[jboss-jira] [JBoss JIRA] Commented: (JGRP-699) NAKACK: merging of digests is incorrect

[Bela Ban (JIRA)]

    [ http://jira.jboss.com/jira/browse/JGRP-699?page=comments#action_12400722 ] 
            
Bela Ban commented on JGRP-699:
-------------------------------

Modification to last comment: we have to replace existing entries *except* the ones for the local address (local_addr.equals(sender))

> NAKACK: merging of digests is incorrect
> ---------------------------------------
>
>                 Key: JGRP-699
>                 URL: http://jira.jboss.com/jira/browse/JGRP-699
>             Project: JGroups
>          Issue Type: Bug
>    Affects Versions: 2.4, 2.4.1, 2.4.1 SP1, 2.4.1 SP2, 2.4.1 SP3, 2.4.1 SP4, 2.4.2
>            Reporter: Bela Ban
>         Assigned To: Bela Ban
>             Fix For: 2.7, 2.6.3, 2.4.3
>
>
> The merge view is:
> 2008-02-20 23:49:30,872 DEBUG [org.jgroups.protocols.pbcast.GMS]
> view=MergeView::[172.16.172.233:19382|3] [172.16.172.233:19382, 172.16.172.234:19382],
>   subgroups=[[172.16.172.233:19382|1] [172.16.172.233:19382, 172.16.172.234:19382],
>              [172.16.172.234:19382|2] [172.16.172.234:19382]],
>   digest=172.16.172.233:19382: [557 : 564(564)], 172.16.172.234:19382: [901 : 923 (923)]
> So, the digest for 234:19382 is 901-923, which means 234 could actually satisfy the retransmit request below. However, when the xmit req arrives:
> 2008-02-20 23:49:32,004 ERROR [org.jgroups.protocols.pbcast.NAKACK]
> (requester=172.16.172.233:19382, local_addr=172.16.172.234:19382)
> message 172.16.172.234:19382::919 not found in retransmission table of
> 172.16.172.233:19382:[557 : 565 (565)]
> 172.16.172.234:19382: [921 : 924 (924) (size=3, missing=0, highest stability=921)]
> , we can see that now the digest for 234:19382 is 921-924.
> In 2.4, the merge algorith for digests (NAKACK.mergeDigest()) takes the *max* of the low seqnos (MAX(901,921), in 2.5 and higher we don't touch an existing entry, so the digest for 234:19382 would still be 901-923, and we could therefore satisfy the merge request.
> SOLUTION: use the solution implemented in 2.5 and higher: don't set digests for existing entries.

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