ivannov/jcache-disappointment-2.adoc

## jcache-disappointment-2.adoc

      
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              jcache-disappointment-2.adoc
            
          
Now this is not really disappointment with jCache spec per se as it was my first one.
It is more in the Hazelcast - Payara integration.


Note


the current version of Payara is working with Hazelcast 3.5.2. As far as I saw, the serialization implementation, which is the one that is heavily involved here, was changed a lot since then. So maybe all these issues were fixed.


So, as part of our workshop, we tried to showcase as well chapter 9 of the spec: Entry Processors.
We wanted when a comment was put in our comments cache, it’s description to contain also the comment author at the end.


So we implemented our simple entry processor by the spec:


public class CommentsAuthorEntryProcessor implements
        EntryProcessor<Long, Comment, Comment>, Serializable {

    @Override
    public Comment process(MutableEntry<Long, Comment> entry,
                           Object... arguments) throws EntryProcessorException {
        Comment comment = entry.getValue();
        comment.setContent(comment.getContent() + " ["
                + comment.getByUser().getUserName() + "]");
        entry.setValue(comment);
        return comment;
    }

}


Next, following the spec, we configured the entry processor in our cache implementation:


    private Cache<Long, Comment> cache;

    @PostConstruct
    public void getCommentsCache() {

        cache = cacheManager.getCache(COMMENTS_CACHE_NAME, Long.class, Comment.class);
        if (cache == null) {
            cache = cacheManager.createCache(
                    COMMENTS_CACHE_NAME,
                    new MutableConfiguration<Long, Comment>()
                            .setTypes(Long.class, Comment.class)
                            .addCacheEntryListenerConfiguration(new MutableCacheEntryListenerConfiguration<>(
                                    FactoryBuilder.factoryOf(EntryCreatedLogListener.class), null, true, true)));
        }
    }


And finally let’s try to submit a comment:


    public void submitComment(Comment newComment) {
        cache.put(newComent.getId(), newComent);
        cache.invoke(newComment, new CommentsAuthorEntryProcessor());
    }


This will fail:


java.lang.ClassNotFoundException: bg.jug.guestbook.entities.Comment
	at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	at com.hazelcast.nio.ClassLoaderUtil.tryLoadClass(ClassLoaderUtil.java:125)
	at com.hazelcast.nio.ClassLoaderUtil.loadClass(ClassLoaderUtil.java:114)
	at com.hazelcast.nio.IOUtil$1.resolveClass(IOUtil.java:113)
	at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1613)
	at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1518)
	at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1774)
	at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1351)
	at java.io.ObjectInputStream.readObject(ObjectInputStream.java:371)
	at com.hazelcast.nio.serialization.DefaultSerializers$ObjectSerializer.read(DefaultSerializers.java:201)
	at com.hazelcast.nio.serialization.StreamSerializerAdapter.read(StreamSerializerAdapter.java:41)
	at com.hazelcast.nio.serialization.SerializationServiceImpl.toObject(SerializationServiceImpl.java:276)
	at com.hazelcast.spi.impl.NodeEngineImpl.toObject(NodeEngineImpl.java:200)
	at com.hazelcast.cache.impl.AbstractCacheService.toObject(AbstractCacheService.java:270)
	at com.hazelcast.cache.impl.CacheEntryProcessorEntry.getRecordValue(CacheEntryProcessorEntry.java:132)
	at com.hazelcast.cache.impl.CacheEntryProcessorEntry.getValue(CacheEntryProcessorEntry.java:114)


The reason for this failure is the classloader that is trying to de-serialize the Comment value that I am trying to pass to the entry processor.
This one is the current thread’s context class loader.
From ClassLoaderUtil::loadClass:


        if (theClassLoader == null) {
            theClassLoader = Thread.currentThread().getContextClassLoader();
        }


Which is really different than the one of the injected CacheManager.


