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From "Benjamin Reed (JIRA)" <j...@apache.org>
Subject [jira] Commented: (ZOOKEEPER-702) GSoC 2010: Failure Detector Model
Date Tue, 27 Jul 2010 05:13:16 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-702?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12892649#action_12892649
] 

Benjamin Reed commented on ZOOKEEPER-702:
-----------------------------------------

hey abmar this looks pretty cool. i think it will make the code much more clearer when we
get this in.

i'm wondering about the asymmetrical nature of the current zk fd that you've already mentioned:
one side is generating traffic and the other is responding. shouldn't that be reflected in
the interface? it is a bit confusing when parts of the interface are used on one side and
parts on the other.

on a separate note, i'm wondering if our use of TCP affects the failure detector. since TCP
automatically handles lost packets, we aren't going to lose packets like we do with UDP based
protocols.

> GSoC 2010: Failure Detector Model
> ---------------------------------
>
>                 Key: ZOOKEEPER-702
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-702
>             Project: Zookeeper
>          Issue Type: Wish
>            Reporter: Henry Robinson
>            Assignee: Abmar Barros
>         Attachments: bertier-pseudo.txt, bertier-pseudo.txt, chen-pseudo.txt, chen-pseudo.txt,
phiaccrual-pseudo.txt, phiaccrual-pseudo.txt, ZOOKEEPER-702.patch, ZOOKEEPER-702.patch, ZOOKEEPER-702.patch,
ZOOKEEPER-702.patch, ZOOKEEPER-702.patch
>
>
> Failure Detector Module
> Possible Mentor
> Henry Robinson (henry at apache dot org)
> Requirements
> Java, some distributed systems knowledge, comfort implementing distributed systems protocols
> Description
> ZooKeeper servers detects the failure of other servers and clients by counting the number
of 'ticks' for which it doesn't get a heartbeat from other machines. This is the 'timeout'
method of failure detection and works very well; however it is possible that it is too aggressive
and not easily tuned for some more unusual ZooKeeper installations (such as in a wide-area
network, or even in a mobile ad-hoc network).
> This project would abstract the notion of failure detection to a dedicated Java module,
and implement several failure detectors to compare and contrast their appropriateness for
ZooKeeper. For example, Apache Cassandra uses a phi-accrual failure detector (http://ddsg.jaist.ac.jp/pub/HDY+04.pdf)
which is much more tunable and has some very interesting properties. This is a great project
if you are interested in distributed algorithms, or want to help re-factor some of ZooKeeper's
internal code.

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