storage

Class StorageServer

java.lang.Object

storage.StorageServer

All Implemented Interfaces:

Command, Storage

Direct Known Subclasses:

StorageServerApp.StoppingStorageServer

public class StorageServer
extends java.lang.Object
implements Storage, Command

Storage server.

Storage servers respond to client file access requests. The files accessible through a storage server are those accessible under a given directory of the local filesystem.

Field Summary

Fields

Modifier and Type	Field and Description
(package private) Skeleton<Command>	commandSkeleton
private java.io.File	root
(package private) Skeleton<Storage>	storageSkeleton

Constructor Summary

Constructors

Constructor and Description
StorageServer(java.io.File root) Creates a storage server, given a directory on the local filesystem.

Method Summary

Modifier and Type	Method and Description
boolean	copy(Path file, Storage server) Copies a file from another storage server.
boolean	create(Path file) Creates a file on the storage server.
boolean	delete(Path path) Deletes a file or directory on the storage server.
private java.lang.Boolean	deleteHelper(java.io.File f)
private void	directoryCleanup(java.io.File root)
byte[]	read(Path file, long offset, int length) Reads a sequence of bytes from a file.
long	size(Path file) Returns the length of a file, in bytes.
void	start(java.lang.String hostname, Registration naming_server) Starts the storage server and registers it with the given naming server.
void	stop() Stops the storage server.
protected void	stopped(java.lang.Throwable cause) Called when the storage server has shut down.
void	write(Path file, long offset, byte[] data) Writes bytes to a file.

Methods inherited from class java.lang.Object

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

Field Detail

root

private java.io.File root

storageSkeleton

Skeleton<Storage> storageSkeleton

commandSkeleton

Skeleton<Command> commandSkeleton

Constructor Detail

StorageServer

public StorageServer(java.io.File root)

Creates a storage server, given a directory on the local filesystem.

Parameters:

root - Directory on the local filesystem. The contents of this directory will be accessible through the storage server.

Throws:

java.lang.NullPointerException - If root is null.

Method Detail

start

public void start(java.lang.String hostname,
                  Registration naming_server)
           throws RMIException,
                  java.net.UnknownHostException,
                  java.io.FileNotFoundException

Starts the storage server and registers it with the given naming server.

Parameters:

hostname - The externally-routable hostname of the local host on which the storage server is running. This is used to ensure that the stub which is provided to the naming server by the start method carries the externally visible hostname or address of this storage server.

naming_server - Remote interface for the naming server with which the storage server is to register.

Throws:

java.net.UnknownHostException - If a stub cannot be created for the storage server because a valid address has not been assigned.

java.io.FileNotFoundException - If the directory with which the server was created does not exist or is in fact a file.

RMIException - If the storage server cannot be started, or if it cannot be registered.

directoryCleanup

private void directoryCleanup(java.io.File root)

stop

public void stop()

Stops the storage server.

The server should not be restarted.

stopped

protected void stopped(java.lang.Throwable cause)

Called when the storage server has shut down.

Parameters:

cause - The cause for the shutdown, if any, or null if the server was shut down by the user's request.

size

public long size(Path file)
          throws java.io.FileNotFoundException,
                 RMIException

Description copied from interface: Storage

Returns the length of a file, in bytes.

Specified by:

size in interface Storage

Parameters:

file - Path to the file.

Returns:

The length of the file.

Throws:

java.io.FileNotFoundException - If the file cannot be found or the path refers to a directory.

RMIException - If the call cannot be completed due to a network error.

read

public byte[] read(Path file,
                   long offset,
                   int length)
            throws java.io.FileNotFoundException,
                   java.io.IOException,
                   RMIException

Description copied from interface: Storage

Reads a sequence of bytes from a file.

Specified by:

read in interface Storage

Parameters:

file - Path to the file.

offset - Offset into the file to the beginning of the sequence.

length - The number of bytes to be read.

Returns:

An array containing the bytes read. If the call succeeds, the number of bytes read is equal to the number of bytes requested.

Throws:

java.io.FileNotFoundException - If the file cannot be found or the path refers to a directory.

java.io.IOException - If the file read cannot be completed on the server.

RMIException - If the call cannot be completed due to a network error.

write

public void write(Path file,
                  long offset,
                  byte[] data)
           throws java.io.FileNotFoundException,
                  java.io.IOException

Description copied from interface: Storage

Writes bytes to a file.

Specified by:

write in interface Storage

Parameters:

file - Path to the file.

offset - Offset into the file where data is to be written.

data - Array of bytes to be written.

Throws:

java.io.FileNotFoundException - If the file cannot be found or the path refers to a directory.

java.io.IOException - If the file write cannot be completed on the server.

create

public boolean create(Path file)

Description copied from interface: Command

Creates a file on the storage server.

Specified by:

create in interface Command

Parameters:

file - Path to the file to be created. The parent directory will be created if it does not exist. This path may not be the root directory.

Returns:

true if the file is created; false if it cannot be created.

deleteHelper

private java.lang.Boolean deleteHelper(java.io.File f)

delete

public boolean delete(Path path)

Description copied from interface: Command

Deletes a file or directory on the storage server.

If the file is a directory and cannot be deleted, some, all, or none of its contents may be deleted by this operation.

Specified by:

delete in interface Command

Parameters:

path - Path to the file or directory to be deleted. The root directory cannot be deleted.

Returns:

true if the file or directory is deleted; false otherwise.

copy

public boolean copy(Path file,
                    Storage server)
             throws RMIException,
                    java.io.FileNotFoundException,
                    java.io.IOException

Description copied from interface: Command

Copies a file from another storage server.

Specified by:

copy in interface Command

Parameters:

file - Path to the file to be copied.

server - Storage server from which the file is to be downloaded.

Returns:

true if the file is successfully copied; false otherwise.

Throws:

RMIException - If the call cannot be completed due to a network error, whether between the caller and this storage server, or between the two storage servers.

java.io.FileNotFoundException - If the file is not present on the remote storage server, or the path refers to a directory.

java.io.IOException - If an I/O exception occurs either on the remote or on this storage server.