de.fhg.igd.atlas.core
Class AgentTracerImpl

java.lang.Object
  de.fhg.igd.semoa.service.AbstractService
      de.fhg.igd.atlas.core.AgentTracerImpl

All Implemented Interfaces:

AgentTracer, Runnable, Service

public class AgentTracerImpl

extends AbstractService

implements AgentTracer, Runnable

Provides the function of an Agent Tracer, which tracks the current location of agents, making use of a locally installed LSClientService interface. Agents can be added and removed to a watch list. In certain update intervals the update daemon initiates lookups to resolve the current contact addresses of all agents in the watch list. The corresponding (implicit name, contact address) correlations can be requested as SortedMap.

Version:

"$Id: AgentTracerImpl.java 1913 2007-08-08 02:41:53Z jpeters $"

Author:

Jan Peters

See Also:

LSClientService, AgentTracerGui

Field Summary

protected LSClientService	clientService_ The reference to a locally installed LSClientService which is used to lookup the agent's contact addresses.
private Object	datalock_ The internal lock object used for synchronisation of watchList respectively tracedAgents_ modifications.
private static String[]	DEPEND_ The dependencies to other objects in the global Environment.
protected EventReflector	eventReflector_ The event reflector which is notified, every time a refresh request has been executed successfully.
private Object	lock_ The internal lock object used for the tracerThread_.
int	LOOKUP_ATTEMPTS The number of allowed unsuccessful lookups for an agent contact address, before the agent will be removed from the watch list.
protected Signals	signals_ Used for for signaling between database and tracerThread.
protected SortedMap	tracedAgents_ The current contact addresses of all agents in the watch list are stored in this map.
protected Thread	tracerThread_ Thread that provides the functionality of the update daemon.
protected long	updateTime_ Update time for the update daemon.
protected SortedMap	watchList_ Represents the watch list, which stores the implicit names of the agents and the number of unsuccessful lookups.

Fields inherited from class de.fhg.igd.semoa.service.AbstractService

REV_POSTFIX, REV_PREFIX

Fields inherited from interface de.fhg.igd.atlas.core.AgentTracer

WHATIS

Constructor Summary

AgentTracerImpl()
Creates a new instance of the agent tracer with the a update time of 1000ms for its update daemon.

AgentTracerImpl(long updateTime)
Creates a new instance of the agent tracer with the given updateTime for its update daemon.

Method Summary

void	addAgentToWatchList(AgentCard card) Adds an agent to the agent tracer's watch list.
void	addAgentToWatchList(byte[] implicitName) Adds an agent to the agent tracer's watch list.
TrustedListener	addListener(Listener listener) Adds a Listener.
String	author() Returns the String with the author's name.
String[]	dependencies() Returns the dependencies of this service as described in Service.
long	getUpdateTime() Returns the update interval of the agent tracer.
String	info() Returns the String with the service's short description.
SortedMap	list() Returns a copy of the internally used map which holds the (implicit name, contact address) correlations of the last update.
String	printTracedAgents() Returns the string representation of the stored (implicit name, contact address) correlations.
void	refresh() Initiates a contact address update for all agents in the agent tracer's watch list.
void	removeAgentFromWatchList(AgentCard card) Removes an agent from the agent tracer's watch list.
void	removeAgentFromWatchList(byte[] implicitName) Removes an agent from the agent tracer's watch list.
String	revision() Returns the revision number of this class as a string.
void	run() This method represents the functionality of the update daemon.
void	setUpdateTime(long updateTime) Sets the update interval of the agent tracer.
private void	stop() Stops the tracerThread_.
String	toString()

Methods inherited from class de.fhg.igd.semoa.service.AbstractService

checkDependencies, docs, doPrivileged, doPrivileged, getACC, getEnvironment, majorVersion, minorVersion

Methods inherited from class java.lang.Object

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

Field Detail

DEPEND_

private static final String[] DEPEND_

The dependencies to other objects in the global Environment.

LOOKUP_ATTEMPTS

public final int LOOKUP_ATTEMPTS

The number of allowed unsuccessful lookups for an agent contact address, before the agent will be removed from the watch list.

See Also:

Constant Field Values

clientService_

protected LSClientService clientService_

The reference to a locally installed LSClientService which is used to lookup the agent's contact addresses.

eventReflector_

protected EventReflector eventReflector_

The event reflector which is notified, every time a refresh request has been executed successfully.

updateTime_

protected long updateTime_

Update time for the update daemon.

watchList_

protected SortedMap watchList_

Represents the watch list, which stores the implicit names of the agents and the number of unsuccessful lookups.

tracedAgents_

protected SortedMap tracedAgents_

The current contact addresses of all agents in the watch list are stored in this map. They are sorted over the corresponding implicit names.

tracerThread_

protected Thread tracerThread_

Thread that provides the functionality of the update daemon.

signals_

protected Signals signals_

Used for for signaling between database and tracerThread.

lock_

private Object lock_

The internal lock object used for the tracerThread_.

datalock_

private Object datalock_

The internal lock object used for synchronisation of watchList respectively tracedAgents_ modifications.

