[hibernate-dev] HHH-13916 / WFLY-13259

I've been looking into how to fix this issue: https://hibernate.atlassian.net/browse/HHH-13916 https://issues.redhat.com/browse/WFLY-13259 The crux of the matter is when Hibernate calls CacheHelper.fromSharedCache( session, cacheKey, cachAccess ), and the entity is not found in the cache, Infinispan stores a PendingPut containing a SharedSessionContractImplementor instance. IIUC, as an optimization, Infinispan assumes that the entity not found in the cache will ultimately be added to the cache after it is loaded from the database. If that doesn't happen, the PendingPut will expire and will eventually be removed. Until it expires, the SharedSessionContractImplementor instance cannot be garbage-collected. This is particularly a problem if the cache is not disabled while a large amount of cacheable data is being imported. This is the particular use case described by WFLY-13259. There is a reproducer attached that throws OutOfMemoryError. The obvious workaround is to set org.hibernate.CacheMode.IGNORE (or possibly CacheMode.PUT?) while importing data. I discussed this briefly with Sanne, and we agree that an improvement would be to not store a SharedSessionContractImplementor in a PendingPut at all. There is already a way to get a UUID for the session by calling SharedSessionContractImplementor#getSessionIdentifier(). Unfortunately, the implementation in AbstractSharedSessionContract indicates that frequent "UUID generations will cause a significant amount of contention". Sanne has suggested returning a "token" that is just a new Object. I've created a branch <https://github.com/gbadner/hibernate-core/tree/HHH-13916_token> [1] that does this. Infinispan would need to be updated so that PendingPut#owner is set to SharedSessionContractImplementor#getSessionToken() (instead of the SharedSessionContractImplementor object). Looking at the Infinispan code, I see that code that would be affected is in org.infinispan.hibernate.cache.commons.access.PutFromLoadValidator, which is used by infinispan-hibernate-cache-v51. IIUC, in order to fix this any time soon for WildFly or EAP 7.x, [1] would have to be backported to both Hibernate ORM 5.1 and 5.3 branches, and the Hibernate versions would have to be updated in Infinispan before Infinispan could be updated to use SharedSessionContractImplementor#getSessionToken(). Galder/Radim, are there any plans for dropping infinispan-hibernate-cache-v51? Are there other places where the SharedSessionContractImplementor is stored in the cache? Aside from infinispan-hibernate-cache-v51, do you see anything about [1] that would cause problems? If not, when do you think we could coordinate this change? Do we need to wait for Hibernate ORM 6.0? This is considered an improvement, so it's not urgent. It would be nice to fix this though. Galder/Radim, please provide your input so we figure out when it can be fixed. Thanks, Gail [1] https://github.com/gbadner/hibernate-core/tree/HHH-13916_token [2]