本文主要是介绍redis缓存 ★代码★ 实战【红锁问题（主从同步）、分布锁性能优化、缓存数据冷热分离、大量缓存重建、双写一致问题】，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
redis缓存实战
- 主从同步时 主节点挂了
- 分布式锁性能提升
- 缓存数据冷热分离问题
- 大量缓存重建问题
- 双写一致问题
- 实战
- 创建数据放入缓存
- 更新数据然后放入缓存（读写锁优化）
- 查询数据
- 1. 判断缓存中是否已经有数据
- 2. 如果没有，则会查数据库（上分布锁）
- 3. 再次查询是否缓存中已经有了（因为排队查询获取锁的时候 可能前面的已经创建好了）
- 4. 如果没有则读写锁 获取数据（因为上面的锁是重入锁，所以在这还要设置一个读写锁）
- 代码
主从同步时 主节点挂了
- redlock解决中出现的问题
- zookeeper解决办法
分布式锁性能提升
- 使用分段锁
- 使用读写锁
缓存数据冷热分离问题
使用锁过期+锁分离
大量缓存重建问题
使用分布锁解决
双写一致问题
使用分布锁解决
实战
创建数据放入缓存
@Transactionalpublic Product create(Product product) {Product productResult = productDao.create(product);redisUtil.set(RedisKeyPrefixConst.PRODUCT_CACHE + productResult.getId(), JSON.toJSONString(productResult),genProductCacheTimeout(), TimeUnit.SECONDS);return productResult;}
更新数据然后放入缓存（读写锁优化）
@Transactionalpublic Product update(Product product) {Product productResult = null;//RLock updateProductLock = redisson.getLock(LOCK_PRODUCT_UPDATE_PREFIX + product.getId());RReadWriteLock readWriteLock = redisson.getReadWriteLock(LOCK_PRODUCT_UPDATE_PREFIX + product.getId());RLock writeLock = readWriteLock.writeLock();writeLock.lock();try {productResult = productDao.update(product);redisUtil.set(RedisKeyPrefixConst.PRODUCT_CACHE + productResult.getId(), JSON.toJSONString(productResult),genProductCacheTimeout(), TimeUnit.SECONDS);productMap.put(RedisKeyPrefixConst.PRODUCT_CACHE + productResult.getId(), product);} finally {writeLock.unlock();}return productResult;}
查询数据
1. 判断缓存中是否已经有数据
2. 如果没有，则会查数据库（上分布锁）
3. 再次查询是否缓存中已经有了（因为排队查询获取锁的时候 可能前面的已经创建好了）
4. 如果没有则读写锁 获取数据（因为上面的锁是重入锁，所以在这还要设置一个读写锁）
public Product get(Long productId) throws InterruptedException {Product product = null;String productCacheKey = RedisKeyPrefixConst.PRODUCT_CACHE + productId;product = getProductFromCache(productCacheKey);if (product != null) {return product;}//DCLRLock hotCacheLock = redisson.getLock(LOCK_PRODUCT_HOT_CACHE_PREFIX + productId);hotCacheLock.lock();//boolean result = hotCacheLock.tryLock(3, TimeUnit.SECONDS);try {product = getProductFromCache(productCacheKey);if (product != null) {return product;}//RLock updateProductLock = redisson.getLock(LOCK_PRODUCT_UPDATE_PREFIX + productId);RReadWriteLock readWriteLock = redisson.getReadWriteLock(LOCK_PRODUCT_UPDATE_PREFIX + productId);RLock rLock = readWriteLock.readLock();rLock.lock();try {product = productDao.get(productId);if (product != null) {redisUtil.set(productCacheKey, JSON.toJSONString(product),genProductCacheTimeout(), TimeUnit.SECONDS);productMap.put(productCacheKey, product);} else {redisUtil.set(productCacheKey, EMPTY_CACHE, genEmptyCacheTimeout(), TimeUnit.SECONDS);}} finally {rLock.unlock();}} finally {hotCacheLock.unlock();}return product;}
private Product getProductFromCache(String productCacheKey) {Product product = productMap.get(productCacheKey);if (product != null) {return product;}String productStr = redisUtil.get(productCacheKey);if (!StringUtils.isEmpty(productStr)) {if (EMPTY_CACHE.equals(productStr)) {redisUtil.expire(productCacheKey, genEmptyCacheTimeout(), TimeUnit.SECONDS);return new Product();}product = JSON.parseObject(productStr, Product.class);redisUtil.expire(productCacheKey, genProductCacheTimeout(), TimeUnit.SECONDS); //读延期}return product;}代码
@Service
