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From "Abmar Barros (JIRA)" <j...@apache.org>
Subject [jira] Commented: (ZOOKEEPER-702) GSoC 2010: Failure Detector Model
Date Wed, 28 Jul 2010 06:07:21 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-702?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12893072#action_12893072
] 

Abmar Barros commented on ZOOKEEPER-702:
----------------------------------------

Hi Benjamin

Thanks for your feedback!
Regarding your first question, a failure detector is intended to determine when monitored
objects are to be pinged and when they are supposed to have failed. So, you can have two different
failure detectors running in two sides of the application, or you can have the failure detector
in just one side, and the other side just replies the pings messages. 
Summarizing,  a failure detector implementation is absolutely responsible for one side of
the monitoring.

Concerning your note, the failure detectors I have implemented rely on the assumption that
zk (TCP) guarantees massage delivery and in order.  To see the effects of the new failure
detection methods, we are planning to do some experiments in the next week. We can also check
if there is any effect of TCP in the adaptive fds behavior.

> 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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