Kai Zheng created HDFS-9705:
-------------------------------
Summary: Refine the behaviour of getFileChecksum when length = 0
Key: HDFS-9705
URL: https://issues.apache.org/jira/browse/HDFS-9705
Project: Hadoop HDFS
Issue Type: Improvement
Reporter: Kai Zheng
Assignee: Kai Zheng
Priority: Minor
{{FileSystem#getFileChecksum}} may accept {{length}} parameter and 0 is a valid
value. Currently it will return {{null}} when length is 0, in the following
code block:
{code}
//compute file MD5
final MD5Hash fileMD5 = MD5Hash.digest(md5out.getData());
switch (crcType) {
case CRC32:
return new MD5MD5CRC32GzipFileChecksum(bytesPerCRC,
crcPerBlock, fileMD5);
case CRC32C:
return new MD5MD5CRC32CastagnoliFileChecksum(bytesPerCRC,
crcPerBlock, fileMD5);
default:
// If there is no block allocated for the file,
// return one with the magic entry that matches what previous
// hdfs versions return.
if (locatedblocks.size() == 0) {
return new MD5MD5CRC32GzipFileChecksum(0, 0, fileMD5);
}
// we should never get here since the validity was checked
// when getCrcType() was called above.
return null;
}
{code}
The comment says "we should never get here since the validity was checked" but
it does. As we're using the MD5-MD5-X approach, and {{EMPTY--CONTENT}} actually
is a valid case in which the MD5 value is {{d41d8cd98f00b204e9800998ecf8427e}},
so suggest we return a reasonable value other than null. At least some useful
information in the returned value can be seen, like values from block checksum
header.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
