org.lsst.ccs.framework

Class CommandPresenceAgent

java.lang.Object

org.lsst.ccs.framework.CommandPresenceAgent

All Implemented Interfaces:

BusMembershipListener, StatusListener, StatusListens

public class CommandPresenceAgent
extends Object
implements StatusListener, BusMembershipListener

Instance of this class are to be used by codes such as BusMasters to monitor the presence of subsystem on the Command bus. The code is based upon a broadcast message PingCommand that is sent to all subsystems. Then by listening to the status bus the code is aware of responses to this "ping" and of StatusForEnd, StatusForStart messages. Due to the asynchronous nature of messages and to the fact that a Subsystem may die before sending a StatusForEnd message, uses of this code may be complemented by calls to the communication layer BusApplicationLayer.connectedToCommand() method and/or to the reset() method in this class.

Author:

bamade

Constructor Summary

Constructors

Constructor and Description
CommandPresenceAgent(MessagingFactory fac) creates such an agent that operates on the given bus access.

Method Summary

Modifier and Type	Method and Description
void	anormalEvent(Exception exc) notification of an incident (sending a message to a non-existing agent and so on)
void	connecting(String agentName, String otherInfos) a new agent is connected to the bus
void	disconnecting(String agentName, String otherInfos) if the communication layer notifies us of a disconnection then the corresponding agent is removed from the map.
List<String>	list(boolean masters, boolean slaves) Returns the names of the subsystems that are presently connected to the COMMAND bus.
List<String>	listAll() return the name of all subsystems that are known to be connected to the command bus.
List<String>	listMasters()
List<String>	listSlaves()
void	onStatus(BusMessage s) updates to the subsystem map with status messages: responses to "ping" requests birth or death notifications
void	reset() try to reinitialize the map of known subsystems.

Methods inherited from class java.lang.Object

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

Constructor Detail

CommandPresenceAgent

public CommandPresenceAgent(MessagingFactory fac)

creates such an agent that operates on the given bus access.

Parameters:

fac -

Method Detail

onStatus

public void onStatus(BusMessage s)

updates to the subsystem map with status messages:

• responses to "ping" requests
• birth or death notifications

Specified by:

onStatus in interface StatusListener

Parameters:

s -

connecting

public void connecting(String agentName,
                       String otherInfos)

Description copied from interface: BusMembershipListener

a new agent is connected to the bus

Specified by:

connecting in interface BusMembershipListener

otherInfos - free form string to add comments to the event

disconnecting

public void disconnecting(String agentName,
                          String otherInfos)

if the communication layer notifies us of a disconnection then the corresponding agent is removed from the map.

Specified by:

disconnecting in interface BusMembershipListener

Parameters:

agentName -

otherInfos -

anormalEvent

public void anormalEvent(Exception exc)

Description copied from interface: BusMembershipListener

notification of an incident (sending a message to a non-existing agent and so on)

Specified by:

anormalEvent in interface BusMembershipListener

reset

public void reset()

try to reinitialize the map of known subsystems.

list

public List<String> list(boolean masters,
                         boolean slaves)

Returns the names of the subsystems that are presently connected to the COMMAND bus. The names are filtered according to the "slave" and "master" features of the subsystems: "master" meaning that the subsystem is a BusMaster, "slave" that it is passive (Modular subsystems executing commands). Note that some subsystems can be both (MCM) or none of these (Databases, Tracers).

Parameters:

masters -

slaves -

Returns:

listMasters

public List<String> listMasters()

Returns:

the list of known subsystems that are masters.

listSlaves

public List<String> listSlaves()

Returns:

the list of subsystems that are slaves.

listAll

public List<String> listAll()

return the name of all subsystems that are known to be connected to the command bus.

Returns: