[HADOOP-12326] Implement ChecksumFileSystem#getFileChecksum equivalent to HDFS for easy check

• Type: Improvement
• Status: Patch Available
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 2.7.1
• Component/s: fs
• Target Version/s: 2.8.3
• Assignee: Gera Shegalov
• Reporter: Gera Shegalov
• Created: 15/Aug/15 20:30
• Updated: 11/Sep/17 05:39

Description

If we have same-content files, one local and one remotely on HDFS (after downloading or uploading), getFileChecksum can provide a quick check whether they are consistent. To this end, we can switch to CRC32C on local filesystem. The difference in block sizes does not matter, because for the local filesystem it's just a logical parameter.

$ hadoop fs -Dfs.local.block.size=134217728 -checksum file:${PWD}/part-m-00000 part-m-00000
15/08/15 13:30:02 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
file:///Users/gshegalov/workspace/hadoop-common/part-m-00000	MD5-of-262144MD5-of-512CRC32C	000002000000000000040000e84fb07f8c9d4ef3acb5d1983a7e2a68
part-m-00000	MD5-of-262144MD5-of-512CRC32C	000002000000000000040000e84fb07f8c9d4ef3acb5d1983a7e2a68