Constructor Detail

AgentTracerImpl

public AgentTracerImpl()

Creates a new instance of the agent tracer with the a update time of 1000ms for its update daemon.

AgentTracerImpl

public AgentTracerImpl(long updateTime)

Creates a new instance of the agent tracer with the given updateTime for its update daemon.

Parameters:

updateTime - The update time in milli seconds.

Method Detail

info

public String info()

Returns the String with the service's short description.

Specified by:

info in interface Service

Specified by:

info in class AbstractService

Returns:

The String with the service's short description.

author

public String author()

Returns the String with the author's name.

Specified by:

author in interface Service

Specified by:

author in class AbstractService

Returns:

The String with the author's name.

revision

public String revision()

Returns the revision number of this class as a string.

Specified by:

revision in class AbstractService

Returns:

The revision number of this class as a string.

dependencies

public String[] dependencies()

Returns the dependencies of this service as described in Service.

Specified by:

dependencies in interface Service

Overrides:

dependencies in class AbstractService

Returns:

The array of dependencies.

toString

public String toString()

Overrides:

toString in class AbstractService

Returns:

The string representation of this instance.

addAgentToWatchList

public void addAgentToWatchList(AgentCard card)

Adds an agent to the agent tracer's watch list. The agent identified by the given agentCard will be registered within the agent tracer and lookups will be initiated in certain update intervals to resolve its current contact address. If the contact address of an agent in the watch list could not be resolved for a certain number of update cycles, it is automatically removed from the list, again. Theadded to the watch list if not already

Specified by:

addAgentToWatchList in interface AgentTracer

Parameters:

card - The agent card of the agent.

addAgentToWatchList

public void addAgentToWatchList(byte[] implicitName)

Adds an agent to the agent tracer's watch list. The agent identified by the given implicitName will be registered within the agent tracer and lookups will be initiated in certain update intervals to resolve its current contact address. If the contact address of an agent in the watch list could not be resolved for a certain number of update cycles, it is automatically removed from the list, again. Theadded to the watch list if not already

Specified by:

addAgentToWatchList in interface AgentTracer

removeAgentFromWatchList

public void removeAgentFromWatchList(AgentCard card)

Removes an agent from the agent tracer's watch list. If the agent identified by the given agentCard can be found in the watch list, it is removed immediately.

Specified by:

removeAgentFromWatchList in interface AgentTracer

removeAgentFromWatchList

public void removeAgentFromWatchList(byte[] implicitName)

Removes an agent from the agent tracer's watch list. If the agent identified by the given implicitName can be found in the watch list, it is removed immediately.

Specified by:

removeAgentFromWatchList in interface AgentTracer

Parameters:

implicitName - The implicit name of the agent.

addListener

public TrustedListener addListener(Listener listener)

Adds a Listener. The Listener will receive events of the type String every time an update has been initiated by the agent tracer's update daemon respectively by a call of refresh. Listener instances passed to this method shall be wrapped in a TrustedListener which is then returned.

Specified by:

addListener in interface AgentTracer

Parameters:

listener - The Listener to be registered.

Returns:

The TrustedListener that wraps around the given Listener.

Throws:

NullPointerException - if listener is null.

list

public SortedMap list()

Returns a copy of the internally used map which holds the (implicit name, contact address) correlations of the last update. The entries of the type Map.Entry consist of the implicit name of the agent (byte[]) as key and the contact address (URL) as corresponding value. If the contact address of an agent could not be resolved the nth time, a URL of following format is returned:

error://unknown/n

Specified by:

list in interface AgentTracer

Returns:

The sorted map of (implicit name, contact address) correlations.

refresh

public void refresh()

Initiates a contact address update for all agents in the agent tracer's watch list. This method can be used to refresh the (implicit name, contact address) correlations, even if the update mechanism is deactivated.

Specified by:

refresh in interface AgentTracer

getUpdateTime

public long getUpdateTime()

Returns the update interval of the agent tracer.

Specified by:

getUpdateTime in interface AgentTracer

Returns:

The update time of the agent tracer or 0 if the update mechanism is deactivated.

setUpdateTime

public void setUpdateTime(long updateTime)

Sets the update interval of the agent tracer. The given value determines the interval in which the agent tracer updates the contact addresses of the agents in its watch list. An updateTime of 0 deactivates the update mechanism.

Specified by:

setUpdateTime in interface AgentTracer

run

public void run()

This method represents the functionality of the update daemon.

Specified by:

run in interface Runnable

stop

private void stop()

Stops the tracerThread_.

printTracedAgents

public String printTracedAgents()

Returns the string representation of the stored (implicit name, contact address) correlations.

Returns:

The string representation.