NullPointerException in DataInputStream.readInt
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Key: HDFS-1459
URL: https://issues.apache.org/jira/browse/HDFS-1459
Project: Hadoop HDFS
Issue Type: Bug
Affects Versions: 0.20.1
Environment: Debian 64 bit
Cloudera Hadoop
Reporter: Hajo Nils Krabbenhöft
First, here's my source code accessing the HDFS:
final FSDataInputStream indexFile = getFile(bucketPathStr,
Integer.toString(hashTableId) + ".index");
indexFile.seek(bucketId * 4);
int bucketStart = ByteSwapper.swap(indexFile.readInt());
int bucketEnd = ByteSwapper.swap(indexFile.readInt());
final FSDataInputStream dataFile = getFile(bucketPathStr,
Integer.toString(hashTableId) + ".data");
dataFile.seek(bucketStart * (2 + Hasher.getConfigHashLength()) * 4);
for (int hash = bucketStart; hash < bucketEnd; hash++) {
int RimageIdA = ByteSwapper.swap(dataFile.readInt());
int RimageIdB = ByteSwapper.swap(dataFile.readInt());
....... read hash of length Hasher.getConfigHashLength() and work with
it ....
}
As you can see, i am reading the range to be read from an X.index file and then
read these rows from X.data. The index file is always exactly 6.710.888 bytes
in length.
As for the data file, everything works fine with 50 different 1.35 GB (22
blocks) data files and it fails every time i tried with 50 different 2.42 GB
(39 blocks) data files. So the cause of the bug is clearly dependent on the
file size.
I checked for ulimit and for the number of network connections and they are
both not maxed out when the error occurs. The stack trace i get is:
java.lang.NullPointerException
at
org.apache.hadoop.hdfs.DFSClient$DFSInputStream.readBuffer(DFSClient.java:1703)
at
org.apache.hadoop.hdfs.DFSClient$DFSInputStream.read(DFSClient.java:1755)
at
org.apache.hadoop.hdfs.DFSClient$DFSInputStream.read(DFSClient.java:1680)
at java.io.DataInputStream.readInt(DataInputStream.java:370)
...
at org.apache.hadoop.mapred.MapRunner.run(MapRunner.java:50)
at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:358)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:307)
at org.apache.hadoop.mapred.Child.main(Child.java:170)
which leads me to believe that DFSClient.blockSeekTo returns with a non-null
chosenNode but with blockReader = null.
Since the exact same jar works flawlessly with small data files and fails
reliably with big data files, i'm wondering how this could possibly dependent
on the file's size or block count (DFSClient.java line 1628+):
s = socketFactory.createSocket();
NetUtils.connect(s, targetAddr, socketTimeout);
s.setSoTimeout(socketTimeout);
Block blk = targetBlock.getBlock();
blockReader = BlockReader.newBlockReader(s, src, blk.getBlockId(),
blk.getGenerationStamp(),
offsetIntoBlock, blk.getNumBytes() - offsetIntoBlock,
buffersize, verifyChecksum, clientName);
return chosenNode;
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