lime
Class LimeServer

java.lang.Object
  |
  +--lime.LimeServer

All Implemented Interfaces:

java.util.EventListener, GroupChangedListener, PropertyKeys, java.lang.Runnable

public class LimeServer

extends java.lang.Object

implements java.lang.Runnable, PropertyKeys, GroupChangedListener

The runtime support needed to run Lime on a given host.

There can be multiple Lime servers running on a single host, as long as they are started on separate ports at least 3 apart. This is because (port+1) is used for loading agents, and (port+2) is used for the group manager's SinglePhaseDisseminator. Note that other (future) detectors/disseminators could use more ports.

The server must be explicitly activated by calling the boot method.

The server also provides methods that allow an agent in it to engage the corresponding host in the Lime community. Engagement takes place as a distributed transaction that reconciles the state of the system by shuffling misplaced tuples and installing weak reaction operations among the engaging host and those already in the system. Similarly, disengagement removes a host from the community.

The server can be accessed from within a program, or started from command line using the Launcher.

Version:

7/10/2003

Author:

Amy L. Murphy, Gian Pietro Picco, Christine Julien, Chien-Liang Fok, Tom Elgin

See Also:

Launcher

Field Summary

protected static java.util.Properties	defaultProperties The default server properties.
static java.util.Properties	properties The server properties.

Fields inherited from interface lime.PropertyKeys

CONNECTkey, DEBUGkey, ENGAGEkey, ENGAGEMENT_MODEkey, ERRORSkey, GM_DETECTORkey, GM_DISSEMINATORkey, GM_MAX_SPEEDkey, GM_MCASTADDRkey, GM_MCASTPORTkey, GM_NETWORK_LATENCYkey, GM_PERIODkey, GM_RANGEkey, GPS_BAUDkey, GPS_PORTkey, LOADkey, MESSAGESkey, PORTkey, QUITkey, TSFACTORYkey

Method Summary

void	boot() Activate the runtime support.
void	disengage() Start the disengagement protocol needed to allow a host to depart from a community of mobile hosts.
void	engage() Start the engagement protocol necessary to make this host part of a community of mobile hosts.
int	getLoadPort() Returns the port used to load agents onto this LimeServer.
LimeServerID	getmcastServerID() Returns the ID of the multicast server.
int	getPort() Returns the port being used by this LIMEServer.
static LimeServer	getServer() Return a handle to the Lime server.
LimeServerID	getServerID() Returns the ID of the local server.
java.lang.String	getTupleSpaceFactory() Returns the tuple space factory
void	groupChanged(GroupChangedEvent gce) The makeup of the group has changed.
boolean	isDebugOn() Returns true if debug messages should be printed.
boolean	isEngaged() Return true if the host is engaged, false otherwise
boolean	isErrorsOn() Returns true if error messages should be printed.
boolean	isMessagesOn() Returns true if messages should be printed.
boolean	isPermanentConnections() Returns true if TCP connections are maintained.
boolean	isShuttingDown() Returns whether shutdown has been called on this LimeServer.
ILimeAgent	loadAgent(java.lang.String classname, java.io.Serializable[] parameters) Load an agent into the Lime server.
void	run() Listens on the load port, when a client connects, it passes in the name of the agent that should be loaded into the LimeServer.
void	setProperty(java.lang.String key, java.lang.String value)
void	shutdown(boolean exit) Shuts down the LimeServer.

Methods inherited from class java.lang.Object

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

Field Detail

defaultProperties

protected static java.util.Properties defaultProperties

The default server properties.

properties

public static java.util.Properties properties

The server properties.

Method Detail

groupChanged

public void groupChanged(GroupChangedEvent gce)

The makeup of the group has changed. This is the required method for completely implementing the GroupChangedListener. When the Group Manager has a new set of group members, it generates an event and passes it to this registered listener. This method then takes that event and processes it, calling the engage method if the new group is larger than the previous, and disengage if the new group is smaller.

Specified by:

groupChanged in interface GroupChangedListener

Parameters:

gce - the GroupChangedEvent

setProperty

public void setProperty(java.lang.String key,
                        java.lang.String value)

getServer

public static LimeServer getServer()

Return a handle to the Lime server.

getTupleSpaceFactory

public java.lang.String getTupleSpaceFactory()

Returns the tuple space factory

getServerID

public LimeServerID getServerID()

Returns the ID of the local server.

Returns:

the ID of the local server.

getmcastServerID

public LimeServerID getmcastServerID()

Returns the ID of the multicast server.

Returns:

the ID of the multicast server.

getPort

public int getPort()

Returns the port being used by this LIMEServer.

getLoadPort

public int getLoadPort()

Returns the port used to load agents onto this LimeServer.

isPermanentConnections

public boolean isPermanentConnections()

Returns true if TCP connections are maintained.

isDebugOn

public boolean isDebugOn()

Returns true if debug messages should be printed.

isErrorsOn

public boolean isErrorsOn()

Returns true if error messages should be printed.

isMessagesOn

public boolean isMessagesOn()

Returns true if messages should be printed.

engage

public void engage()

Start the engagement protocol necessary to make this host part of a community of mobile hosts. If there are no other host to engage with, this method will block all the processing on the host until another host to engage with (a leader) is found. Host engagement is allowed only if there is at least one agent with a shared tuple space is present at that host. Engagement has no effect if the host is already engaged, i.e., no engagement protocol is run in this case.

disengage

public void disengage()

Start the disengagement protocol needed to allow a host to depart from a community of mobile hosts. If the host is already disengaged, this method has no effect, i.e., the disengagement protocol is not run.

isEngaged

public boolean isEngaged()

Return true if the host is engaged, false otherwise

loadAgent

public ILimeAgent loadAgent(java.lang.String classname,
                            java.io.Serializable[] parameters)
                     throws AgentCreationException

Load an agent into the Lime server. The agent's class is described by a fully specified class name. The bytecode (.class files) for this class and all the other classes needed by the agent must be in a directory in the same CLASSPATH available to the Lime server (and to the tuple space engine, if the latter employs user-defined classes). If the Agent subclass has a constructor with parameters, it is possible to create the agent by supplying parameters in the method call. The correct constructor is automatically retrieved by the system based on the signature.

Parameters:

classname - the fully specified name of the agent's class.

parameters - the parameters for instantiating the agent. Their type must match the type of a constructor of classname.

Returns:

a reference to the newly created ILimeAgent.

Throws:

AgentCreationException - if it is impossible to create the agent, e.g., because classname is not a subclass of ILimeAgent, or the corresponding classes cannot be found.

boot

public void boot()

Activate the runtime support.

shutdown

public void shutdown(boolean exit)

Shuts down the LimeServer.

Parameters:

exit - true if the method should system.exit

isShuttingDown

public boolean isShuttingDown()

Returns whether shutdown has been called on this LimeServer. This is used by the TransactionMgr after it has finished processing a host disengagement transaction.

run

public void run()

Listens on the load port, when a client connects, it passes in the name of the agent that should be loaded into the LimeServer. It continuously loads agents.

Specified by:

run in interface java.lang.Runnable