Flavio Junqueira commented on ZOOKEEPER-702:

My understanding is that the failure detector is supposed to behave as an 
oracle that simply says dead or alive for each monitored process. The 
application on top, in this case ZooKeeper, decides what to do with that 
information. Followers and leaders will most likely use it differently.  

Your point about TCP is excellent, Ben.The way I see it the lost packets won't 
be observed for the failure detector, and they will end up translated into 
jitter due to the retransmissions, assuming they are retransmitted. Is this 
right, Abmar? 

> 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, 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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