galileo.fs

Class FileSystem

java.lang.Object

galileo.fs.FileSystem

All Implemented Interfaces:

PhysicalGraph

Direct Known Subclasses:

GeospatialFileSystem

public abstract class FileSystem
extends java.lang.Object
implements PhysicalGraph

Field Summary

Fields

Modifier and Type	Field and Description
static java.lang.String	BLOCK_EXTENSION
protected java.io.File	storageDirectory

Constructor Summary

Constructors

Constructor and Description
FileSystem(java.lang.String storageRoot)

Method Summary

Modifier and Type	Method and Description
protected void	fullRecovery() Does a full recovery from disk; this scans every block in the system, reads metadata, and performs a checksum to verify integrity.
long	getFreeSpace() Reports the amount of free space (in bytes) in the root storage directory.
protected void	initialize(java.lang.String storageRoot)
boolean	isReadOnly() Reports whether the Galileo filesystem is read-only.
Block	loadBlock(java.lang.String blockPath) Retrieves a Block instance, given its path on disk.
Metadata	loadMetadata(java.lang.String blockPath) Retrieves a Metadata instance, given a Block path on disk.
protected java.util.List<java.lang.String>	rebuildPaths(java.io.File storageDir) Scans the directory structure on disk to find all the blocks stored.
protected void	recover(java.util.List<java.lang.String> blockPaths) Does a full recovery from disk on a particular Galileo partition; this scans every block in the partition, reads its metadata, and performs a checksum to verify block integrity.
protected java.util.List<java.lang.String>	scanDirectory(java.io.File directory) Scans a directory (and its subdirectories) for blocks.
abstract void	shutdown() Performs a clean shutdown of the FileSystem instance.
java.lang.String	storeBlock(Block block) Stores a Block on disk.
abstract void	storeMetadata(Metadata metadata, java.lang.String blockPath) Inserts Metadata into the file system.

Methods inherited from class java.lang.Object

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

Field Detail

BLOCK_EXTENSION

public static final java.lang.String BLOCK_EXTENSION

See Also:

Constant Field Values

storageDirectory

protected java.io.File storageDirectory

Constructor Detail

FileSystem

public FileSystem(java.lang.String storageRoot)
           throws FileSystemException,
                  java.io.IOException

Throws:

FileSystemException

java.io.IOException

Method Detail

initialize

protected void initialize(java.lang.String storageRoot)
                   throws FileSystemException,
                          java.io.IOException

Throws:

FileSystemException

java.io.IOException

scanDirectory

protected java.util.List<java.lang.String> scanDirectory(java.io.File directory)

Scans a directory (and its subdirectories) for blocks.

Parameters:

directory - Directory to scan for blocks.

Returns:

ArrayList of String paths to blocks on disk.

fullRecovery

protected void fullRecovery()

Does a full recovery from disk; this scans every block in the system, reads metadata, and performs a checksum to verify integrity. If not already obvious, this could be very slow.

rebuildPaths

protected java.util.List<java.lang.String> rebuildPaths(java.io.File storageDir)

Scans the directory structure on disk to find all the blocks stored.

Parameters:

storageDir - the root directory to start scanning from.

recover

protected void recover(java.util.List<java.lang.String> blockPaths)

Does a full recovery from disk on a particular Galileo partition; this scans every block in the partition, reads its metadata, and performs a checksum to verify block integrity.

loadBlock

public Block loadBlock(java.lang.String blockPath)
                throws java.io.IOException,
                       galileo.serialization.SerializationException

Description copied from interface: PhysicalGraph

Retrieves a Block instance, given its path on disk.

Specified by:

loadBlock in interface PhysicalGraph

Parameters:

blockPath - the physical (on-disk) location of the Block to load.

Returns:

Block stored at blockPath.

Throws:

java.io.IOException

galileo.serialization.SerializationException

loadMetadata

public Metadata loadMetadata(java.lang.String blockPath)
                      throws java.io.IOException,
                             galileo.serialization.SerializationException

Description copied from interface: PhysicalGraph

Retrieves a Metadata instance, given a Block path on disk.

Specified by:

loadMetadata in interface PhysicalGraph

Parameters:

blockPath - the physical location of the Block to load metadata from.

Returns:

Metadata stored in the Block specified by blockPath.

Throws:

java.io.IOException

galileo.serialization.SerializationException

storeBlock

public java.lang.String storeBlock(Block block)
                            throws FileSystemException,
                                   java.io.IOException

Description copied from interface: PhysicalGraph

Stores a Block on disk. The location of the Block will be determined by the particular FileSystem implementation being used rather than as a method parameter, so only the Block itself is provided.

Specified by:

storeBlock in interface PhysicalGraph

Parameters:

block - the Block instance to persist to disk.

Returns:

String representation of the Block path on disk.

Throws:

FileSystemException

java.io.IOException

storeMetadata

public abstract void storeMetadata(Metadata metadata,
                                   java.lang.String blockPath)
                            throws FileSystemException,
                                   java.io.IOException

Description copied from interface: PhysicalGraph

Inserts Metadata into the file system. In many cases, Metadata is not stored individually on disk but placed in an index instead. This method is useful during a full recovery operation for re-linking indexed Metadata with its associated files on disk, or could be used in situations where information should only be indexed and not stored.

Specified by:

storeMetadata in interface PhysicalGraph

Parameters:

metadata - the Metadata to 'store,' which may just involve updating index structures.

blockPath - the on-disk path of the Block the Metadata being stored belongs to.

Throws:

FileSystemException

java.io.IOException

isReadOnly

public boolean isReadOnly()

Reports whether the Galileo filesystem is read-only.

Returns:

true if the filesystem is read-only.

getFreeSpace

public long getFreeSpace()

Reports the amount of free space (in bytes) in the root storage directory.

Returns:

long integer with the amount of free space, in bytes.

shutdown

public abstract void shutdown()

Performs a clean shutdown of the FileSystem instance. This includes flushing buffers, writing changes out to disk, persisting index structures, etc.

Note that this method may be called during a signal handling operation, which may mean that the logging subsystem has already shut down, so critical errors/information should be printed to stdout or stderr. Furthermore, there is no guarantee all the shutdown operations will be executed, so time is of the essence here.