examples.communication
Class Agent

java.lang.Object
  examples.communication.Agent

All Implemented Interfaces:

AgentService, Resumable, Runnable, Serializable

public class Agent

extends Object

implements Resumable, Serializable, AgentService

This class represents three types of agents which jump subseqeuently to remote hosts, and communicate with each other:

SENDER - the sender agent only sends messages

RECEWIVER - the receiver agent only receives messages

TRANSCEIVER - the transceiver agent sends and receives messages

Every agent publishes its own AgentService which makes possible for the Launcher to send this agent the implicit names of all other "friend" agents or to signal for termination when an error occurs.

The agent (no matter what type) goes through the following states:

STATE_INIT_VARIABLES: in this state the agent initialises the varibles, set from the Launcher, its implicit name, etc..

STATE_REPORT_FEEDBACK: the agent reports to the Launcher errors(if they have occurred) and its implict name, nickname, the key of the service it has published and its type.

STATE_COMMUNICATE: if the agent is from type SENDER or TRANSCEIVER it tries to send message to one of the RECEIVER agents; if the agent is from type RECEIVER it checks constantly for a new message in the time between each migration.

STATE_TERMINATE: the agent terminates because of error or it has gone through its "lifecycle". Before the termination each agent should "report" the information about how many messages it has received/ sent and how many of them have benn received/not received.

This class implements the interface Resumable. This means if there was an error, which appeared during the program execution, and the agent is not in STATE_TERMINATE, it will try to migrate to the host where it was first launched and report the information it has gathered.

Author:

Zaharina Velikova, Jan Peters

See Also:

Serialized Form

Field Summary

static String	COMM_TYPE_PROP String representation of TYPE property in agent's properties.
static String	COMM_TYPE_RECEIVER String representation of the agent's type RECEIVER.
static String	COMM_TYPE_SENDER String representation of the agent's type SENDER.
static String	COMM_TYPE_TRANSCEIVER String representation of the agent's type TRANSCEIVER.
static int	CT_RECEIVER int representation of the agent's type RECEIVER.
static int	CT_SENDER int representation of the agent's type SENDER.
static int	CT_TRANSCEIVER int representation of the agent's type TRANSCEIVER.
private URL	home_ The de.fhg.igd.util.URL of the "home" of the agent(where the agent was first started).
private String	id_ The id of the agent used for log messages.
private String	implicitName_ The implicit name of the agent.
private ArrayList	implicitNames_ The list with the names of the "receiver" agents.
static String	JUMP_COUNT_PROP String representation of the property "count of jumps".
private int	jumpCount_ Current number of successfull jumps..
private int	jumps_ The number of times which the agent must migrate.
private Object	lock_ Lock object for internal synchronization.
private int	messagesNotDelivered_ The number of the messages which were not delivered.
private int	messagesReceived_ The number of the received messages.
private int	messagesSent_ The number of the sent messages.
private String	nickName_ The nickname of the agent.
static String	NICKNAME_PREFIX This is the prefix of each agent's nickname.
private HashMap	notDeliveredNotices_ The HashMap object which contains the messages from the exceptions of not delivered messages.
private static long	serialVersionUID Use serialVersionUID for interoperability.
static String	SERVER_PREFIX_PROP String representation of the prefix of all urls in the agent's properties.
private int	state_ The state of the agent.
static int	STATE_COMMUNICATE Represents the third(main) state of the agent's lifecycle.
static int	STATE_INIT_VARIABLES Represents the first state of the agent's lifecycle.
static int	STATE_REPORT_FEEDBACK Represents the second state of the agent's lifecycle.
static int	STATE_TERMINATE Represents the last state(termination) of the agent's lifecycle.
private ArrayList	targets_ The ArrayList with the urls where the agent can migrate.
private boolean	terminate_ The state of the agent.
private long	time_ The time(in milliseconds) which the agent has before each migration.
private int	type_ The type of this agent.
static String	WAIT_TIME_PROP String representation of the "waiting time before each migration" property.

Fields inherited from interface examples.communication.AgentService

PUBLISH_KEY_PREFIX

Constructor Summary

Agent()
Default constructor.

Method Summary

protected ArrayList	findValidTargets() Initializes the URL array from the Vicinity service.
protected URL	getLocalHost() Resolves the localhost url.
protected URL	getNextTarget() Finds a random reachable target for the next agent's migration.
void	initImplicitNames(ArrayList implicitNames) Initialises the implicit name of the agent's "friends"
protected void	migrate() Sets the Ticket according to the random choice of examples.communication.Agent#getNextTarget().
protected void	migrateHome() Sets the next migration target the host whrere the agent was first started.
void	resume(ErrorCode error) See class description.
void	run() See class description.
void	signalTermination() Sends a terminating signal to the agent.
protected boolean	stateCommunicate() Describes the state: STATE_COMMUNICATE.
protected boolean	stateInitVariables() Describes the state: STATE_INIT_VARIABLES.
protected boolean	stateReportFeedback() Describes the state: STATE_REPORT_FEEDBACK.
protected void	terminate() The agent reports the information about how many messages it has received/sent and how many of them have been received/not received and terminates.

Methods inherited from class java.lang.Object

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

Field Detail

serialVersionUID

private static final long serialVersionUID

Use serialVersionUID for interoperability.

See Also:

Constant Field Values

STATE_INIT_VARIABLES

public static final int STATE_INIT_VARIABLES

Represents the first state of the agent's lifecycle.

See Also:

description, Constant Field Values

STATE_REPORT_FEEDBACK

public static final int STATE_REPORT_FEEDBACK

Represents the second state of the agent's lifecycle.

