On Wed, Oct 19, 2011 at 8:26 PM, Raffaele P. Guidi <[email protected]> wrote: > It's probably my fault: as a former basketball player I believe that when an > assist is missed you have to blame the one who throws the ball :) Also, > after having worked alone on DirectMemory for a long time, discussing these > matters with skilled professionals like you is a real pleasure.
Well having worked as Terracotta Field Engg, got to know a few things, and that what I discuss here. At ASF, its "we"- the community and we are all together in this :) so its no ones fault. Well during conversations and while I watched some commits at github, got a bit confused about DirectMemory objective. That's why I asked the question on other thread about it core objective. I feel we should focus on getting a release out, with know feature, and the slowly add features. Adding documentation would be vital to wide adoption. > > Thanks, > Raffaele > > On Wed, Oct 19, 2011 at 3:33 PM, Ashish <[email protected]> wrote: > >> On Wed, Oct 19, 2011 at 7:01 PM, Raffaele P. Guidi >> <[email protected]> wrote: >> > Sorry, Ashish, but I think there must be a misunderstanding: the map >> doesn't >> > contain the actual data, it is just the index to data itself, which is >> into >> > the off-heap memory. In fact it is a collection of Pointer objects, which >> > contain the offset and the lenght of the DirectBuffer that contains the >> > actual byte array. So: replicating the map (which is natively offered by >> > both hc and terracotta) means replicating the INDEX of the data, not data >> > itself. >> >> Aha, got it. I thought about the data that's why brought up the point :) >> >> > >> > Again: replication of the map(index) is one matter, distribution of the >> data >> > is a different question. I'm not proposing to use terracotta or >> hazelcast >> > for their caching features but for their *clustering* features >> >> Got it now :) >> >> > >> > On Wed, Oct 19, 2011 at 2:46 PM, Ashish <[email protected]> wrote: >> > >> >> On Wed, Oct 19, 2011 at 5:41 PM, Raffaele P. Guidi >> >> <[email protected]> wrote: >> >> > Also, on replication/distribution, we have two distinct aspects: >> >> > >> >> > >> >> > 1. *map replication* - the pointers map has to be replicated to all >> >> nodes >> >> > and each pointer have to contain also a reference to the node who >> >> "owns" the >> >> > real data >> >> > 2. *communication between nodes* - once one node knows that one >> entry >> >> is >> >> > contained in node "n" has to ask for it >> >> > >> >> > >> >> > The first point is easily covered by terracotta or hazelcast, while >> the >> >> > second one should be implemented using an RPC mechanism (Thrift or >> Avro >> >> are >> >> > both good choices). Another option is to cover also point 1 with a >> custom >> >> > replication built on top of the chosen RPC framework - of course this >> >> would >> >> > lead to another (do we really need it?) distributed map >> implementation. >> >> >> >> Disagree on this. Be it TC or Hazelcast, they shall cover both the >> points. >> >> Lets take an example of Terracotta. Its a Client-Server architecture >> >> with striping on Server side. >> >> Now if you choose TC (short for Terracotta), you got 3 options >> >> 1. Use DSO or Distributed Shared Object mode - needs instrumentation >> >> and other stuff, not recommended >> >> 2. Use Ehcache at back, and TC takes care Distributing data >> >> 3. Use Map via TC Toolkit >> >> >> >> TC will not let you know where its storing the key (which infact are >> >> stored in HA manner on Server Stripe). That's the beauty of TC. It >> >> does the faulting/flushing transparently to the user code. >> >> >> >> On Hazelcast side, it does allow to know where the key is, but the >> >> moment you use its client, it becomes transparent to you. >> >> >> >> IMHO, using any existing cache solution would complicate the user story. >> >> >> >> Distribution is a nice to have feature, and infact would lead to a >> >> wider adoption :) >> >> >> >> > >> >> > Keeping things like this is easy - of course making it >> >> efficient/performant >> >> > is a different story (i.e., should I keep a local cache of frequently >> >> > accessed items stored in other nodes? etc..). >> >> > >> >> > Ciao, >> >> > R >> >> > >> >> >> >> thanks >> >> ashish >> >> >> > >> >> >> >> -- >> thanks >> ashish >> >> Blog: http://www.ashishpaliwal.com/blog >> My Photo Galleries: http://www.pbase.com/ashishpaliwal >> > -- thanks ashish Blog: http://www.ashishpaliwal.com/blog My Photo Galleries: http://www.pbase.com/ashishpaliwal
