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https://issues.apache.org/jira/browse/WHIRR-167?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12973781#action_12973781
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Tom White commented on WHIRR-167:
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This covers the requirements I think. If the namenode fails to start then we
want to fail the whole cluster (in the future we may be able to do better than
this, by starting a new namenode, but this is the behaviour we want first of
all).
Note that "max percent failure" property is _per instance template_ (group of
instances). For example, imagine that we have "1 nn+jt,10 dn+tt" with 100% max
percent failure for nn+jt, and 75% for dn+tt. If the namenode fails then the
whole cluster fails, whereas up to two datanodes can fail and the cluster will
still run.
In terms of testing, Mockito (which we're already using) can be used to
simulate the relevant exceptions.
> Improve bootstrapping and configuration to be able to isolate and repair or
> evict failing nodes on EC2
> ------------------------------------------------------------------------------------------------------
>
> Key: WHIRR-167
> URL: https://issues.apache.org/jira/browse/WHIRR-167
> Project: Whirr
> Issue Type: Improvement
> Environment: Amazon EC2
> Reporter: Tibor Kiss
> Assignee: Tibor Kiss
> Attachments: whirr.log
>
>
> Actually it is very unstable the cluster startup process on Amazon EC2
> instances. How the number of nodes to be started up is increasing the startup
> process it fails more often. But sometimes even 2-3 nodes startup process
> fails. We don't know how many number of instance startup is going on at the
> same time at Amazon side when it fails or when it successfully starting up.
> The only think I see is that when I am starting around 10 nodes, the
> statistics of failing nodes are higher then with smaller number of nodes and
> is not direct proportional with the number of nodes, looks like it is
> exponentialy higher probability to fail some nodes.
> Lookint into BootstrapCluterAction.java, there is a note "// TODO: Check for
> RunNodesException and don't bail out if only a few " which indicated the
> current unreliable startup process. So we should improve it.
> We could add a "max percent failure" property (per instance template), so
> that if the number failures exceeded this value the whole cluster fails to
> launch and is shutdown. For the master node the value would be 100%, but for
> datanodes it would be more like 75%. (Tom White also mentioned in an email).
> Let's discuss if there are any other requirements to this improvement.
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