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https://issues.apache.org/jira/browse/HADOOP-1296?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12492742
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dhruba borthakur commented on HADOOP-1296:
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In the current incantation, getHosts() returns the name of the host on which
the block resides. I would like to request that getPorts() be added to this
API. This is needed to write *deterministic* test case (e.g. TestDecommission)
using DFSMiniCluster where we have multiple datanodes on the same host.
> Improve interface to FileSystem.getFileCacheHints
> -------------------------------------------------
>
> Key: HADOOP-1296
> URL: https://issues.apache.org/jira/browse/HADOOP-1296
> Project: Hadoop
> Issue Type: Improvement
> Components: fs
> Reporter: Owen O'Malley
> Assigned To: dhruba borthakur
>
> The FileSystem interface provides a very limited interface for finding the
> location of the data. The current method looks like:
> String[][] getFileCacheHints(Path file, long start, long len) throws
> IOException
> which returns a list of "block info" where the block info consists of a list
> host names. Because the hints don't include the information about where the
> block boundaries are, map/reduce is required to call the name node for each
> split. I'd propose that we fix the naming a bit and make it:
> public class BlockInfo extends Writable {
> public long getStart();
> public String[] getHosts();
> }
> BlockInfo[] getFileHints(Path file, long start, long len) throws IOException;
> So that map/reduce can query about the entire file and get the locations in a
> single call.
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