[jira] [Commented] (YARN-435) Make it easier to access cluster topology information in an AM

["Bikas Saha (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/YARN-435?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13968558#comment-13968558 ] 

Bikas Saha commented on YARN-435:
---------------------------------

Pasting the description from YARN-1722 that was closed as a dup of this.
{code}There is no way for an AM to find out the names of all the nodes in the cluster via the AMRMProtocol. An AM can only at best ask for containers at * location. The only way to get that information is via the ClientRMProtocol but that is secured by Kerberos or RMDelegationToken while the AM has an AMRMToken. This is a pretty important piece of missing functionality. There are other jiras opened about getting cluster topology etc. but they havent been addressed due to a clear definition of cluster topology perhaps. Adding a means to at least get the node information would be a good first step.{code}
This jira may have stalled in trying to figure out how to layout the topology. YARN-1722 simply asks for the list of nodes in the cluster. While defining a way to generically describe topology may be tricky - all such methods must list all the nodes in the cluster. So YARN-1722 is a much simpler problem. Whatever object we define for topology, can start with a simple list of nodes and then use the integer id of the nodes (for compaction) in the list to reference them in the other objects describing the hierarchy.

> Make it easier to access cluster topology information in an AM
> --------------------------------------------------------------
>
>                 Key: YARN-435
>                 URL: https://issues.apache.org/jira/browse/YARN-435
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>            Reporter: Hitesh Shah
>            Assignee: Omkar Vinit Joshi
>
> ClientRMProtocol exposes a getClusterNodes api that provides a report on all nodes in the cluster including their rack information. 
> However, this requires the AM to open and establish a separate connection to the RM in addition to one for the AMRMProtocol. 



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