org.apache.hadoop.hdfs.server.common

Class Storage.StorageDirectory

java.lang.Object

org.apache.hadoop.hdfs.server.common.Storage.StorageDirectory

All Implemented Interfaces:

Storage.FormatConfirmable

Enclosing class:

Storage

@InterfaceAudience.Private
public static class Storage.StorageDirectory
extends Object
implements Storage.FormatConfirmable

One of the storage directories.

Constructor Summary

Constructors

Constructor and Description
Storage.StorageDirectory(File dir)
Storage.StorageDirectory(File dir, Storage.StorageDirType dirType)
Storage.StorageDirectory(File dir, Storage.StorageDirType dirType, boolean useLock) Constructor

Method Summary

Methods

Modifier and Type	Method and Description
Storage.StorageState	analyzeStorage(HdfsServerConstants.StartupOption startOpt, Storage storage) Check consistency of the storage directory
void	clearDirectory() Clear and re-create storage directory.
void	doRecover(Storage.StorageState curState) Complete or recover storage state from previously failed transition.
File	getCurrentDir() Directory current contains latest files defining the file system meta-data.
File	getFinalizedTmp() finalized.tmp is a transient directory, which holds the previous file system state while it is being removed in response to the finalize request.
File	getLastCheckpointTmp() lastcheckpoint.tmp is a transient directory, which holds current file system state while the new state is saved into the new current during regular namespace updates.
File	getPreviousCheckpoint() previous.checkpoint is a directory, which holds the previous (before the last save) state of the storage directory.
File	getPreviousDir() Directory previous contains the previous file system state, which the system can be rolled back to.
File	getPreviousTmp() previous.tmp is a transient directory, which holds current file system state while the new state is saved into the new current during upgrade.
File	getPreviousVersionFile() File VERSION from the previous directory.
File	getRemovedTmp() removed.tmp is a transient directory, which holds current file system state while the previous state is moved into current during rollback.
File	getRoot() Get root directory of this storage
Storage.StorageDirType	getStorageDirType() Get storage directory type
File	getVersionFile() File VERSION contains the following fields: node type layout version namespaceID fs state creation time other fields specific for this node type The version file is always written last during storage directory updates.
boolean	hasSomeData()
boolean	isLockSupported() Check whether underlying file system supports file locking.
void	lock() Lock storage to provide exclusive access.
void	read(File from, Storage storage)
String	toString()
void	unlock() Unlock storage.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

Storage.StorageDirectory

public Storage.StorageDirectory(File dir)

Storage.StorageDirectory

public Storage.StorageDirectory(File dir,
                        Storage.StorageDirType dirType)

Storage.StorageDirectory

public Storage.StorageDirectory(File dir,
                        Storage.StorageDirType dirType,
                        boolean useLock)

Constructor

Parameters:

dir - directory corresponding to the storage

dirType - storage directory type

useLock - true - enables locking on the storage directory and false disables locking

Method Detail

getRoot

public File getRoot()

Get root directory of this storage

getStorageDirType

public Storage.StorageDirType getStorageDirType()

Get storage directory type

read

public void read(File from,
        Storage storage)
          throws IOException

Throws:

IOException

clearDirectory

public void clearDirectory()
                    throws IOException

Clear and re-create storage directory.

Removes contents of the current directory and creates an empty directory. This does not fully format storage directory. It cannot write the version file since it should be written last after all other storage type dependent files are written. Derived storage is responsible for setting specific storage values and writing the version file to disk.

Throws:

IOException

getCurrentDir

public File getCurrentDir()

Directory current contains latest files defining the file system meta-data.

Returns:

the directory path

getVersionFile

public File getVersionFile()

File VERSION contains the following fields:

1. node type
2. layout version
3. namespaceID
4. fs state creation time
5. other fields specific for this node type

The version file is always written last during storage directory updates. The existence of the version file indicates that all other files have been successfully written in the storage directory, the storage is valid and does not need to be recovered.

Returns:

the version file path

getPreviousVersionFile

public File getPreviousVersionFile()

File VERSION from the previous directory.

Returns:

the previous version file path

getPreviousDir

public File getPreviousDir()

Directory previous contains the previous file system state, which the system can be rolled back to.

Returns:

the directory path

getPreviousTmp

public File getPreviousTmp()

previous.tmp is a transient directory, which holds current file system state while the new state is saved into the new current during upgrade. If the saving succeeds previous.tmp will be moved to previous, otherwise it will be renamed back to current by the recovery procedure during startup.

Returns:

the directory path

getRemovedTmp

public File getRemovedTmp()

removed.tmp is a transient directory, which holds current file system state while the previous state is moved into current during rollback. If the moving succeeds removed.tmp will be removed, otherwise it will be renamed back to current by the recovery procedure during startup.

Returns:

the directory path

getFinalizedTmp

public File getFinalizedTmp()

finalized.tmp is a transient directory, which holds the previous file system state while it is being removed in response to the finalize request. Finalize operation will remove finalized.tmp when completed, otherwise the removal will resume upon the system startup.

Returns:

the directory path

getLastCheckpointTmp

public File getLastCheckpointTmp()

lastcheckpoint.tmp is a transient directory, which holds current file system state while the new state is saved into the new current during regular namespace updates. If the saving succeeds lastcheckpoint.tmp will be moved to previous.checkpoint, otherwise it will be renamed back to current by the recovery procedure during startup.

Returns:

the directory path

getPreviousCheckpoint

public File getPreviousCheckpoint()

previous.checkpoint is a directory, which holds the previous (before the last save) state of the storage directory. The directory is created as a reference only, it does not play role in state recovery procedures, and is recycled automatically, but it may be useful for manual recovery of a stale state of the system.

Returns:

the directory path

analyzeStorage

public Storage.StorageState analyzeStorage(HdfsServerConstants.StartupOption startOpt,
                                  Storage storage)
                                    throws IOException

Check consistency of the storage directory

Parameters:

startOpt - a startup option.

Returns:

state Storage.StorageState of the storage directory

Throws:

InconsistentFSStateException - if directory state is not consistent and cannot be recovered.

IOException

doRecover

public void doRecover(Storage.StorageState curState)
               throws IOException

Complete or recover storage state from previously failed transition.

Parameters:

curState - specifies what/how the state should be recovered

Throws:

IOException

hasSomeData

public boolean hasSomeData()
                    throws IOException

Specified by:

hasSomeData in interface Storage.FormatConfirmable

Returns:

true if the storage directory should prompt the user prior to formatting (i.e if the directory appears to contain some data)

Throws:

IOException - if the SD cannot be accessed due to an IO error

lock

public void lock()
          throws IOException

Lock storage to provide exclusive access.

Locking is not supported by all file systems. E.g., NFS does not consistently support exclusive locks.

If locking is supported we guarantee exclusive access to the storage directory. Otherwise, no guarantee is given.

Throws:

IOException - if locking fails

unlock

public void unlock()
            throws IOException

Unlock storage.

Throws:

IOException

toString

public String toString()

Specified by:

toString in interface Storage.FormatConfirmable

Overrides:

toString in class Object

Returns:

a string representation of the formattable item, suitable for display to the user inside a prompt

isLockSupported

public boolean isLockSupported()
                        throws IOException

Check whether underlying file system supports file locking.

Returns:

true if exclusive locks are supported or false otherwise.

Throws:

IOException

See Also:

lock()