org.lsst.ccs.messaging.jgroups

Class JGroupsBusMessagingLayer

java.lang.Object

org.lsst.ccs.messaging.jgroups.JGroupsBusMessagingLayer

All Implemented Interfaces:

Closeable, AutoCloseable, BusMessagingLayer, MessagingLayer, ProvidesDisconnectionInformation

public class JGroupsBusMessagingLayer
extends Object
implements BusMessagingLayer, ProvidesDisconnectionInformation

Each Bus is represented by a JGroups cluster.

Each agent creates a JChannel, setName to name of agent and connect to corresponding Bus/cluster (so each agent may have up to 3 JChannel connected).
Each of these 3 channels have a JGroups Address.

for sending messages to an agent we have to find its Address in the group AND we have to find the addresses of the multiple anonymous agents that will receive a copy

There is a dictionary to match agent name to jGroups Address. for each agent there is an Address except for anonymous agent that can be matched to multiple addresses.

< * p/> ImPortant every Jchannel in the JVM MUST be closed!

Field Summary

Fields

Modifier and Type	Field and Description
static String	DEFAULT_UDP_PROTOCOL

Method Summary

Modifier and Type	Method and Description
void	addMessageListener(String agentName, BusMessageForwarder forwarder, Bus... buses) Sets up callback configuration for a topic and subsystem.
void	close() Close the Transport Layer.
void	closeFor(String agentName, Bus... buses) close entry points for a bus for an agent.
void	connect(MessagingAccessLayer accessLayer) Connects a MessagingAccessLayer object on the buses by using its name as a unique identifier.
void	disconnect(MessagingAccessLayer accessLayers) Remove the entry point to the buses for the given MessagingAccessLayer.
Set<String>	getRegisteredLocalAgents(Bus... buses) Get the list of local agents currently connected to the buses.
void	register(String agentName, Bus... buses) Creates low level communication entry points for a subsystem.
void	removeMessageListener(String agentName, BusMessageForwarder forwarder, Bus... buses) Removes a message listener from the forwarder list.
<T extends BusMessage> void	sendMessage(String senderAgent, Bus bus, T message) Sends a message on a bus for a given MessagingAccessLayer.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.lsst.ccs.messaging.BusMessagingLayer

getRegisteredLocalAgents, parseDestination

Field Detail

DEFAULT_UDP_PROTOCOL

public static final String DEFAULT_UDP_PROTOCOL

See Also:

Constant Field Values

Method Detail

register

public void register(String agentName,
                     Bus... buses)
              throws IOException,
                     DuplicateAgentNameException

Description copied from interface: BusMessagingLayer

Creates low level communication entry points for a subsystem. Abstract vision is that there is a different entry point for each bus/topic.

Specified by:

register in interface BusMessagingLayer

Parameters:

agentName - name of the sending/receiving point as will be known by transport null or empty string means that the local agent will receive all messages (whatever the destination of the message is : "anonymous agent") if an agent with same name is already locally registered for these buses nothing happens (the call is idempotent), but if another agent has the same name on the network a DuplicateBusNameException may be fired (this is an optional behaviour) but this exception is reported only to the corresponding BusMembershipListener

buses - list of buses we want to connect to, if empty connects to all buses

Throws:

IOException - if connection impossible,

DuplicateAgentNameException

getRegisteredLocalAgents

public Set<String> getRegisteredLocalAgents(Bus... buses)

Description copied from interface: BusMessagingLayer

Get the list of local agents currently connected to the buses.

Specified by:

getRegisteredLocalAgents in interface BusMessagingLayer

Parameters:

buses - The buses for which we are seeking the connected agents. If empty it will report agents connected to all buses.

Returns:

The List of registered buses.

closeFor

public void closeFor(String agentName,
                     Bus... buses)

Description copied from interface: BusMessagingLayer

close entry points for a bus for an agent. calls should be idempotent.

Specified by:

closeFor in interface BusMessagingLayer

Parameters:

agentName - (if empty voids the "anonymous" agent capabilities

buses - if empty all registered buses for the agent will be closed

close

public void close()
           throws IOException

Description copied from interface: BusMessagingLayer

Close the Transport Layer. Subsequent method calls will have no effect.

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Specified by:

close in interface BusMessagingLayer

Throws:

IOException

sendMessage

public <T extends BusMessage> void sendMessage(String senderAgent,
                                               Bus bus,
                                               T message)
                                        throws IOException

Description copied from interface: MessagingLayer

Sends a message on a bus for a given MessagingAccessLayer. The name of the MessagingAccessLayer determines the origin of the bus message. note : that BusMessage should have sender and destination information but it is not the role of the communication layer to parse destination information such as "subsystem1, subsystem2" or "subsystem3/module"a.

Specified by:

sendMessage in interface MessagingLayer

Type Parameters:

T - the type of message sent on the bus

Parameters:

senderAgent - provides the name as the origin of the message

bus - the bus on which to send the message

message - the message

Throws:

IOException - this could have a list of causes if some destinations fail. as much as possible implementers will ensure that all correct destinationa are adressed: if some fail it is not mandatory to report with a special subclass of IOexception that lists all destination that failed.

See Also:

org.lsst.ccs.bus.DestinationsException

addMessageListener

public void addMessageListener(String agentName,
                               BusMessageForwarder forwarder,
                               Bus... buses)

Description copied from interface: BusMessagingLayer

Sets up callback configuration for a topic and subsystem. There could be multiple Forwarder for a given bus. All callbacks are supposed to be multithreaded

Specified by:

addMessageListener in interface BusMessagingLayer

Parameters:

agentName - if empty adds a forwarder to "anonymous" agent that receives all messages

forwarder - code that handles the incoming messages

buses - if empty the forwarder listens to all buses.

removeMessageListener

public void removeMessageListener(String agentName,
                                  BusMessageForwarder forwarder,
                                  Bus... buses)

Description copied from interface: BusMessagingLayer

Removes a message listener from the forwarder list.

Specified by:

removeMessageListener in interface BusMessagingLayer

buses - if empty forwarder is removed from all buses

connect

public void connect(MessagingAccessLayer accessLayer)
             throws DuplicateAgentNameException,
                    IOException

Description copied from interface: MessagingLayer

Connects a MessagingAccessLayer object on the buses by using its name as a unique identifier. Upon creation, if needed, all needed buses are created. Depending on the underlying implementation, the MessagingLayer allows this method to be called more than once, or throws a RuntimeException. TBD : should all the buses be created or just the ones specified by the MessagingAccessLayer ?

Specified by:

connect in interface MessagingLayer

Parameters:

accessLayer - The layer to be connected on the buses

Throws:

DuplicateAgentNameException - if the name of MessagingAccessLayer is not unique on the buses

IOException

disconnect

public void disconnect(MessagingAccessLayer accessLayers)

Description copied from interface: MessagingLayer

Remove the entry point to the buses for the given MessagingAccessLayer. At this point, the CCS buses might be closed.

Specified by:

disconnect in interface MessagingLayer

Parameters:

accessLayers - The layer to be connected on the buses