question Re: how to Find Block Locations of a file in HDFS using JAVA API? in Archives of Support Questions (Read Only)

how to Find Block Locations of a file in HDFS using JAVA API?

YoxBox — Sat, 10 Feb 2018 16:14:56 GMT

Hello,

i want to get details "Block-Locations" of a particular file say abc.csv(500mb)(Cluster: 1NM and 3DNs).

when i -put a file it is divided into blocks of default size 64MB and spread across Hadoop Cluster.

By using Web interface "http://namenode:50070" we can find out block location across cluster.

Also by using command : hadoop fsck <file-pat> -files -blocks -locations

But what i am trying to achieve is to get these information through JAVA API or WEB- API.

Please let me know the solution if any.

Any help will be appretiated.

Re: how to Find Block Locations of a file in HDFS using JAVA API?

xyao — Wed, 14 Feb 2018 03:23:11 GMT

@Yog Prabhhu, you can get the file block information from WebHDFS REST API like

curl -i "http://<HOST>:<PORT>/webhdfs/v1/<FilePath>?op=GETFILEBLOCKLOCATIONS

The corresponding JAVA API is FileSystem.getFileBlockLocations:

public BlockLocation[] getFileBlockLocations(FileStatus file,
    long start, long len)

You will get an array of block locations like below:

[BlockLocation(offset: 0, length: BLOCK_SIZE,*   hosts: {"host1:9866", "host2:9866, host3:9866"},...,]

Re: how to Find Block Locations of a file in HDFS using JAVA API?

husseljo — Mon, 08 Aug 2022 01:03:32 GMT

Hey, do you have an idea how I can actually locate and read a specific block using BlockLocation? I want to read the block byte by byte.(I understand it might be a remote read)

Re: how to Find Block Locations of a file in HDFS using JAVA API?

VidyaSargur — Mon, 08 Aug 2022 10:17:56 GMT

@husseljo, as this is an older post, you would have a better chance of receiving a resolution by starting a new thread. This will also be an opportunity to provide details specific to your environment that could aid others in assisting you with a more accurate answer to your question. You can link this thread as a reference in your new post.