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From "Abmar Barros (JIRA)" <j...@apache.org>
Subject [jira] Updated: (ZOOKEEPER-702) GSoC 2010: Failure Detector Model
Date Wed, 23 Jun 2010 03:58:50 GMT

     [ https://issues.apache.org/jira/browse/ZOOKEEPER-702?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Abmar Barros updated ZOOKEEPER-702:

    Attachment: ZOOKEEPER-702.patch

Agreed with what Flavio said about the second point. The application scheduling interval is,
indeed, much lower than the FD pinging interval.

Attached the implementations of all initially suggested FDs and their unit tests. Also have
included the suggestions Flavio gave concerning package naming and method scope. 

Once the Phi Accrual implementation needs to compute the Normal Distribution cdf, I have used
the math-commons API, however, it still has to be added as an Ivy dependency.

So, before experimenting, there are a few steps that need to be accomplished:

* Create a receiveAppHeartbeat() method on the interface so that we can keep using zookeeper
messages as heartbeats and analyze its impact and adapt it to each FD implementation
* Adapt server side code to use the proposed FD interface
* Add comments to pseudo codes
* Expand unit tests
* Enhance code documentation
* Add math-commons dependency to Ivy

> 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, chen-pseudo.txt, phiaccrual-pseudo.txt, 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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