feng xu created HDFS-8246:
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Summary: 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
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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