[HDFS-8224] Schedule a block for scanning if its metadata file is corrupt

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.6.0
• Fix Version/s: 2.8.0, 2.7.4, 3.0.0-alpha1
• Component/s: datanode
• Target Version/s: 2.8.0
• Hadoop Flags: Reviewed
• Assignee: Rushabh Shah
• Reporter: Rushabh Shah
• Created: 22/Apr/15 19:51
• Updated: 07/Apr/21 02:43
• Resolved: 10/Aug/16 18:43

Description

This happened in our 2.6 cluster.
One of the block and its metadata file were corrupted.
The disk was healthy in this case.
Only the block was corrupt.

Namenode tried to copy that block to another datanode but failed with the following stack trace:

2015-04-20 01:04:04,421 [org.apache.hadoop.hdfs.server.datanode.DataNode$DataTransfer@11319bc4] WARN datanode.DataNode: DatanodeRegistration(a.b.c.d, datanodeUuid=e8c5135c-9b9f-4d05-a59d-e5525518aca7, infoPort=1006, infoSecurePort=0, ipcPort=8020, storageInfo=lv=-56;cid=CID-e7f736ac-158e-446e-9091-7e66f3cddf3c;nsid=358250775;c=1428471998571):Failed to transfer BP-xxx-1351096255769:blk_2697560713_1107108863999 to a1.b1.c1.d1:1004 got
java.io.IOException: Could not create DataChecksum of type 0 with bytesPerChecksum 0
at org.apache.hadoop.util.DataChecksum.newDataChecksum(DataChecksum.java:125)
at org.apache.hadoop.hdfs.server.datanode.BlockMetadataHeader.readHeader(BlockMetadataHeader.java:175)
at org.apache.hadoop.hdfs.server.datanode.BlockMetadataHeader.readHeader(BlockMetadataHeader.java:140)
at org.apache.hadoop.hdfs.server.datanode.BlockMetadataHeader.readDataChecksum(BlockMetadataHeader.java:102)
at org.apache.hadoop.hdfs.server.datanode.BlockSender.<init>(BlockSender.java:287)
at org.apache.hadoop.hdfs.server.datanode.DataNode$DataTransfer.run(DataNode.java:1989)
at java.lang.Thread.run(Thread.java:722)

The following catch block in DataTransfer#run method will treat every IOException as disk error fault and run disk errror

catch (IOException ie) {
        LOG.warn(bpReg + ":Failed to transfer " + b + " to " +
            targets[0] + " got ", ie);
        // check if there are any disk problem
        checkDiskErrorAsync();
      } 

This block was never scanned by BlockPoolSliceScanner otherwise it would have reported as corrupt block.