Re: [jgroups-users] Scope implementation for JGroups 4

I forgot to add: if you don't need ordered delivery, you could also 
deliver *all* messages fora given sessions in parallel. This is the same 
as using the OOB flag: you'd still have the guarantees that each message 
is delivery one and only once.

On 20/07/17 11:33, Questions/problems related to using JGroups wrote:
> 
> 
> On 20/07/17 10:19, Questions/problems related to using JGroups wrote:
>> The scope protocol has been removed from the stack in version 4.
>> Alternatively the application can now use AsynchronousInvocation with
>> RequestHandler and an application thread pool. However, with the scope
>> protocol one can take advantage of parallelism (among different 
>> scopes) with
>> sequential guarantee within a scope. How can the same be achieved via 
>> async
>> dispatching?
> 
> Messages are still guaranteed to be delivered in send-order (and 
> once-and-only-once, no duplicates).
> 
> Let's take the example of web sessions (X, Y and Z) from the manual and 
> say sender P sends 10 messages: P1-4 (session X), 5-6 (Y) and 7-10 (Z).
> 
> The messages from the same session need to be delivered in order, e.g. 
> P4 after P3, but messages P1-4 can be delivered in parallel to P5-6 and 
> P7-10.
> 
> Since all messages come from the *same sender P*, your handle() callback 
> will be invoked with P1 first, then P2 ... P10: the ordering is 
> guaranteed to be FIFO for P.
> 
> If you for example have queues for each web session and add an incoming 
> message to the corresponding queue, the messages in each queue are 
> ordered correctly, e.g. X: |P1 P2 P3 P4|, Y: |P5 P6| Z: |P7 P8 P9 P10|
> 
> If you allocate a thread for each session (or perhaps, better, a thread 
> pool), then the thread for session Z needs to dequeue messages from Z's 
> queue and deliver them to the application one-by-one; this guarantees 
> sequential delivery of messages within the same session, but parallel 
> delivery between different sessions.
> 
>> The 'Message' structure and the RequestOptions used in RPCs do
>> not include get and set scope methods.
> 
> Right, you need to add a 'scope' yourself, e.g. by using a part of the 
> payload (the message's buffer), or - better - by adding an application 
> header to each message.
> 
>> Although the scope protocol and its
>> relevant thread-pools are now removed, retaining the scope variable in
>> request options and 'Message' structure will help in achieving the same
>> using an application thread-pool.
>>
>>
>>
>> -- 
>> View this message in context: 
>> http://jgroups.1086181.n5.nabble.com/Scope-implementation-for-JGroups-4-tp11353.html 
>>
>> Sent from the JGroups - General mailing list archive at Nabble.com.
>>
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> 

-- 
Bela Ban | http://www.jgroups.org


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