Package org.apache.hadoop.dfs

A distributed implementation of FileSystem.

See:
Description

Interface Summary

FSConstants	Some handy constants
FSDatasetInterface	This is an interface for the underlying storage that stores blocks for a data node.
Upgradeable	Common interface for distributed upgrade objects.

Class Summary

Balancer	The balancer is a tool that balances disk space usage on an HDFS cluster when some datanodes become full or when new empty nodes join the cluster.
ChecksumDistributedFileSystem	An implementation of ChecksumFileSystem over DistributedFileSystem.
DataBlockScanner
DataBlockScanner.Servlet
DataChecksum	This class provides inteface and utilities for processing checksums for DFS data transfers.
DataNode	DataNode is a class (and program) that stores a set of blocks for a DFS deployment.
DatanodeDescriptor	DatanodeDescriptor tracks stats on a given DataNode, such as available storage capacity, last update time, etc., and maintains a set of blocks stored on the datanode.
DatanodeID	DatanodeID is composed of the data node name (hostname:portNumber) and the data storage ID, which it currently represents.
DatanodeInfo	DatanodeInfo represents the status of a DataNode.
DFSAdmin	This class provides some DFS administrative access.
DFSck	This class provides rudimentary checking of DFS volumes for errors and sub-optimal conditions.
DistributedFileSystem	Implementation of the abstract FileSystem for the DFS system.
DistributedFileSystem.DiskStatus
FileDataServlet	Redirect queries about the hosted filesystem to an appropriate datanode.
FsckServlet	This class is used in Namesystem's jetty to do fsck on namenode.
FSDatasetInterface.BlockWriteStreams	This class contains the output streams for the data and checksum of a block
FSDatasetInterface.MetaDataInputStream	This class provides the input stream and length of the metadata of a block
FSNamesystemMetrics	This class is for maintaining the various FSNamesystem status metrics and publishing them through the metrics interfaces.
GetImageServlet	This class is used in Namesystem's jetty to retrieve a file.
HftpFileSystem	An implementation of a protocol for accessing filesystems over HTTP.
HsftpFileSystem	An implementation of a protocol for accessing filesystems over HTTPS.
JspHelper
ListPathsServlet	Obtain meta-information about a filesystem.
LocatedBlocks	Collection of blocks with their locations and the file length.
NameNode	NameNode serves as both directory namespace manager and "inode table" for the Hadoop DFS.
NamenodeFsck	This class provides rudimentary checking of DFS volumes for errors and sub-optimal conditions.
NamenodeFsck.FsckResult	FsckResult of checking, plus overall DFS statistics.
NameNodeMetrics	This class is for maintaining the various NameNode statistics and publishing them through the metrics interfaces.
SecondaryNameNode	The Secondary NameNode is a helper to the primary NameNode.
StreamFile
UpgradeStatusReport	Base upgrade upgradeStatus class.

Enum Summary

DatanodeInfo.AdminStates
FSConstants.CheckpointStates
FSConstants.DatanodeReportType
FSConstants.NodeType	Type of the node
FSConstants.SafeModeAction
FSConstants.StartupOption
FSConstants.UpgradeAction	Distributed upgrade actions: 1.

Exception Summary

AlreadyBeingCreatedException	The exception that happens when you ask to create a file that already is being created, but is not closed yet.
LeaseExpiredException	The lease that was being used to create this file has expired.
NotReplicatedYetException	The file has not finished being written to enough datanodes yet.
QuotaExceededException	This class is for the error when an attempt to add an inode to namespace violates the quota restriction of any inode on the path to the newly added inode.
SafeModeException	This exception is thrown when the name node is in safe mode.

Package org.apache.hadoop.dfs Description

A distributed implementation of FileSystem. This is loosely modelled after Google's GFS.

The most important difference is that unlike GFS, Hadoop DFS files have strictly one writer at any one time. Bytes are always appended to the end of the writer's stream. There is no notion of "record appends" or "mutations" that are then checked or reordered. Writers simply emit a byte stream. That byte stream is guaranteed to be stored in the order written.