[HDFS-6908] incorrect snapshot directory diff generated by snapshot deletion

• Type: Bug
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Fix Version/s: 2.6.0
• Component/s: snapshots
• Hadoop Flags: Reviewed
• Assignee: Juan Yu
• Reporter: Juan Yu
• Created: 21/Aug/14 20:29
• Updated: 16/Sep/15 18:22
• Resolved: 27/Aug/14 17:30

Description

In the following scenario, delete snapshot could generate incorrect snapshot directory diff and corrupted fsimage, if you restart NN after that, you will get NullPointerException.
1. create a directory and create a file under it
2. take a snapshot
3. create another file under that directory
4. take second snapshot
5. delete both files and the directory
6. delete second snapshot
incorrect directory diff will be generated.

Restart NN will throw NPE

java.lang.NullPointerException
	at org.apache.hadoop.hdfs.server.namenode.snapshot.FSImageFormatPBSnapshot$Loader.addToDeletedList(FSImageFormatPBSnapshot.java:246)
	at org.apache.hadoop.hdfs.server.namenode.snapshot.FSImageFormatPBSnapshot$Loader.loadDeletedList(FSImageFormatPBSnapshot.java:265)
	at org.apache.hadoop.hdfs.server.namenode.snapshot.FSImageFormatPBSnapshot$Loader.loadDirectoryDiffList(FSImageFormatPBSnapshot.java:328)
	at org.apache.hadoop.hdfs.server.namenode.snapshot.FSImageFormatPBSnapshot$Loader.loadSnapshotDiffSection(FSImageFormatPBSnapshot.java:192)
	at org.apache.hadoop.hdfs.server.namenode.FSImageFormatProtobuf$Loader.loadInternal(FSImageFormatProtobuf.java:254)
	at org.apache.hadoop.hdfs.server.namenode.FSImageFormatProtobuf$Loader.load(FSImageFormatProtobuf.java:168)
	at org.apache.hadoop.hdfs.server.namenode.FSImageFormat$LoaderDelegator.load(FSImageFormat.java:208)
	at org.apache.hadoop.hdfs.server.namenode.FSImage.loadFSImage(FSImage.java:906)
	at org.apache.hadoop.hdfs.server.namenode.FSImage.loadFSImage(FSImage.java:892)
	at org.apache.hadoop.hdfs.server.namenode.FSImage.loadFSImageFile(FSImage.java:715)
	at org.apache.hadoop.hdfs.server.namenode.FSImage.loadFSImage(FSImage.java:653)
	at org.apache.hadoop.hdfs.server.namenode.FSImage.recoverTransitionRead(FSImage.java:276)
	at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.loadFSImage(FSNamesystem.java:882)
	at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.loadFromDisk(FSNamesystem.java:629)
	at org.apache.hadoop.hdfs.server.namenode.NameNode.loadNamesystem(NameNode.java:498)
	at org.apache.hadoop.hdfs.server.namenode.NameNode.initialize(NameNode.java:554)

Issue Links

• is duplicated by: HDFS-9052 deleteSnapshot runs into AssertionError