背景介绍
我们使用SpringCache框架 Redis来实现项目中的缓存实现，它能实现自动对数据缓存，也可以自动清理过期的缓存。大多数情况下，它都运行非常好。
这是因为我们需要缓存的数据，通常都是可序列化的，但是我们迟早会遇到不可序列化的对象。那么我们只能选择SpringCache中的ConcurrentMapCache才能缓存这些不可序列化的对象，但是ConcurrentMapCache呢又不提供自动清理缓存的功能。
于是我开始自己设计一个本地的、高效的、能自动清理缓存扩展，同样它能支持SpringCache。
为了高效的清理缓存，我采用分桶策略，这一设计思想来源于ZooKeeper的Session管理。分桶策略也是本文的精彩内容。
SpringCache的使用
SpringCache Redis自动清理缓存
代码语言：javascript复制@EnableCaching
@Configuration
public class RedisCacheAutoConfiguration {
@Autowired
private RedisConnectionFactory redisConnectionFactory;
@Primary
@Bean("redisCacheManager")
public CacheManager cacheManager() {
RedisCacheManager cacheManager = new RedisCacheManager(
RedisCacheWriter.nonLockingRedisCacheWriter(redisConnectionFactory),
getTtlRedisCacheConfiguration(CacheNameEnum.DEFAULT),
getCustomizeTtlRedisCacheConfigurationMap());
return cacheManager;
}
private Map<String, RedisCacheConfiguration> getCustomizeTtlRedisCacheConfigurationMap() {
Map<String, RedisCacheConfiguration> redisCacheConfigurationMap = new HashMap<>();
for (CacheNameEnum cacheNameEnum : CacheNameEnum.values()) {
redisCacheConfigurationMap.put(cacheNameEnum.name(), getTtlRedisCacheConfiguration(cacheNameEnum));
}
return redisCacheConfigurationMap;
}
private RedisCacheConfiguration getTtlRedisCacheConfiguration(CacheNameEnum cacheNameEnum) {
GenericFastJsonRedisSerializer fastJsonRedisSerializer = new GenericFastJsonRedisSerializer();
StringRedisSerializer stringRedisSerializer = new StringRedisSerializer();
RedisSerializationContext.SerializationPair<Object> objectSerializationPair = RedisSerializationContext.SerializationPair.fromSerializer(fastJsonRedisSerializer);
RedisSerializationContext.SerializationPair<String> stringSerializationPair = RedisSerializationContext.SerializationPair.fromSerializer(stringRedisSerializer);
RedisCacheConfiguration redisCacheConfiguration = RedisCacheConfiguration.defaultCacheConfig();
redisCacheConfiguration = redisCacheConfiguration.serializeKeysWith(stringSerializationPair)
.serializeValuesWith(objectSerializationPair)
.entryTtl(Duration.ofSeconds(cacheNameEnum.getTtl()));
return redisCacheConfiguration;
}
enum CacheNameEnum {
DEFAULT(60);
private int ttl;
CacheNameEnum(int ttl) {
this.ttl = ttl;
}
public int getTtl() {
return ttl;
}
}
}那么使用的时候，就只需要增加注解就行了
代码语言：javascript复制 @Cacheable(cacheManager = "redisCacheManager", cacheNames = "DEFAULT", key = "'nft:transafer:' #mnemonic")
public Transafer recover(String mnemonic) {
return new Transafer(mnemonic, wenchangChainPropertity);
}SpringCache Map本地缓存
代码语言：javascript复制// 记得加上@EnableCaching，开启缓存
@Bean("localCacheManager")
public CacheManager localCacheManager() {
ConcurrentMapCache publicKeyCache = new ConcurrentMapCache("localCache");
Set<Cache> caches = new HashSet<>();
caches.add(publicKeyCache);
SimpleCacheManager cacheManager = new SimpleCacheManager();
cacheManager.setCaches(caches);
return cacheManager;
}那么使用的时候，就只需要增加注解就行了
代码语言：javascript复制 @Cacheable(cacheManager = "localCacheManager", cacheNames = "localCache", key = "'nft:transafer:' #mnemonic")
public Transafer recover(String mnemonic) {
