Stephen O'Donnell created HDFS-16496:
----------------------------------------
Summary: Snapshot diff on snapshotable directory fails with not
snapshottable error
Key: HDFS-16496
URL: https://issues.apache.org/jira/browse/HDFS-16496
Project: Hadoop HDFS
Issue Type: Bug
Reporter: Stephen O'Donnell
Assignee: Stephen O'Donnell
Running a snapshot diff against some snapshotable folders gives an error:
{code}
org.apache.hadoop.hdfs.protocol.SnapshotException: Directory is neither
snapshottable nor under a snap root!
at
org.apache.hadoop.hdfs.server.namenode.snapshot.SnapshotManager.checkAndGetSnapshottableAncestorDir(SnapshotManager.java:395)
at
org.apache.hadoop.hdfs.server.namenode.snapshot.SnapshotManager.diff(SnapshotManager.java:744)
at
org.apache.hadoop.hdfs.server.namenode.FSDirSnapshotOp.getSnapshotDiffReportListing(FSDirSnapshotOp.java:200)
at
org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getSnapshotDiffReportListing(FSNamesystem.java:6983)
at
org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.getSnapshotDiffReportListing(NameNodeRpcServer.java:1977)
at
org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.getSnapshotDiffReportListing(ClientNamenodeProtocolServerSideTranslatorPB.java:1387)
at
org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java)
at
org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:533)
at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:1070)
at org.apache.hadoop.ipc.Server$RpcCall.run(Server.java:989)
at org.apache.hadoop.ipc.Server$RpcCall.run(Server.java:917)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:422)
at
org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1898)
at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2894)
{code}
This is caused by HDFS-15483 (in order snapshot delete), and the issue is in
the following method in SnapshotManager:
{code}
public INodeDirectory getSnapshottableAncestorDir(final INodesInPath iip)
throws IOException {
final String path = iip.getPath();
final INode inode = iip.getLastINode();
final INodeDirectory dir;
if (inode instanceof INodeDirectory) { // THIS SHOULD BE TRUE - change to
inode.isDirectory()
dir = INodeDirectory.valueOf(inode, path);
} else {
dir = INodeDirectory.valueOf(iip.getINode(-2), iip.getParentPath());
}
if (dir.isSnapshottable()) {
return dir;
}
for (INodeDirectory snapRoot : this.snapshottables.values()) {
if (dir.isAncestorDirectory(snapRoot)) {
return snapRoot;
}
}
return null;
}
{code}
After adding some debug, I found the directory which is the snapshot root is
not an instance of INodeDirectory, but instead is an
"INodeReference$DstReference". I think the directory becomes an instance of
this class, if the directory is renamed and one of its children has been moved
out of another snapshot.
The fix is simple - just check `inode.isDirectory()` instead.
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