[Sheepdog] [PATCH RFC 2/2] sheep: teach sheepdog to better recovery the shut-down cluster

Liu Yuan namei.unix at gmail.com
Sun Sep 18 08:40:53 CEST 2011

On 09/18/2011 11:35 AM, Liu Yuan wrote:
> From: Liu Yuan<tailai.ly at taobao.com>
> [Problem]
> Currently, sheepdog cannot recovery cluster into full functional state if any node in
> the cluster fails to join cluster after *shutdown*, because of being considered unhealthy
> (F.g. the targeted epoch content is corrupted). That is, the cluster can only get worked
> again only *if* all the nodes join the cluster successfully.
> For 14 nodes in the cluster,
>        ==========*===<--- cluster refuses to work
>                  ^
> 	        |
>            unhealthy node
> This is quit awkward. The cluster with many nodes after being shutdowned, we easily meet
> the condition that some of nodes are unhealthy that are rejected by the master during join
> stage.This patch gives sheepdog some kind of intelligence to deal with unhealthy nodes and
> process to recovery when all the nodes alive reach the agreement.
> [Design]
> This patch add a new concept into sheepdog, the *leave node*. The _leave node_ is the one
> that the master checks and finds it unhealthy (unmatched epoch content), so marks it as
> 'leave node', meaning that it is supposed to leave the cluster. The leave nodes are queued
> in the leave list, *only* exist during SD_STATUS_WAIT_FOR_FORMAT. All the leave nodes stop
> sheep itself automatically after being started.


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