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From "Abmar Barros (JIRA)" <j...@apache.org>
Subject [jira] Commented: (ZOOKEEPER-702) GSoC 2010: Failure Detector Model
Date Sat, 03 Jul 2010 21:03:50 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-702?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12884968#action_12884968
] 

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

While refactoring the server side of the server-client monitoring, more specifically the SessionTracking
related classes, I realized that, once the servers do not ping the clients, and they also
use app messages received from the clients as heartbeats, it is not possible to do an adaptive
monitoring of the clients. Servers do not know the time a client sends a ping and pings are
not sent frequently -- only at idle intervals.

I am finishing refactoring the server side code and I will force the use of a fixed heartbeat
strategy for now.

Comments and suggestions are welcome

> 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
>
>
> 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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