[hibernate-dev] Pooled Optimiser Improvements

[Scott Marlow]

Should this be a specialized pooled optimizer that is only used in 
environments that do not suffer from leaving the ThreadLocal around 
after the application is undeployed?  In other words, the expectation is 
that classloader leaks with this pooled optimizer are expected (e.g. 
user must restart the jvm to really undeploy the application completely).

I am thinking that there are at least three typical situations:

1.  Applications are deployed in Java standalone edition.  Generally, 
when the app undeploys the jvm is shutting down.

2. Applications are deployed as part of some container (e.g. an EE 
server) and the Hibernate jars are on the global classloader path (or 
something like that).  On each shared container thread, there would be 
one Optimizer for all deployed applications.  I wonder if instead, we 
would want one Optimizer instance per Hibernate SessionFactory 
associated with the many container threads?

3. Applications are deployed as part of some container (e.g. an EE 
server) and the Hibernate jars are deployed with the application. The 
ThreadLocals are associated with threads that are shared by different 
deployed applications. The application classloader contains the 
Hibernate classes. Each deployed application has its own Optimizer 
threadlocal. On each shared container thread, there would be one 
Optimizer per application (since each application has its Optimizer TL). 
  Like (2), there would be sharing of the same Optimizer with the many 
application session factories.  Should we instead have an optimizer per 
session factory?

Scott

On 12/10/2015 11:31 PM, Stuart Douglas wrote:
> Hello,
>
> I have been working on a change to the pooled optimizer that we have been seeing good performance results with. Basically it hands out blocks of ID's to a thread local, rather than having every thread contend on the lock every time an ID is required.
>
> https://github.com/hibernate/hibernate-orm/compare/master...stuartwdouglas:pooled-optimiser-hack
>
> What would I need to do to get a change like this in? In particular:
>
> - Does it need to be a new type of optimizer, or is modifying the existing one like I have done OK?
> - How should it be configured?
>
> I am happy to do up a PR for this, but I am just not really sure what would be required to get it to a point where it would be acceptable for inclusion.
>
> Stuart
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