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https://issues.apache.org/jira/browse/HDFS-8246?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14535502#comment-14535502
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Colin Patrick McCabe commented on HDFS-8246:
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>From the C client, if you wanted to know what files block ID 123 was in, you
>could do {{hdfsListDirectory(fs, path="/.reserved/.blockIdToFiles/123",
>...)}}. I think one of the advantages of having a path in .reserved instead
>of a new API is everything "just works" for the C client, C++ client, webhdfs,
>etc. etc.
> Get HDFS file name based on block pool id and block id
> ------------------------------------------------------
>
> Key: HDFS-8246
> URL: https://issues.apache.org/jira/browse/HDFS-8246
> Project: Hadoop HDFS
> Issue Type: New Feature
> Components: HDFS, hdfs-client, namenode
> Reporter: feng xu
> Assignee: feng xu
> Labels: BB2015-05-TBR
> Attachments: HDFS-8246.0.patch
>
>
> This feature provides HDFS shell command and C/Java API to retrieve HDFS file
> name based on block pool id and block id.
> 1. The Java API in class DistributedFileSystem
> public String getFileName(String poolId, long blockId) throws IOException
> 2. The C API in hdfs.c
> char* hdfsGetFileName(hdfsFS fs, const char* poolId, int64_t blockId)
> 3. The HDFS shell command
> hdfs dfs [generic options] -fn <poolId> <blockId>
> This feature is useful if you have HDFS block file name in local file system
> and want to find out the related HDFS file name in HDFS name space
> (http://stackoverflow.com/questions/10881449/how-to-find-file-from-blockname-in-hdfs-hadoop).
> Each HDFS block file name in local file system contains both block pool id
> and block id, for sample HDFS block file name
> /hdfs/1/hadoop/hdfs/data/current/BP-97622798-10.3.11.84-1428081035160/current/finalized/subdir0/subdir0/blk_1073741825,
> the block pool id is BP-97622798-10.3.11.84-1428081035160 and the block id
> is 1073741825. The block pool id is uniquely related to a HDFS name
> node/name space, and the block id is uniquely related to a HDFS file within
> a HDFS name node/name space, so the combination of block pool id and a block
> id is uniquely related a HDFS file name.
> The shell command and C/Java API do not map the block pool id to name node,
> so it’s user’s responsibility to talk to the correct name node in federation
> environment that has multiple name nodes. The block pool id is used by name
> node to check if the user is talking with the correct name node.
> The implementation is straightforward. The client request to get HDFS file
> name reaches the new method String getFileName(String poolId, long blockId)
> in FSNamesystem in name node through RPC, and the new method does the
> followings,
> (1) Validate the block pool id.
> (2) Create Block based on the block id.
> (3) Get BlockInfoContiguous from Block.
> (4) Get BlockCollection from BlockInfoContiguous.
> (5) Get file name from BlockCollection.
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