Cache is not alive (STATUS_SHUTD

错误报警

[2019-01-07 15:30:25.237] [SIGTERM handler] [INFO] [out-flow-logger] - stopping, Step [5/5] Begin to do shutdownActions,for example spring context
Exception in thread "SaveThread-pool-1-thread-2" java.lang.IllegalStateException: The callinfo Cache is not alive (STATUS_SHUTDOWN)
    at net.sf.ehcache.Cache$CacheStatus.checkAlive(Cache.java:4075)
    at net.sf.ehcache.Cache.checkStatus(Cache.java:2766)
    at net.sf.ehcache.Cache.get(Cache.java:1727)
    at net.sf.ehcache.Cache.get(Cache.java:1707)
    at com.vip.ads.service.common.queue.DiskQueue.pop(DiskQueue.java:59)
    at com.vip.ads.service.common.queue.SaveThread.run(SaveThread.java:43)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
Exception in thread "SaveThread-pool-1-thread-3" Exception in thread "SaveThread-pool-1-thread-1" java.lang.IllegalStateException: The callinfo Cache is not alive (STATUS_SHUTDOWN)
    at net.sf.ehcache.Cache$CacheStatus.checkAlive(Cache.java:4075)
    at net.sf.ehcache.Cache.checkStatus(Cache.java:2766)
    at net.sf.ehcache.Cache.get(Cache.java:1727)
    at net.sf.ehcache.Cache.get(Cache.java:1707)
    at com.vip.ads.service.common.queue.DiskQueue.pop(DiskQueue.java:59)
    at com.vip.ads.service.common.queue.SaveThread.run(SaveThread.java:43)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
java.lang.IllegalStateException: The callinfo Cache is not alive (STATUS_SHUTDOWN)
    at net.sf.ehcache.Cache$CacheStatus.checkAlive(Cache.java:4075)
    at net.sf.ehcache.Cache.checkStatus(Cache.java:2766)
    at net.sf.ehcache.Cache.get(Cache.java:1727)
    at net.sf.ehcache.Cache.get(Cache.java:1707)
    at com.vip.ads.service.common.queue.DiskQueue.pop(DiskQueue.java:59)
    at com.vip.ads.service.common.queue.SaveThread.run(SaveThread.java:43)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)

从代码可以知道出错的地方在DiskQueue.pop。原因是Thread还没有执行完，cache就已经关闭了。

代码review

@Component
public class DiskQueue implements InitializingBean {

    private static Ehcache cache;

    @Resource(name = "ehcacheManager")
    private CacheManager cacheManager;

    private static AtomicLong index = new AtomicLong(0);

    private static AtomicLong dealIndex = new AtomicLong(0);

    private static long getNowIndex(){
        return index.incrementAndGet();
    }

    private static long getNowDealIndex() {
        return dealIndex.incrementAndGet();
    }

    private static void resetIndex() {
        index.set(0);
    }

    private static void resetDealIndex() {
        dealIndex.set(0);
    }

    public void push(List<CallInfo> callList) {
        if(null != cache){
            return;
        }
        Element element = new Element(getNowIndex(),callList);
        cache.put(element);
    }

    public static List<CallInfo> pop() {
        long nowDealIndex = dealIndex.get();  // 这里出了问题，index并没有增加
        long nowIndex = index.get();
        if(nowDealIndex > nowIndex){
            resetIndex();
            resetDealIndex();
            return null;
        }

        if(cache == null){
            return null;
        }

        Element element = cache.get(nowDealIndex);   // 出错，cache已经被关闭
        if(element==null){
            return null;
        }

        Object obj = element.getObjectValue();
        if(obj == null){
            return null;
        }
        List<CallInfo> callInfos = (List<CallInfo>)obj;
        cache.remove(nowDealIndex);
        return callInfos;
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        EhCacheCache tmpCache = (EhCacheCache) cacheManager.getCache("callinfo");
        cache = tmpCache.getNativeCache();
    }
}

问题点在于long nowDealIndex = dealIndex.get();这行代码，当队列执行pop操作的时候，拿到的缓存下标一直都是初始化的下标0。第一次pop，是能够成功获取缓存对象的，获取完成就会把下标为0的Element从缓存中删除。那么之后的每次获取拿到的都是null。

看了下get()方法的源码：

public final Element get(Serializable key) throws IllegalStateException, CacheException {
        return this.get((Object)key);
    }

public final Element get(Object key) throws IllegalStateException, CacheException {
        this.getObserver.begin();
        this.checkStatus();
        if (this.disabled) {
            this.getObserver.end(GetOutcome.MISS_NOT_FOUND);
            return null;
        } else {
            Element element = this.compoundStore.get(key);
            if (element == null) {
                this.getObserver.end(GetOutcome.MISS_NOT_FOUND);
                return null;
            } else if (this.isExpired(element)) {
                this.tryRemoveImmediately(key, true);
                this.getObserver.end(GetOutcome.MISS_EXPIRED);
                return null;
            } else {
                if (!this.skipUpdateAccessStatistics(element)) {
                    element.updateAccessStatistics();
                }

                this.getObserver.end(GetOutcome.HIT);
                return element;
            }
        }
    }

public void end(T result) {
        ((LongAdder)this.counts.get(result)).increment();
        if (!this.derivedStatistics.isEmpty()) {
            long time = Time.time();
            Iterator i$ = this.derivedStatistics.iterator();

            while(i$.hasNext()) {
                ChainedOperationObserver<? super T> observer = (ChainedOperationObserver)i$.next();
                observer.end(time, result);
            }
        }
}

从源码看到，如果获取到的Element对象为空，就不仅仅是返回空对象这个简单的操作，还有this.getObserver.end(GetOutcome.MISS_NOT_FOUND)。初步推断Ehcache中有自己的关闭机制，达到n次get()返回为空之后就会自动关闭cache。

有明确知道这个原因的小伙伴希望私信或评论一下我哈~共同学习进步。