See Also:

description, Constant Field Values

STATE_COMMUNICATE

public static final int STATE_COMMUNICATE

Represents the third(main) state of the agent's lifecycle.

See Also:

description, Constant Field Values

STATE_TERMINATE

public static final int STATE_TERMINATE

Represents the last state(termination) of the agent's lifecycle.

See Also:

description, Constant Field Values

NICKNAME_PREFIX

public static final String NICKNAME_PREFIX

This is the prefix of each agent's nickname. If there were no errors during launching an agent, it should get a nickname of type: "Agent-index:type" where index is the index under which it was launched by the Launcher and "type" is a string representation of the agent's type.

See Also:

Constant Field Values

CT_SENDER

public static final int CT_SENDER

int representation of the agent's type SENDER.

See Also:

Constant Field Values

CT_RECEIVER

public static final int CT_RECEIVER

int representation of the agent's type RECEIVER.

See Also:

Constant Field Values

CT_TRANSCEIVER

public static final int CT_TRANSCEIVER

int representation of the agent's type TRANSCEIVER.

See Also:

Constant Field Values

COMM_TYPE_SENDER

public static final String COMM_TYPE_SENDER

String representation of the agent's type SENDER.

See Also:

Constant Field Values

COMM_TYPE_RECEIVER

public static final String COMM_TYPE_RECEIVER

String representation of the agent's type RECEIVER.

See Also:

Constant Field Values

COMM_TYPE_TRANSCEIVER

public static final String COMM_TYPE_TRANSCEIVER

String representation of the agent's type TRANSCEIVER.

See Also:

Constant Field Values

COMM_TYPE_PROP

public static final String COMM_TYPE_PROP

String representation of TYPE property in agent's properties.

See Also:

Constant Field Values

SERVER_PREFIX_PROP

public static final String SERVER_PREFIX_PROP

String representation of the prefix of all urls in the agent's properties.

See Also:

Constant Field Values

WAIT_TIME_PROP

public static final String WAIT_TIME_PROP

String representation of the "waiting time before each migration" property.

See Also:

Constant Field Values

JUMP_COUNT_PROP

public static final String JUMP_COUNT_PROP

String representation of the property "count of jumps".

See Also:

Constant Field Values

implicitNames_

private ArrayList implicitNames_

The list with the names of the "receiver" agents.

targets_

private ArrayList targets_

The ArrayList with the urls where the agent can migrate.

notDeliveredNotices_

private HashMap notDeliveredNotices_

The HashMap object which contains the messages from the exceptions of not delivered messages.

nickName_

private String nickName_

The nickname of the agent.

implicitName_

private String implicitName_

The implicit name of the agent.

time_

private long time_

The time(in milliseconds) which the agent has before each migration.

jumps_

private int jumps_

The number of times which the agent must migrate. This number will be considered only if the targets for migration of the agent are more than 1.

home_

private URL home_

The de.fhg.igd.util.URL of the "home" of the agent(where the agent was first started).

type_

private int type_

The type of this agent.

See Also:

description

jumpCount_

private int jumpCount_

Current number of successfull jumps..

id_

private String id_

The id of the agent used for log messages.

lock_

private transient Object lock_

Lock object for internal synchronization.

messagesNotDelivered_

private int messagesNotDelivered_

The number of the messages which were not delivered.

messagesReceived_

private int messagesReceived_

The number of the received messages.

messagesSent_

private int messagesSent_

The number of the sent messages.

state_

private int state_

The state of the agent.

terminate_

private boolean terminate_

The state of the agent.

Constructor Detail

Agent

public Agent()

Default constructor.

Method Detail

getLocalHost

protected URL getLocalHost()

Resolves the localhost url.

Returns:

the url of the local host or null if the localhost cannot be found.

findValidTargets

protected ArrayList findValidTargets()

Initializes the URL array from the Vicinity service.

Returns:

The ArrayList of found targets or null, if Vicinity is not installed.

getNextTarget

protected URL getNextTarget()

Finds a random reachable target for the next agent's migration.

Returns:

A reachable url.

resume

public void resume(ErrorCode error)
            throws Exception

See class description.

Specified by:

resume in interface Resumable

Parameters:

error - DOCUMENT ME!

Throws:

Exception - DOCUMENT ME!

run

public void run()

See class description.

Specified by:

run in interface Runnable

migrate

protected void migrate()

Sets the Ticket according to the random choice of examples.communication.Agent#getNextTarget(). If no valid destination was found the agent terminates.

See Also:

terminate()

migrateHome

protected void migrateHome()

Sets the next migration target the host whrere the agent was first started.

terminate

protected void terminate()

The agent reports the information about how many messages it has received/sent and how many of them have been received/not received and terminates.

stateInitVariables

protected boolean stateInitVariables()

Describes the state: STATE_INIT_VARIABLES. See class description.

Returns:

DOCUMENT ME!

stateReportFeedback

protected boolean stateReportFeedback()

Describes the state: STATE_REPORT_FEEDBACK. See class description.

Returns:

DOCUMENT ME!

stateCommunicate

protected boolean stateCommunicate()

Describes the state: STATE_COMMUNICATE. See class description.

Returns:

DOCUMENT ME!

initImplicitNames

public void initImplicitNames(ArrayList implicitNames)

Description copied from interface: AgentService

Initialises the implicit name of the agent's "friends"

Specified by:

initImplicitNames in interface AgentService

Parameters:

implicitNames - DOCUMENT ME!

See Also:

AgentService.initImplicitNames(ArrayList)

signalTermination

public void signalTermination()

Description copied from interface: AgentService

Sends a terminating signal to the agent.

Specified by:

signalTermination in interface AgentService

See Also:

AgentService.signalTermination()