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From Berin Loritsch <blorit...@apache.org>
Subject Re: [C2]: Component Pooling and recycling
Date Wed, 21 Feb 2001 13:41:34 GMT
Carsten Ziegeler wrote:
> 
> Using the latest cvs of C2, I have the following questions/remarks to the component pooling:
> 
> Questions first:
> 1. Looking up a component using the ComponentManager:
>    - Am I right that when the component is not Poolable I always get the same instance?

No.  Some are Factory components and are created fresh each time.  If it is marked ThreadSafe,
then you should get the same instance everytime.

>    - When the component is Poolable (or PoolClient) is it the response of the "looking
up component" to put it back into the pool ?

Unfortunately, that is the way it is.  This does not change even when we are using the
Pool interface like it was meant to be used (get/put).
BTW: the "looking up component" is called a Composer--it even has an interface.

> 2. Is it correct that Actions are never pooled or recycled?

Yes.  They are ThreadSafe by design, and so should be one instance for all time.

> Now the remarks:
> 
> 3. If a sitemap component is only Recyclable (without Poolable or PoolClient) it is not
recycled.

True.  Recyclable does not necessarily mean Poolable (Not sure of the reasoning, but that's
the
way the framework is set up).  The recycle() method is used to "reset" the component back
to
it's original status.

> 4. If a sitemap component is only Poolable but not PoolClient it is not put back into
the pool.

That is an unfortunate side effect of the way the current ComponentManager/Selector interface
is.
If they had a put() method to return the Component on general principle, then it would make
for
a more elegant solution.  The temporary solution is to make anything that is Poolable a PoolClient.

> I would suggest to change the behaviour of 3. and 4. that Recyclable sitemap components
are always recycled and that Poolable sitemap components are alyways returned to the pool
- regardless if they declare PoolClient or not.

They used to be simply Poolable, and not PoolClients.  The PoolClients were created as a method
of
actually returning the Components to the Pool.  Otherwise what we have is a factory method
that simply
creates more and more components all the time.  What's worse, they have a reference on them
in the pool,
so they are never garbage collected.

Any Poolable client should be made PoolClients, and any usage of a PoolClient should call
the returnToPool
method.  Also, the recycle() method is called by the ComponentPool.  In any other context,
it's really not
useful.

> If there are no objections against the changes I will do them.

The Pool code does need to be optimized, but let's standardize on all Poolable Components
should be
PoolClients--otherwise you will find that no Component can be returned to the pool without
a reference
to the pool.

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