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From "Tom White (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-2410) Make EC2 cluster nodes more independent of each other
Date Thu, 27 Mar 2008 09:53:24 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-2410?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12582578#action_12582578

Tom White commented on HADOOP-2410:

Amazon has just released a new feature, EC2 Availability Zones (http://developer.amazonwebservices.com/connect/entry.jspa?externalID=1347&categoryID=112),
which give some control over instance placement. This would be useful for adding nodes on
the fly to an existing cluster to ensure that nodes are in the same zone.

Also, it is now possible to use the public IP address of EC2 nodes from within the EC2 cluster
(contrary to the comment in the description above). However, this will incur data transfer
costs, which can be avoided by using the private IP address. See http://docs.amazonwebservices.com/AWSEC2/2008-02-01/DeveloperGuide/instance-addressing.html.

> 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
>            Reporter: Tom White
> 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
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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