return new Transafer(mnemonic, wenchangChainPropertity);
}SpringCache Map自动清理本地缓存
为了实现自动清理缓存，我继承了ConcurrentMapCache，采用分桶策略，定时清理。
- • expirationInterval，桶的估计范围，如果为1分钟，那么1分钟内创建的缓存都存在一个桶，例如16:11:20和16:11:01，都会存放在16:12:00这个桶中。
- • roundToNextInterval，用于根据当前时间计算，下一个桶的时间。
- • executorService，用于清理缓存，仅仅在创建桶时，调用其该线程，并不会实时运行，占用CPU资源。
public class LocalExpiryCache extends ConcurrentMapCache {
private static Logger log = LoggerFactory.getLogger(LocalExpiryCache.class);
/**
* 桶的范围
*/
public final long expirationInterval;
private static ScheduledExecutorService executorService = new ScheduledThreadPoolExecutor(5, NftThreadFactory.create("cache-cleara", true));
private static final Map<Long, Set<Object>> expiryMap = new ConcurrentHashMap<>();
public LocalExpiryCache(String name, long expirationInterval) {
super(name);
this.expirationInterval = expirationInterval;
}
@Override
public void put(Object key, Object value) {
log.info("=======put=======");
super.put(key, value);
long now = System.currentTimeMillis();
long expires = roundToNextInterval(now);
log.info("expires: " DateUtil.formatDate(new Date(expires), DateUtil.FORMAT_DATETIME_NORMAL));
if (!expiryMap.containsKey(expires)) {
synchronized (this) {
if (!expiryMap.containsKey(expires)) {
expiryMap.put(expires, new ConcurrentHashSet<>());
executorService.schedule((Runnable) this::expiry, expires - now 100
, TimeUnit.MILLISECONDS);
}
}
}
Set<Object> objects = expiryMap.get(expires);
objects.add(key);
}
@Override
public ValueWrapper putIfAbsent(Object key, Object value) {
log.info("=======putIfAbsent=======");
return super.putIfAbsent(key, value);
}
private long roundToNextInterval(long time) {
return (time / expirationInterval 1) * expirationInterval;
}
public Set expiry() {
log.info("-------------------------------------");
long now = System.currentTimeMillis();
Set<Long> ttls = expiryMap.keySet();
if (CollectionUtils.isEmpty(ttls)) {
return Collections.emptySet();
}
Iterator<Long> iterator = ttls.iterator();
Set result = new HashSet();
while (iterator.hasNext()) {
Long expirationTime = iterator.next();
if (now < expirationTime) {
break;
}
result.addAll(expiryMap.get(expirationTime));
iterator.remove();
}
for (Object key : result) {
super.evict(key);
}
log.info("evict size: " result.size());
return result;
}
public static void main(String[] args) throws Exception {
LocalExpiryCache localCache = new LocalExpiryCache("", 1 * 60 * 1000);
localCache.put("1", "");
localCache.put("2", "");
log.info(localCache.getNativeCache().size() "");
Thread.sleep(1 * 60 * 1000);
log.info(localCache.getNativeCache().size() "");
localCache.put("2", "");
Thread.sleep(1 * 60 * 1000);
log.info(localCache.getNativeCache().size() "");
System.in.read();
}
}使用时，用LocalExpiryCache替换掉ConcurrentMapCache即可
代码语言：javascript复制@Bean("localCacheManager")
public CacheManager localCacheManager() {
LocalExpiryCache publicKeyCache = new LocalExpiryCache("localCache", 1 * 60 * 1000);
Set<Cache> caches = new HashSet<>();
caches.add(publicKeyCache);
SimpleCacheManager cacheManager = new SimpleCacheManager();
cacheManager.setCaches(caches);
return cacheManager;
}
