|| at Jul 21, 2012 at 3:55 am
Any HDFS client can request a list of block locations for a given file
path (node-level detail of where blocks are placed for a file), via
the FileSystem#getFileBlockLocations API:http://hadoop.apache.org/common/docs/current/api/org/apache/hadoop/fs/FileSystem.html#getFileBlockLocations(org.apache.hadoop.fs.FileStatus,%20long,%20long)
MR too gets this info via the user's InputFormat#getSplits method, and
schedules with these locations.
On Sat, Jul 21, 2012 at 2:06 AM, Kyungyong Lee wrote:
I want to get datanode information (related to block placement) that is kept
at a namenode from a jobtracker. As far as I understand, the jobtracker uses
the locality-of-data for job scheduling, so I believe the jobtracker is
keeping the information somewhere in the source code. However, I could not
find the location. Can anyone give me a starting point (source code) where
the jobtracker has access to block placement information? Thanks.