[hibernate-dev] JPA2 locking followup...
smarlow at redhat.com
Fri Oct 30 15:42:21 EDT 2009
On 10/30/2009 02:08 PM, Steve Ebersole wrote:
> As I said on IRC, my belief is that we should expand this set of lock
> modes specifically to include NO_WAIT variants. Its really just a
> question of for which modes it makes sense. The spec says
> "javax.persistence.lock.timeout" is "defined by this specification for
> use in pessimistic locking" so obviously OPTIMISTIC and
> OPTIMISTIC_FORCE_INCREMENT are fine by themselves.
This is probably cleaner than the JPA2 overloading of timeout property
(value of zero meaning NO_WAIT).
> I don't think PESSIMISTIC_FORCE_INCREMENT needs a NO_WAIT variant, even
> if we were to support using this mode on non-versioned entities.
> I am unclear yet whether PESSIMISTIC_READ will require a NO_WAIT
If PESSIMISTIC_READ is implemented with PESSIMISTIC_WRITE support, I
would think yes.
> Conversely for "with wait" semantics we will need to add support for the
> lock acquisition timeout.
> On Fri, 2009-10-30 at 13:49 -0400, Scott Marlow wrote:
>> How should we handle the _NOWAIT variants for the three Pessimistic
>> modes? The JPA2 style is to use the "javax.persistence.lock.timeout
>> (time in milliseconds, with 0 meaning no wait).
>> Internally, we need Hibernate core to support the three pessimistic lock
>> modes (read, write, force_increment) with a JPA2 style timeout option.
>> Since, we need to support JPA2 timeout per requested lock, we might want
>> to support _NOWAIT via the same mechanism as we use for timeout.
>> On 10/30/2009 09:18 AM, Scott Marlow wrote:
>>> For JPA2 support, I propose that Hibernate LockMode support the
>>> following equivalents of JPA2 LockModeType locks:
>>> LockMode.OPTIMISTIC (READ)
>>> LockMode.OPTIMISTIC_FORCE_INCREMENT (WRITE)
>>> Hibernate already supports NONE, so that doesn't need to be added. JPA2
>>> defaults to LockModeType NONE.
>>> JPA1 READ + WRITE will be supported respectively via LockMode.OPTIMISTIC
>>> + LockMode.OPTIMISTIC_FORCE_INCREMENT.
>>> With this change, Hibernate (native (better term?)) applications would
>>> be able to request JPA2 like locks. This also means that JPA2
>>> applications running with the Hibernate Entity Manager, will see similar
>>> locking behavior as native applications.
>>> - Application developers will have a consistent set of locking options
>>> in their JPA2 based applications and native Hibernate applications.
>>> - This helps the application developer to prepare their native Hibernate
>>> application to migrate to JPA2.
>>> - This ties Hibernate core locking internals to the JPA2 specification.
>>> As JPA continues to evolve, Hibernate core should follow in lockstep.
>>> Although, that is not a hard requirement.
>>> - An alternative would be introducing low level locking primitives that
>>> could be combined to support JPA2 style locks. I can explore this path
>>> if there is strong push back to the above proposal.
>>> hibernate-dev mailing list
>>> hibernate-dev at lists.jboss.org
>> hibernate-dev mailing list
>> hibernate-dev at lists.jboss.org
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