ParkNPark.client
Class FaultTolerantClientManager

java.lang.Object
  ParkNPark.client.FaultTolerantClientManager

All Implemented Interfaces:

ClientManagerOperations

public class FaultTolerantClientManager
extends Object
implements ClientManagerOperations

Fault tolerant client manager that wraps a remote ClientManager and rolls over to a new primary server in the presence of failures. Note that this class is not multi-thread safe. Multiple threads should synchronize access or wrap this class with a thread-safe delegate.

Nested Class Summary

protected class

FaultTolerantClientManager.ReturnValueOrException Return value or an exception along with the return value or the exception object.

Field Summary

protected int	clientID The server-generated client ID
protected static Method	closeClientManager
protected static Method	enterLot
protected static Method	exitLot
protected static Method	getClientID
protected static Method	getCurrentLevel
protected static Method	getLots
protected static Method	getMaxLevel
protected static Method	getMinLevel
protected static Method	getOtherLotAvailability
protected static PrintStream	inputEater Shared static instance of the input eater output stream wrapped in a PrintStream
protected static Method	moveDownLevel
protected static Method	moveUpLevel
protected NamingContextExt	nameServer Our name server instance
protected ORB	orb Our object request broker
protected NamingContext	parkNParkContext Our naming service's ParkNPark context, which contains server registrations
protected ClientManager	primaryClientManager The primary client manager
protected int	seq The latest sequence number from the client
protected static String	unexpectedException Message for unexpected exceptions that arise during remote method calls (non-IDL and non-CORBA exceptions)

Constructor Summary

FaultTolerantClientManager(ORB orb)
Creates a new fault-tolerant client manager that automatically fails over to new primary servers on method call failures

Method Summary

protected FaultTolerantClientManager.ReturnValueOrException	callServer(Method method, Object... arguments) Calls the given method on the server with the given arguments and returns a ReturnValueOrException object to indicate a normal or exceptional result and contain the return value or the exception object.
void	closeClientManager() Closes the client manager and frees server resources associated with it, including the client manager's activation in the server's CORBA portable object adapter
int[]	enterLot(int seq, int lot) Moves the client's car into the lot with the given lot number and returns an array of level numbers that have available spaces
void	exitLot(int seq) Removes the client's car from the lot that it is currently in
int	getClientID() Returns the client's ID, which can be used in the client manager factory's getExistingClientManager() method
int	getCurrentLevel() Returns the car's current level number
int[]	getLots() Returns an array of valid lot numbers in the system, sorted by the lot number in ascending order
int	getMaxLevel() Returns the top level number of the car's current parking lot
int	getMinLevel() Returns the bottom level number of the car's current parking lot
int[]	getOtherLotAvailability(int lot) Returns an array of other lots that have availability, sorted by lot distance such that closer lots are listed first
protected boolean	getPrimaryServer() Refreshes the primary server that is registered in the name service
int	moveDownLevel(int seq) Moves the car from its present level to the level beneath it
int	moveUpLevel(int seq) Moves the car from its present level to the level above it
protected boolean	refreshParkNParkContext() Refreshes the parkNParkContext name service object that we use to get server bindings on.

Methods inherited from class java.lang.Object

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

Field Detail

parkNParkContext

protected NamingContext parkNParkContext

Our naming service's ParkNPark context, which contains server registrations

primaryClientManager

protected ClientManager primaryClientManager

The primary client manager

nameServer

protected NamingContextExt nameServer

Our name server instance

seq

protected int seq

The latest sequence number from the client

clientID

protected int clientID

The server-generated client ID

orb

protected ORB orb

Our object request broker

getClientID

protected static final Method getClientID

enterLot

protected static final Method enterLot

exitLot

protected static final Method exitLot

getOtherLotAvailability

protected static final Method getOtherLotAvailability

getLots

protected static final Method getLots

moveUpLevel

protected static final Method moveUpLevel

moveDownLevel

protected static final Method moveDownLevel

getCurrentLevel

protected static final Method getCurrentLevel

getMaxLevel

protected static final Method getMaxLevel

getMinLevel

protected static final Method getMinLevel

closeClientManager

protected static final Method closeClientManager

unexpectedException

protected static final String unexpectedException

Message for unexpected exceptions that arise during remote method calls (non-IDL and non-CORBA exceptions)