A workaround here was to not inject the CacheManager, but to create it manually.
Practice not really common for a Java EE application:


    private static CacheManager cacheManager;

    static {
        ClassLoader appClassLoader = JCacheCommentsManager.class.getClassLoader();
        Config config = new Config();
        config.setClassLoader(appClassLoader);
        HazelcastInstance instance = Hazelcast.newHazelcastInstance(config);
        Properties props = HazelcastCachingProvider.propertiesByInstanceName(instance.getName());
        CachingProvider cp = Caching.getCachingProvider();
        cacheManager = cp.getCacheManager(cp.getDefaultURI(), appClassLoader, props);
    }


Now calling as simple method as cache.iterator(); of a cache created by the above CacheManager hangs and after some time starts spitting these exceptions in the server log:


com.hazelcast.cache.CacheNotExistsException: Cache is already destroyed or not created yet, on Member [192.168.124.1]:5900 this
	at com.hazelcast.cache.impl.AbstractCacheRecordStore.<init>(AbstractCacheRecordStore.java:117)
	at com.hazelcast.cache.impl.CacheRecordStore.<init>(CacheRecordStore.java:61)
	at com.hazelcast.cache.impl.CacheService.createNewRecordStore(CacheService.java:76)
	at com.hazelcast.cache.impl.CachePartitionSegment$1.createNew(CachePartitionSegment.java:56)
	at com.hazelcast.cache.impl.CachePartitionSegment$1.createNew(CachePartitionSegment.java:53)
	at com.hazelcast.util.ConcurrencyUtil.getOrPutSynchronized(ConcurrencyUtil.java:40)
	at com.hazelcast.cache.impl.CachePartitionSegment.getOrCreateCache(CachePartitionSegment.java:76)
	at com.hazelcast.cache.impl.AbstractCacheService.getOrCreateCache(AbstractCacheService.java:128)
	at com.hazelcast.cache.impl.operation.AbstractCacheOperation.beforeRun(AbstractCacheOperation.java:68)
	at com.hazelcast.spi.impl.operationservice.impl.OperationRunnerImpl.run(OperationRunnerImpl.java:131)
	at com.hazelcast.spi.impl.operationservice.impl.OperationRunnerImpl.run(OperationRunnerImpl.java:315)
	at com.hazelcast.spi.impl.operationexecutor.classic.OperationThread.processPacket(OperationThread.java:142)
	at com.hazelcast.spi.impl.operationexecutor.classic.OperationThread.process(OperationThread.java:115)


This was miraculously solved by my colleage Martin Toshev by replacing all the Comment occurnces in the generic parameters of our Cache and CacheEntryProcessor implementations and instances.
Something like that:


        @PostConstruct
        public void getCommentsCache() {

            cache = cacheManager.getCache(COMMENTS_CACHE_NAME, Long.class, PayaraValueHolder.class);
            if (cache == null) {
                cache = cacheManager.createCache(
                        COMMENTS_CACHE_NAME,
                        new MutableConfiguration<Long, PayaraValueHolder>()
                                .setTypes(Long.class, PayaraValueHolder.class)
                                .addCacheEntryListenerConfiguration(new MutableCacheEntryListenerConfiguration<>(
                                        FactoryBuilder.factoryOf(EntryCreatedLogListener.class), null, true, true)));
            }
        }

        @Override
        public void submitComment(Comment newComment) {
            try {
                cache.put(newComment.getId(), new PayaraValueHolder(submittedComment));
                cache.invoke(newComment.getId(), new CommentsAuthorEntryProcessor());
            } catch (IOException e) {
                e.printStackTrace();
            }
        }


Ugly, isn’t it:


I create the CacheManager myself as if I am working outside of a Java EE container


I use a Payara-Hazelcast internal type (PayaraValueHolder) instead of my own Comment


BTW, this didn’t work either. After hanging for 12 seconds, Payara-Hazelcast threw some kind of TimeoutException.