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https://issues.apache.org/jira/browse/HADOOP-2410?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12588025#action_12588025
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Chris K Wensel commented on HADOOP-2410:
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Good idea re configurable memory for the trackers and datanode services, though 
I find the defaults fine (so far). But I tend to pass my child vm option in per 
job since they vary. Still a good idea to provide the option.

Note that:

  hadoop-ec2 proxy <cluster-name> 

starts a local SOCKS tunnel. Used with FoxyProxy FF plugin, you can browse your 
cluster.

> Make EC2 cluster nodes more independent of each other
> -----------------------------------------------------
>
>                 Key: HADOOP-2410
>                 URL: https://issues.apache.org/jira/browse/HADOOP-2410
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: contrib/ec2
>    Affects Versions: 0.16.1
>            Reporter: Tom White
>            Assignee: Chris K Wensel
>             Fix For: 0.17.0
>
>         Attachments: concurrent-clusters-2.patch, 
> concurrent-clusters-3.patch, concurrent-clusters.patch, ec2.tgz
>
>
> The cluster start up scripts currently wait for each node to start up before 
> appointing a master (to run the namenode and jobtracker on), and copying 
> private keys to all the nodes, and writing the private IP address of the 
> master to the hadoop-site.xml file (which is then copied to the slaves via 
> rsync). Only once this is all done is hadoop started on the cluster (from the 
> master). This can fail if any of the nodes fails to come up, which can happen 
> as EC2 doesn't guarantee that you get a cluster of the size you ask for (I've 
> seen this happen).
> The process would be more robust if each node was told the address of the 
> master as user metadata and then started its own daemons. This is complicated 
> by the fact that the public DNS alias of the master resolves to a public IP 
> address so cannot be used by EC2 nodes (see 
> http://docs.amazonwebservices.com/AWSEC2/2007-08-29/DeveloperGuide/instance-addressing.html).
>  Instead we need to use a trick 
> (http://developer.amazonwebservices.com/connect/message.jspa?messageID=71126#71126)
>  to find the private IP, and what's more we need to attempt to resolve the 
> private IP in a loop until it is available since the DNS will only be set up 
> after the master has started.
> This change will also mean the private key doesn't need to be copied to each 
> node, which can be slow and has dubious security. Configuration can be 
> handled using the mechanism described in HADOOP-2409.

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