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From "Flavio Paiva Junqueira (JIRA)" <j...@apache.org>
Subject [jira] Commented: (ZOOKEEPER-30) Hooks for atomic broadcast protocol
Date Tue, 31 Mar 2009 10:01:53 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-30?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12694042#action_12694042
] 

Flavio Paiva Junqueira commented on ZOOKEEPER-30:
-------------------------------------------------

Andrew, It would be really good for us to see a preliminary patch, just to have an idea of
how you have implemented a few things.

Although perhaps not exactly appropriate, Ben and I had a discussion offline about having
or not propose returning a zxid. Currently, only the leader proposes, since broadcast messages
are requests transformed into idempotent transactions. If we follow this model, then returning
a zxid is not a problem because the leader is the one generating a zxid and a propose call
does not block in this case.

I understand, however, that you are interested in having Zab in such a way that any process
in the ensemble can propose. If any process can propose, then it might not make sense to have
a call to propose returning a zxid. The problem of not returning a zxid is that currently
the broadcast layer and the application layer are tightly coupled and separating them creates
a potential problem for generating snapshots that we use to recover or bring a new follower
up to speed. In a little more detail, if we separate the state from the atomic broadcast and
return no zxid, then the service layer on top of zab will have no such a notion of transaction
identifiers. We currently use such identifiers to generate and guarantee a consistent state
transfer. 

 



> Hooks for atomic broadcast protocol
> -----------------------------------
>
>                 Key: ZOOKEEPER-30
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-30
>             Project: Zookeeper
>          Issue Type: New Feature
>          Components: quorum
>            Reporter: Patrick Hunt
>            Assignee: Mahadev konar
>
> Moved from SourceForge to Apache.
> http://sourceforge.net/tracker/index.php?func=detail&aid=1938788&group_id=209147&atid=1008547

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