public class ProductService {@Autowiredprivate ProductDao productDao;@Autowiredprivate RedisUtil redisUtil;@Autowiredprivate Redisson redisson;public static final Integer PRODUCT_CACHE_TIMEOUT = 60 * 60 * 24;public static final String EMPTY_CACHE = "{}";public static final String LOCK_PRODUCT_HOT_CACHE_PREFIX = "lock:product:hot_cache:";public static final String LOCK_PRODUCT_UPDATE_PREFIX = "lock:product:update:";public static Map<String, Product> productMap = new ConcurrentHashMap<>();@Transactionalpublic Product create(Product product) {Product productResult = productDao.create(product);redisUtil.set(RedisKeyPrefixConst.PRODUCT_CACHE + productResult.getId(), JSON.toJSONString(productResult),genProductCacheTimeout(), TimeUnit.SECONDS);return productResult;}@Transactionalpublic Product update(Product product) {Product productResult = null;//RLock updateProductLock = redisson.getLock(LOCK_PRODUCT_UPDATE_PREFIX + product.getId());RReadWriteLock readWriteLock = redisson.getReadWriteLock(LOCK_PRODUCT_UPDATE_PREFIX + product.getId());RLock writeLock = readWriteLock.writeLock();writeLock.lock();try {productResult = productDao.update(product);redisUtil.set(RedisKeyPrefixConst.PRODUCT_CACHE + productResult.getId(), JSON.toJSONString(productResult),genProductCacheTimeout(), TimeUnit.SECONDS);productMap.put(RedisKeyPrefixConst.PRODUCT_CACHE + productResult.getId(), product);} finally {writeLock.unlock();}return productResult;}public Product get(Long productId) throws InterruptedException {Product product = null;String productCacheKey = RedisKeyPrefixConst.PRODUCT_CACHE + productId;product = getProductFromCache(productCacheKey);if (product != null) {return product;}//DCLRLock hotCacheLock = redisson.getLock(LOCK_PRODUCT_HOT_CACHE_PREFIX + productId);hotCacheLock.lock();//boolean result = hotCacheLock.tryLock(3, TimeUnit.SECONDS);try {product = getProductFromCache(productCacheKey);if (product != null) {return product;}//RLock updateProductLock = redisson.getLock(LOCK_PRODUCT_UPDATE_PREFIX + productId);RReadWriteLock readWriteLock = redisson.getReadWriteLock(LOCK_PRODUCT_UPDATE_PREFIX + productId);RLock rLock = readWriteLock.readLock();rLock.lock();try {product = productDao.get(productId);if (product != null) {redisUtil.set(productCacheKey, JSON.toJSONString(product),genProductCacheTimeout(), TimeUnit.SECONDS);productMap.put(productCacheKey, product);} else {redisUtil.set(productCacheKey, EMPTY_CACHE, genEmptyCacheTimeout(), TimeUnit.SECONDS);}} finally {rLock.unlock();}} finally {hotCacheLock.unlock();}return product;}private Integer genProductCacheTimeout() {return PRODUCT_CACHE_TIMEOUT + new Random().nextInt(5) * 60 * 60;}private Integer genEmptyCacheTimeout() {return 60 + new Random().nextInt(30);}private Product getProductFromCache(String productCacheKey) {Product product = productMap.get(productCacheKey);if (product != null) {return product;}String productStr = redisUtil.get(productCacheKey);if (!StringUtils.isEmpty(productStr)) {if (EMPTY_CACHE.equals(productStr)) {redisUtil.expire(productCacheKey, genEmptyCacheTimeout(), TimeUnit.SECONDS);return new Product();}product = JSON.parseObject(productStr, Product.class);redisUtil.expire(productCacheKey, genProductCacheTimeout(), TimeUnit.SECONDS); //读延期}return product;}}
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