See Also:

Constant Field Values

inputEater

protected static PrintStream inputEater

Shared static instance of the input eater output stream wrapped in a PrintStream

Constructor Detail

FaultTolerantClientManager

public FaultTolerantClientManager(ORB orb)
                           throws ServiceUnavailableException

Creates a new fault-tolerant client manager that automatically fails over to new primary servers on method call failures

Parameters:

orb - The object request broker instance to use

Throws:

ServiceUnavailableException - Thrown when a primary server could not be located or contacted

Method Detail

callServer

protected FaultTolerantClientManager.ReturnValueOrException callServer(Method method,
                                                                       Object... arguments)

Calls the given method on the server with the given arguments and returns a ReturnValueOrException object to indicate a normal or exceptional result and contain the return value or the exception object. If server communication or service unavailability exceptions arise, this method will automatically fail over to the new primary after that becomes available. Server communication and service unavailability exceptions are only returned if no primary server is registered

Parameters:

method - The method to call on our client manager on the primary server

arguments - The arguments to pass to the given method's parameters

Returns:

A ReturnValueOrException indicating a normal or exceptional result

getPrimaryServer

protected boolean getPrimaryServer()

Refreshes the primary server that is registered in the name service

Returns:

True if the primary server reference is refreshed or false if it could not be refreshed

refreshParkNParkContext

protected boolean refreshParkNParkContext()

Refreshes the parkNParkContext name service object that we use to get server bindings on. The name service is contacted from scratch in this method

Returns:

True if the parkNParkContext was refreshed or false if it was not

getClientID

public int getClientID()

Returns the client's ID, which can be used in the client manager factory's getExistingClientManager() method

Specified by:

getClientID in interface ClientManagerOperations

Returns:

The client's ID

enterLot

public int[] enterLot(int seq,
                      int lot)
               throws AlreadyInLotException,
                      LotNotFoundException,
                      LotFullException,
                      ServiceUnavailableException

Moves the client's car into the lot with the given lot number and returns an array of level numbers that have available spaces

Specified by:

enterLot in interface ClientManagerOperations

Parameters:

seq - The latest sequence number of the client

lot - The lot number to enter

Returns:

An array of level numbers that have available spaces [Category: Baseline; Requirements: 1, 2, and 3]

Throws:

AlreadyInLotException - Thrown when the client's car is already in a lot

LotNotFoundException - Thrown if the given lot number is not known to the system

LotFullException - Thrown if the given lot is full

ServiceUnavailableException - Thrown if the database cannot be contacted or if some other reason prevents the car from entering the lot

exitLot

public void exitLot(int seq)
             throws NotInLotException,
                    NotOnExitLevelException,
                    ServiceUnavailableException

Removes the client's car from the lot that it is currently in

Specified by:

exitLot in interface ClientManagerOperations

Parameters:

seq - The latest sequence number of the client

Throws:

NotInLotException - Thrown if the car is not in a lot

NotOnExitLevelException - Thrown if the car is in a lot but is not on a permitted exit level

ServiceUnavailableException - Thrown if the database cannot be contacted or if some other reason prevents the car from exiting the lot [Category: Baseline; Requirement: 7]

getOtherLotAvailability

public int[] getOtherLotAvailability(int lot)
                              throws LotNotFoundException,
                                     ServiceUnavailableException

Returns an array of other lots that have availability, sorted by lot distance such that closer lots are listed first

Specified by:

getOtherLotAvailability in interface ClientManagerOperations

Parameters:

lot - The lot to get lot distances from

Returns:

