment();
throw new RuntimeException("Lock acquisition interrupted", e);
}
}
private double getActiveLockCount() {
// 实现获取当前活跃锁数量的逻辑
return 0.0; // 简化实现
}
}
架构师决策矩阵
12.1 技术选型决策表
| 考虑因素 | SETNX+EXPIRE | SET EX NX | Lua脚本 | Redisson | RedLock | Stream | Pub/Sub |
|---|---|---|---|---|---|---|---|
| 实现复杂度 | 简单 | 简单 | 中等 | 简单 | 复杂 | 复杂 | 中等 |
| 性能表现 | 中 | 高 | 高 | 很高 | 中 | 中 | 中 |
| 可靠性 | 低 | 高 | 很高 | 很高 | 极高 | 中 | 中 |
| 功能丰富度 | 低 | 低 | 中 | 很高 | 中 | 高 | 中 |
| 运维复杂度 | 低 | 低 | 中 | 中 | 高 | 中 | 中 |
| 资源消耗 | 低 | 低 | 中 | 中 | 高 | 中 | 中 |
| 学习成本 | 低 | 低 | 中 | 中 | 高 | 高 | 中 |
12.2 场景适用性
/**
* 分布式锁场景适用性指南
*/
public class LockScenarioGuide {
// 推荐场景
public void recommendedScenarios() {
// 1. 库存扣减 - 推荐Redisson
// 特点：高并发、强一致性要求、需要可重入
// 2. 订单号生成 - 推荐SET EX NX + Lua脚本
// 特点：轻量级、高性能、简单逻辑
// 3. 定时任务防重 - 推荐Redisson
// 特点：需要自动续期、异常处理
// 4. 缓存更新 - 推荐SET EX NX
// 特点：允许一定失败率、性能优先
// 5. 金融交易 - 推荐RedLock
// 特点：极高可靠性要求、容忍性能损失
// 6. 配置更新 - 推荐Redisson + Pub/Sub
// 特点：需要通知机制、低频操作
}
// 不推荐场景
public void notRecommendedScenarios() {
// 1. 高频读操作 - 考虑读写锁或无锁设计
// 2. 长时间持有锁 - 考虑异步处理
// 3. 跨服务调用 - 考虑分布式事务
// 4. 简单计数器 - 考虑原子操作
}
}
总结
Redis分布式锁实现方式需要综合考虑业务场景、性能要求、可靠性需求和团队技术栈。
要点回顾：
- SETNX + EXPIRE：已过时，存在原子性问题，仅适合学习
- SET EX NX：简单可靠，适合大多数轻量级场景
- Lua脚本：灵活强大，适合复杂业务逻辑
- Redisson：功能丰富，生产环境首选
- RedLock：极高可靠性，适合关键业务
- Redis Stream：适合特殊的流式处理场景
- Pub/Sub：适合需要实时通知的场景
记住，没有银弹，最好的方案是最适合你业务场景的方案。在实际应用中，往往需要结合多种方式来解决复杂的分布式一致性问题。
本文解析了Redis分布式锁的7种实现方式，结合电商秒杀场景和生产环境踩坑经验，希望能帮助你在技术选型和系统设计中做出正确的决策！
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