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https://issues.apache.org/jira/browse/HDFS-778?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12780386#action_12780386
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Suresh Srinivas commented on HDFS-778:
--------------------------------------
Looks like datanodes are registering with IP address as the name in
registration instead of host name. I in suspect o.a.h.net.DNS,
{{InetAddress.getLocalHost().getCanonicalHostName()}} is returning the IP
address. Not sure if this is due to some java SecurityManager issue.
> DistributedFileSystem.getFileBlockLocations() may occasionally return numeric
> ips as hostnames.
> -----------------------------------------------------------------------------------------------
>
> Key: HDFS-778
> URL: https://issues.apache.org/jira/browse/HDFS-778
> Project: Hadoop HDFS
> Issue Type: Bug
> Reporter: Hong Tang
>
> DistributedFileSystem.getFileBlockLocations() may occasionally return numeric
> ips as hostnames. This seems to be a breach of the
> FileSystem.getFileBlockLocation() contract:
> {noformat}
> /**
> * Return an array containing hostnames, offset and size of
> * portions of the given file. For a nonexistent
> * file or regions, null will be returned.
> *
> * This call is most helpful with DFS, where it returns
> * hostnames of machines that contain the given file.
> *
> * The FileSystem will simply return an elt containing 'localhost'.
> */
> public BlockLocation[] getFileBlockLocations(FileStatus file,
> long start, long len) throws IOException
> {noformat}
> One (maybe minor) consequence of this issue is: When a job includes such
> numeric ips in in its splits' locations, JobTracker would not be able to
> assign the job's map tasks local to the file blocks.
> We should either fix the implementation or change the contract. In the latter
> case, JobTracker needs to be fixed to maintain both the hostnames and ips of
> the TaskTrackers.
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