Abhishek Rai created HDFS-6431:
----------------------------------
Summary: File in snapshot tree is not readable due to null blocks
Key: HDFS-6431
URL: https://issues.apache.org/jira/browse/HDFS-6431
Project: Hadoop HDFS
Issue Type: Bug
Components: namenode, snapshots
Affects Versions: 2.2.0
Environment: 2-node HDFS setup with hadoop-2.2.0.
Namenode on node A and datanode on both nodes, A and B.
Reporter: Abhishek Rai
Steps:
1. Took a snapshot of HDFS directory:
/orion/dogfood/
2. Snapshot was successful.
/orion/dogfood/.snapshot/20140517/
3. Initiated copy of the snapshotted directory
hadoop-2.2.0/bin/hdfs dfs -fs 192.168.2.239 -get
/orion/dogfood/.snapshot/20140517 ~/tmp/copy
4. Normally, this succeeds. We have copied numerous (other) snapshots of this
directory in the past. But copying this particular snapshot gives the
following error:
get: Cannot open filename
/orion/dogfood/.snapshot/20140517/cache/log-dogfood-20140513.111409-466b34cd-a488-4bd9-b1f2-a9f280e647c2
Above "hdfs -get" command fails with exit status 1. Interestingly, this file
was skipped and all other good files were copied.
5. The file has zero length --
$ hadoop-2.2.0/bin/hdfs 192.168.2.239 -ls
/orion/dogfood/.snapshot/20140517/cache/log-dogfood-20140514.133924-132c3165-55c3-4908-ac19-31c61922205f
-rw-r--r-- 3 admin admin 0 2014-05-14 13:39
/orion/dogfood/.snapshot/20140517/cache/log-dogfood-20140514.133924-132c3165-55c3-4908-ac19-31c61922205f
6. Trying to copy this file individually also gives same error --
$ hadoop-2.2.0/bin/hdfs 192.168.2.239 -get
/orion/dogfood/.snapshot/20140517/cache/log-dogfood-20140514.133924-132c3165-55c3-4908-ac19-31c61922205f
/tmp/file
get: Cannot open filename
/orion/dogfood/.snapshot/20140517/cache/log-dogfood-20140514.133924-132c3165-55c3-4908-ac19-31c61922205f
This seems like a bug to me. From looking at HDFS code, I made the following
observations:
o DFSInputStream is receiving null "LocatedBlocks" for the source file:
final LocatedBlocks newInfo = dfsClient.getLocatedBlocks(src, 0);
o This would happen when server returns GetLocatedBlocksResponse with
"locations" not set, which can happen only if INodeFile.blocks is null for the
file being opened.
So, it appears that for this file, blocks is null in this snapshot.
--
This message was sent by Atlassian JIRA
(v6.2#6252)
