[jboss-jira] [JBoss JIRA] (JGRP-1317) Compress Digest and MutableDigest

[Bela Ban (JIRA)]

    [ https://issues.jboss.org/browse/JGRP-1317?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12801816#comment-12801816 ] 

Bela Ban commented on JGRP-1317:
--------------------------------

More optimizations (in conjunction with delta views, JGRP-1354):
* Send the full view and digest to the joining member(s)
* Send only the *delta view* to the existing members, e.g. when D and E join and B leaves:
** DeltaView(+D,E -B)
* Send *no* digest to *existing members* ! 
** For -B, NAKACK will simply remove B from the xmit-table
** For +D,E, existing members will add entries to the xmit-table for D and E at seqnos [0 (0)]; we don't need to send a digest here
*** This is a great optimization, as we'd avoid sending the full view and the full digest to existing members on every JOIN

* For a state transfer we need to send the full digest
* For a merge we probably also need to send the ful view and digest
* When the coordinators change, we should probably also send the full view and digest (TBI)
                
> Compress Digest and MutableDigest
> ---------------------------------
>
>                 Key: JGRP-1317
>                 URL: https://issues.jboss.org/browse/JGRP-1317
>             Project: JGroups
>          Issue Type: Feature Request
>            Reporter: Bela Ban
>            Assignee: Bela Ban
>             Fix For: 3.4
>
>
> For large clusters, STABLE messages are quite large, and should be compressed to be sent over the wire. 
> STABLE messages are sent between members in the same view, so we could only send the ViewId + highest_delivered/highest_received seqnos.
> Everybody who receives a STABLE message grabs the View associated with the ViewId (should be the current view !) and creates a Digest based on the View and the long[] array.
> Further optimization:
> - Canonicalize digests: if everyone has (14) 20, 22, then we could write it once, give it an ID of (say) 1 and then only refer to 1 again if we encounter the same digest. Actually, as a matter of fact, most of the digests would be the same, so this optimization could have a big effect !

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