[infinispan-dev] ISPN-232 - feedback needed

[Manik Surtani]

On 25 May 2010, at 15:09, Mircea Markus wrote:

> 
> On 25 May 2010, at 16:26, Manik Surtani wrote:
> 
>> 
>> On 25 May 2010, at 14:15, Mircea Markus wrote:
>> 
>>>>> 
>>>>> But, I'd be concerned about an Infinispan thread that's needed 
>>>>> for doing a lot of critical work during a view change getting tied up 
>>>>> making a ton of notifications.
>>>> 
>>>> ^^ Yeah that's my concern.  If during a rehash we need to stop at every entry that is being moved and issue a notification, that could be costly and really slow down the rehashing process.
>>> Can't we register an *async* notification listener on ViewChanged ? 
>> 
>> You'd still have a *lot* of notifications being queued up for the notification executor since you will have 1 event *per entry* that is moved.  
> this would still happen in the same JVM as this information is needed. Just that we offer this as a service, so that users(AS being one of them) won't have to write this code.

No, if the AS does it, it will be one notification (view change) + a scan of known session ids (keys).  If we do it, it will involve 1 notification *per key* being migrated.  The cost of each notification is the construction and initialization of an event object - which includes cloning the invocation context - and placing it on an executor queue.


>> Could be thousands, tens of thousands in cases.  
>> All other notifications will be severely delayed (depending on your async notifier executor threadpool size)
> If you have an big enough thread pool (actually at least 2 threads) this should be no issue - and this should be made clear to the user.

Executor queue size?  This could start blocking?

>> 
>> 
>> --
>> Manik Surtani
>> manik at jboss.org
>> Lead, Infinispan
>> Lead, JBoss Cache
>> http://www.infinispan.org
>> http://www.jbosscache.org
>> 
>> 
>> 
>> 
>> 
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--
Manik Surtani
manik at jboss.org
Lead, Infinispan
Lead, JBoss Cache
http://www.infinispan.org
http://www.jbosscache.org