Make EC2 cluster nodes more independent of each other
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Key: HADOOP-2410
URL: https://issues.apache.org/jira/browse/HADOOP-2410
Project: Hadoop
Issue Type: Improvement
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
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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