org.lsst.ccs.bus.jgroups

Class JGroupsBusMessagingLayer

java.lang.Object

org.lsst.ccs.bus.jgroups.JGroupsBusMessagingLayer

All Implemented Interfaces:

Closeable, AutoCloseable, BusMessagingLayer, 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

Fields inherited from interface org.lsst.ccs.bus.BusMessagingLayer

ANONYMOUS_AGENT

Constructor Summary

Constructors

Constructor and Description
JGroupsBusMessagingLayer() Deprecated.

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.
static org.jgroups.conf.XmlConfigurator	createXmlConfiguratorForBus(String xmlConfigurationFile, Properties properties, String bus) Creates an XmlConfiguration object for a given bus.
BusMembershipListener	getBusMembershipListener(Bus bus)
List<String>	getConnectedNames(Bus bus) gets a list of agent names connected to a bus.
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 BusPayload> void	sendMessage(String senderAgent, Bus<T> bus, T message, String... destinations) sends a message on a bus: 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.
void	setMembershipListener(BusMembershipListener listener, Bus... buses) optional operation.

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_UDP_PROTOCOL

public static final String DEFAULT_UDP_PROTOCOL

See Also:

Constant Field Values

Constructor Detail

JGroupsBusMessagingLayer

@Deprecated
public JGroupsBusMessagingLayer()

Deprecated.

there should be only one instance perJVM: it's up to the calling code to check that.

Method Detail

register

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

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,

createXmlConfiguratorForBus

public static org.jgroups.conf.XmlConfigurator createXmlConfiguratorForBus(String xmlConfigurationFile,
                                                                           Properties properties,
                                                                           String bus)

Creates an XmlConfiguration object for a given bus. This object is used to initialize a JChannel. The XmlConfiguration object is created from an xml file that is loaded from the bootstrap environment. The properties object is then scanned to find relevant values to modify XmlConfiguration object. The property keys are of the form org.lsst.ccs.jgroups.[BusIdentifier].[ProtocolName].[ProtocolPropertyName]=[ProtocolPropertyValue] Where: - BusIdentifier can be either COMMAND, LOG, STATUS if the property applied to an individual bus or ALL if it applies to all the buses. - ProtocolName is a valid JGroups protocol name as specified at http://www.jgroups.org/manual/html/protlist.html - ProtocolPropertyName is a property for the given protocol - ProtocolPropertyValue is the value to be given to it If the ProtocolName does not exist in the original xml file, a new ProtocolConfiguration object will be added to the XmlConfiguration.

Parameters:

xmlConfigurationFile - The name of the xml file to be loaded

properties - The properties object to be used to overwrite the xml file

bus - The bus for which the properties are scanned

Returns:

The XmlConfiguration object to be used to create the JChannel

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 BusPayload> void sendMessage(String senderAgent,
                                               Bus<T> bus,
                                               T message,
                                               String... destinations)
                                        throws IOException

Description copied from interface: BusMessagingLayer

sends a message on a bus: 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.

The message will be sent to all destinations plus to all the "anonymous" agents

Specified by:

sendMessage in interface BusMessagingLayer

Parameters:

senderAgent - which agent is supposed to be the initiator of the message (anonymous agents are not supposed to send message: that may fire an exception)

destinations - could be empty (means broadcast) of a single "" or a single"*" (again means broadcast) or a list of destinations (DO NOT use things such as "*", "dest1", "dest2" : this will not work!)

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:

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

setMembershipListener

public void setMembershipListener(BusMembershipListener listener,
                                  Bus... buses)

Description copied from interface: ProvidesDisconnectionInformation

optional operation. registers a listener for knowing about the agents that connect/disconnect on a bus. This method is more useful if called before any agent registration (for instance duplicate agent names will be reported to these listeners)

Specified by:

setMembershipListener in interface ProvidesDisconnectionInformation

Parameters:

listener - can be null if we want to deregister a previous listener

buses - if empty register to all buses

getConnectedNames

public List<String> getConnectedNames(Bus bus)

gets a list of agent names connected to a bus. There is no distinction between agents that are passive or not.

Specified by:

getConnectedNames in interface ProvidesDisconnectionInformation

Parameters:

bus -

Returns:

a List of names (can be empty), anonymous agents are listed with a special Name

getBusMembershipListener

public BusMembershipListener getBusMembershipListener(Bus bus)

Specified by:

getBusMembershipListener in interface ProvidesDisconnectionInformation