[infinispan-dev] Grouping API (ISPN-312) WAS: Generated keys affected by rehash Was: https://issues.jboss.org/browse/ISPN-977

Tue May 17 13:33:50 EDT 2011

Erik,

Dan is correct that playing with hash codes is not the correct solution.  ISPN-312 is the correct approach.  Pete has been working on a first-cut of this and it should make 5.0.0.CR3.  (Understood that release candidates aren't the place to add new features, but we're adding it as a "preview", just to get feedback on the API and impl.)

Have a look at the proposed API on https://issues.jboss.org/browse/ISPN-312 and let us know if it works for you.

Cheers
Manik

On 13 May 2011, at 18:28, Erik Salter wrote:

> Hi Dan,
> 
> I don't necessarily care about which server it's on, as long as the keys for my set of caches all remain collocated.  I understand they will all end up in the same bucket, but for one hash code, that's at most 200 keys.  I must acquire a lock for a subset of them during a transaction -- so I make liberal use of the "eagerLockSingleNode" option and redirecting my calling application to execute a transaction on the local node.  Acquiring cluster-wide locks is an absolute throughput killer.
> 
> I took a look at the KeyAffinityService a while ago (when it came out) and quickly realized it would not be suitable for my purposes.  I was wondering if ISPN-977 would allow me to use it.  But you're right.  What I ultimately want is ISPN-312.
> 
> Erik
> 
> -----Original Message-----
> From: infinispan-dev-bounces at lists.jboss.org [mailto:infinispan-dev-bounces at lists.jboss.org] On Behalf Of Dan Berindei
> Sent: Friday, May 13, 2011 12:58 PM
> To: infinispan -Dev List
> Subject: Re: [infinispan-dev] Generated keys affected by rehash Was: https://issues.jboss.org/browse/ISPN-977
> 
> On Fri, May 13, 2011 at 6:38 PM, Erik Salter <esalter at bnivideo.com> wrote:
>> Yes, collocation of all keys is a large concern of my application(s).
>> 
>> Currently, I can handle keys I'm in control of (like database-generated keys), where I can play around with the hash code.   What I would love to do is collocate that data with keys I can't control (like UUIDs) so that all cache operations can be done in the same transaction on the data owner's node.
>> 
> 
> By playing around with the hash code do you mean you set the hashcode for all the keys you want on a certain server to the same value? I imagine that would degrade performance quite a bit, because we have HashMaps everywhere and your keys will always end up in the same hash bucket.
> 
> 
> ISPN-312 seems to me like a much better fit for your use case than the KeyAffinityService. Even if you added a listener to change your keys when the topology changes, that would mean on a rehash the keys could get moved to the new server and then back to the old server, whereas with ISPN-312 they will either all stay on the old node or they will all move to the new node.
> 
> Cheers
> Dan
> 
> 
>> Erik
>> 
>> -----Original Message-----
>> From: infinispan-dev-bounces at lists.jboss.org
>> [mailto:infinispan-dev-bounces at lists.jboss.org] On Behalf Of Manik
>> Surtani
>> Sent: Friday, May 13, 2011 5:25 AM
>> To: infinispan -Dev List
>> Subject: [infinispan-dev] Generated keys affected by rehash Was:
>> https://issues.jboss.org/browse/ISPN-977
>> 
>> 
>> On 11 May 2011, at 18:47, Erik Salter wrote:
>> 
>>> Wouldn't any rehash affect the locality of these generated keys, or am I missing something?
>> 
>> It would.  And hence ISPN-977, to address that.  Or is your concern keys already generated before the rehash?  The latter would certainly be a problem.  Perhaps, if this was important to the application, on detecting a change in topology, re-generate keys and move data around?  For other apps, move the "session" to the appropriate node?
>> 
>> Cheers
>> Manik
>> --
>> Manik Surtani
>> manik at jboss.org
>> twitter.com/maniksurtani
>> 
>> Lead, Infinispan
>> http://www.infinispan.org
>> 
>> 
>> 
>> 
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--
Manik Surtani
manik at jboss.org
twitter.com/maniksurtani

Lead, Infinispan
http://www.infinispan.org

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