Referencing Objects in a JDG cache

Issue

• Is it possible to have a reference to a cached object outside the cache and have it synchronized with the cluster?
• Is there a way to reference the last version of an object in a DataGrid cache?
  Lets assume that on node1 the object for "A" is retrieved from the cache and stored as referece, is it possible to see updates which are made on node2?
• Is there a problem if I modify Objects which I read from a JDG cache?
• Why should I prefer imutable objects for caching?
• A cache configured with a persistence write-behind will fail to start if preload=true with Exceptions

Caused by: org.infinispan.persistence.spi.PersistenceException: java.io.StreamCorruptedException: Unexpected byte found when reading an object: 0
used by: org.infinispan.commons.CacheException: Unable to invoke method public void org.infinispan.persistence.manager.PreloadManager.start() on object of type PreloadManager
    at org.infinispan.commons.util.ReflectionUtil.invokeMethod(ReflectionUtil.java:193) [infinispan-commons-9.4.18.Final-redhat-00001.jar:9.4.18.Final-redhat-00001]
    at org.infinispan.factories.impl.BasicComponentRegistryImpl.startWrapper(BasicComponentRegistryImpl.java:520) [infinispan-core-9.4.18.Final-redhat-00001.jar:9.4.18.Final-redhat-00001]
    at org.infinispan.factories.impl.BasicComponentRegistryImpl$ComponentWrapper.running(BasicComponentRegistryImpl.java:711) [infinispan-core-9.4.18.Final-redhat-00001.jar:9.4.18.Final-redhat-00001]
    at org.infinispan.factories.impl.BasicComponentRegistryImpl.startDependencies(BasicComponentRegistryImpl.java:552) [infinispan-core-9.4.18.Final-redhat-00001.jar:9.4.18.Final-redhat-00001]
       .....

• ConcurrentModificationExceptions messages are logged like followed for caches configured with write-behind

DEBUG [org.infinispan.persistence.async.AsyncCacheWriter] (AsyncStoreProcessor--p30-t10) Failed to process async modifications: org.infinispan.persistence.spi.PersistenceException: org.infinispan.persistence.spi.PersistenceException: java.util.ConcurrentModificationException
    at org.infinispan.persistence.file.SingleFileStore.write(SingleFileStore.java:373) [infinispan-core-9.4.18.Final-redhat-00001.jar:9.4.18.Final-redhat-00001]
    at java.lang.Iterable.forEach(Iterable.java:75) [rt.jar:1.8.0_242]
    at org.infinispan.persistence.spi.CacheWriter.writeBatch(CacheWriter.java:47) [infinispan-core-9.4.18.Final-redhat-00001.jar:9.4.18.Final-redhat-00001]
    at org.infinispan.persistence.async.AsyncCacheWriter.applyModificationsSync(AsyncCacheWriter.java:226) [infinispan-core-9.4.18.Final-redhat-00001.jar:9.4.18.Final-redhat-00001]
    ...
Caused by: org.infinispan.persistence.spi.PersistenceException: java.util.ConcurrentModificationException
    at org.infinispan.marshall.core.MarshalledEntryImpl.marshall(MarshalledEntryImpl.java:132) [infinispan-core-9.4.18.Final-redhat-00001.jar:9.4.18.Final-redhat-00001]
    at org.infinispan.marshall.core.MarshalledEntryImpl.getValueBytes(MarshalledEntryImpl.java:113) [infinispan-core-9.4.18.Final-redhat-00001.jar:9.4.18.Final-redhat-00001]
    at org.infinispan.persistence.file.SingleFileStore.write(SingleFileStore.java:330) [infinispan-core-9.4.18.Final-redhat-00001.jar:9.4.18.Final-redhat-00001]
    ... 8 more
Caused by: java.util.ConcurrentModificationException
    at java.util.HashMap$HashIterator.nextNode(HashMap.java:1445) [rt.jar:1.8.0_242]
    at java.util.HashMap$KeyIterator.next(HashMap.java:1469) [rt.jar:1.8.0_242]

• State transfer will fail if a new instance is started with one of the following messages shown in both instances.

ERROR [org.infinispan.remoting.transport.jgroups.JGroupsTransport] (jgroups-4463,jboss90432-63171) ISPN000475: Error processing response for request 10782325 from jboss90434-61244

ERROR [org.infinispan.remoting.transport.jgroups.JGroupsTransport] (jgroups-18,jboss90434-61244) ISPN000474: Error processing request 10782325@jboss90432-63171