Srinivasu Majeti created HDFS-16215:
---------------------------------------

             Summary: File read fails with CannotObtainBlockLengthException 
after Namenode is restarted
                 Key: HDFS-16215
                 URL: https://issues.apache.org/jira/browse/HDFS-16215
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: datanode
    Affects Versions: 3.3.1, 3.2.2
            Reporter: Srinivasu Majeti


When a file is being written by first client and fsck shows OPENFORWRITE and 
HDFS outage happens and brough back up , first client is disconnected and a new 
client tries to open the file we see "Cannot obtain block length for"  as shown 
below.

{code:java}
/tmp/hosts7 134217728 bytes, replicated: replication=3, 1 block(s), 
OPENFORWRITE:  OK
0. BP-1958960150-172.25.40.87-1628677864204:blk_1073745252_4430 len=134217728 
Live_repl=3  
[DatanodeInfoWithStorage[172.25.36.14:9866,DS-6357ab37-84ae-4c7c-8794-fef905bcde05,DISK],
 
DatanodeInfoWithStorage[172.25.33.132:9866,DS-92e75140-d066-4ab5-b250-dbfd329289c5,DISK],
 
DatanodeInfoWithStorage[172.25.40.70:9866,DS-1e280bcd-a2ce-4320-9ebb-33fc903d3a47,DISK]]

Under Construction Block:
1. BP-1958960150-172.25.40.87-1628677864204:blk_1073745253_4431 len=0 
Expected_repl=3  
[DatanodeInfoWithStorage[172.25.36.14:9866,DS-6357ab37-84ae-4c7c-8794-fef905bcde05,DISK],
 
DatanodeInfoWithStorage[172.25.33.132:9866,DS-92e75140-d066-4ab5-b250-dbfd329289c5,DISK],
 
DatanodeInfoWithStorage[172.25.40.70:9866,DS-1e280bcd-a2ce-4320-9ebb-33fc903d3a47,DISK]]

[root@c1265-node2 ~]# hdfs dfs -get /tmp/hosts7
get: Cannot obtain block length for 
LocatedBlock{BP-1958960150-172.25.40.87-1628677864204:blk_1073745253_4431; 
getBlockSize()=0; corrupt=false; offset=134217728; 
locs=[DatanodeInfoWithStorage[172.25.40.70:9866,DS-1e280bcd-a2ce-4320-9ebb-33fc903d3a47,DISK],
 
DatanodeInfoWithStorage[172.25.33.132:9866,DS-92e75140-d066-4ab5-b250-dbfd329289c5,DISK],
 
DatanodeInfoWithStorage[172.25.36.14:9866,DS-6357ab37-84ae-4c7c-8794-fef905bcde05,DISK]]}

*Exception trace from the logs:*

Exception in thread "main" 
org.apache.hadoop.hdfs.CannotObtainBlockLengthException: Cannot obtain block 
length for 
LocatedBlock{BP-1958960150-172.25.40.87-1628677864204:blk_1073742720_1896; 
getBlockSize()=0; corrupt=false; offset=134217728; 
locs=[DatanodeInfoWithStorage[172.25.33.140:9866,DS-92e75140-d066-4ab5-b250-dbfd329289c5,DISK],
 
DatanodeInfoWithStorage[172.25.40.87:9866,DS-1e280bcd-a2ce-4320-9ebb-33fc903d3a47,DISK],
 
DatanodeInfoWithStorage[172.25.36.17:9866,DS-6357ab37-84ae-4c7c-8794-fef905bcde05,DISK]]}
        at 
org.apache.hadoop.hdfs.DFSInputStream.readBlockLength(DFSInputStream.java:363)
        at 
org.apache.hadoop.hdfs.DFSInputStream.fetchLocatedBlocksAndGetLastBlockLength(DFSInputStream.java:270)
        at 
org.apache.hadoop.hdfs.DFSInputStream.openInfo(DFSInputStream.java:201)
        at org.apache.hadoop.hdfs.DFSInputStream.<init>(DFSInputStream.java:185)
        at org.apache.hadoop.hdfs.DFSClient.open(DFSClient.java:1006)
        at 
org.apache.hadoop.hdfs.DistributedFileSystem$4.doCall(DistributedFileSystem.java:316)
        at 
org.apache.hadoop.hdfs.DistributedFileSystem$4.doCall(DistributedFileSystem.java:312)
        at 
org.apache.hadoop.fs.FileSystemLinkResolver.resolve(FileSystemLinkResolver.java:81)
        at 
org.apache.hadoop.hdfs.DistributedFileSystem.open(DistributedFileSystem.java:324)
        at org.apache.hadoop.fs.FileSystem.open(FileSystem.java:949)
{code}




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