An array of other lots that have availability [Category: Baseline; Requirement: 4]

Throws:

LotNotFoundException - Thrown if the given lot number is not known to the system

ServiceUnavailableException - Thrown if the database cannot be contacted or if some other reason prevents the system from discovering the availability of other lots

getLots

public int[] getLots()
              throws ServiceUnavailableException

Returns an array of valid lot numbers in the system, sorted by the lot number in ascending order

Specified by:

getLots in interface ClientManagerOperations

Returns:

An array of valid lot numbers in the system [Category: Baseline; Requirement: 12]

Throws:

ServiceUnavailableException - Thrown if the database cannot be contacted or if some other reason prevents the system from discovering the its defined lots

moveUpLevel

public int moveUpLevel(int seq)
                throws NotInLotException,
                       AtTopLevelException,
                       ServiceUnavailableException

Moves the car from its present level to the level above it

Specified by:

moveUpLevel in interface ClientManagerOperations

Parameters:

seq - The latest sequence number of the client

Returns:

The level number that the client's car is now on [Category: Baseline; Requirement: 6]

Throws:

NotInLotException - Thrown if the car is not in a lot

AtTopLevelException - Thrown if the car is already on the highest level

ServiceUnavailableException - Thrown if the database cannot be contacted or if some other reason prevents the car from moving to the next highest level

moveDownLevel

public int moveDownLevel(int seq)
                  throws NotInLotException,
                         AtBottomLevelException,
                         ServiceUnavailableException

Moves the car from its present level to the level beneath it

Specified by:

moveDownLevel in interface ClientManagerOperations

Parameters:

seq - The latest sequence number of the client

Returns:

The level number that the client's car is now on [Category: Baseline; Requirement: 6]

Throws:

NotInLotException - Thrown if the car is not in a lot

AtTopLevelException - Thrown if the car is already on the lowest level

ServiceUnavailableException - Thrown if the database cannot be contacted or if some other reason prevents the car from moving to the lower level

AtBottomLevelException

getCurrentLevel

public int getCurrentLevel()
                    throws NotInLotException,
                           ServiceUnavailableException

Returns the car's current level number

Specified by:

getCurrentLevel in interface ClientManagerOperations

Returns:

The car's current level number [Category: Baseline; Requirement: 6]

Throws:

NotInLotException - Thrown if the car is not in a lot

ServiceUnavailableException - Thrown if the database cannot be contacted or if some other reason prevents the system from returning the car's current level

getMaxLevel

public int getMaxLevel()
                throws NotInLotException,
                       ServiceUnavailableException

Returns the top level number of the car's current parking lot

Specified by:

getMaxLevel in interface ClientManagerOperations

Returns:

The top level number of the car's current parking lot [Category: Baseline; Requirement: 6]

Throws:

NotInLotException - Thrown if the car is not in a lot

ServiceUnavailableException - Thrown if the database cannot be contacted or if some other reason prevents the system from returning the current lot's highest level

getMinLevel

public int getMinLevel()
                throws NotInLotException,
                       ServiceUnavailableException

Returns the bottom level number of the car's current parking lot

Specified by:

getMinLevel in interface ClientManagerOperations

Returns:

The bottom level number of the car's current parking lot [Category: Baseline; Requirement: 6]

Throws:

NotInLotException - Thrown if the car is not in a lot

ServiceUnavailableException - Thrown if the database cannot be contacted or if some other reason prevents the system from returning the current lot's lowest level

closeClientManager

public void closeClientManager()
                        throws ServiceUnavailableException

Closes the client manager and frees server resources associated with it, including the client manager's activation in the server's CORBA portable object adapter

Specified by:

closeClientManager in interface ClientManagerOperations

Throws:

ServiceUnavailableException - Thrown if the database cannot be contacted or if some other reason prevents the system from closing the client manager. The client manager remains open if this exception gets thrown