[
https://issues.apache.org/jira/browse/HADOOP-8091?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Steve Loughran resolved HADOOP-8091.
------------------------------------
Resolution: Duplicate
> Add a topology mapper that reads hostname to rack mappings from a Java
> properties file
> --------------------------------------------------------------------------------------
>
> Key: HADOOP-8091
> URL: https://issues.apache.org/jira/browse/HADOOP-8091
> Project: Hadoop Common
> Issue Type: New Feature
> Components: util
> Affects Versions: 0.24.0
> Reporter: Steve Loughran
> Priority: Minor
>
> Getting mapping scripts right is surprisingly hard -and if its wrong in
> production bad things happen. It would be good to have something simpler for
> beginners -and one that is trivial to generate by a machine based on
> infrastructure data.
> I propose adding an alternative mapper, one driven by a java property file
> # the specific topology mapper must be identified for loading
> # it uses another key to identify the property file to load. This is checked
> for on startup -if missing, fail.
> # one property, perhaps "default-rack" identifies the default rack mapping
> for any host not in the list
> # every other entry lists a hostname to rack mapping
> # hostname mapping is done on the first entry in the FQDN, to be less
> brittle to domain resolution.
> Example
> {code}
> default-rack=/rack1
> host1=/rack1
> host2=/rack1
> host3=/rack2
> host4=/rack2
> {code}
> Implementation
> * add a new mapper that builds a concurrent hash map
> * read in every entry in the specified property file, add it to the map
> * when queried, extract the hostname (i.e. everything before any ".")
> * match that in the hash table, return if found
> * if not found: return the default rack
> Feature creep would be to poll this file for changes at a (specified)
> frequency, and pick up the changes when they occur. This would require
> removing the caching topology mapper that wraps all others in the NN and RM.
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators:
https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira
