[HDFS-4380] Opening a file for read before writer writes a block causes NPE

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 1.0.3
• Assignee: Unassigned
• Reporter: Todd Lipcon
• Created: 10/Jan/13 00:20
• Updated: 13/Mar/13 22:48

Description

JD Cryans found this issue: it seems like, if you open a file for read immediately after it's been created by the writer, after a block has been allocated, but before the block is created on the DNs, then you can end up with the following NPE:

java.lang.NullPointerException
at org.apache.hadoop.hdfs.DFSClient$DFSInputStream.updateBlockInfo(DFSClient.java:1885)
at org.apache.hadoop.hdfs.DFSClient$DFSInputStream.openInfo(DFSClient.java:1858)
at org.apache.hadoop.hdfs.DFSClient$DFSInputStream.<init>(DFSClient.java:1834)
at org.apache.hadoop.hdfs.DFSClient.open(DFSClient.java:578)
at org.apache.hadoop.hdfs.DistributedFileSystem.open(DistributedFileSystem.java:154)

This seems to be because getBlockInfo returns a null block when the DN doesn't yet have the replica. The client should probably either fall back to a different replica or treat it as zero-length.

Issue Links

• is related to: HBASE-8096 [replication] NPE while replicating a log that is acquiring a new block from HDFS
• relates to: HDFS-3533 NPE in DFSClient$DFSInputStream.openInfo
• relates to: HDFS-3222 DFSInputStream#openInfo should not silently get the length as 0 when locations length is zero for last partial block.