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SUMMARY: JavaDoc of org.jgroups.stack.Protocol JAVADOC | Sourc code of org.jgroups.stack.Protocol SOURCE | Download org.jgroups.stack.Protocol DOWNLOAD | NESTED | FIELD | CONSTR | METHOD DETAIL: FIELD | CONSTR | METHOD

org.jgroups.stack
Class Protocol  view Protocol download Protocol.java

java.lang.Object
  extended byorg.jgroups.stack.Protocol
Direct Known Subclasses:
MessageProtocol, ProtocolStack
public abstract class Protocol
extends java.lang.Object

The Protocol class provides a set of common services for protocol layers. Each layer has to be a subclass of Protocol and override a number of methods (typically just up(), Down and getName. Layers are stacked in a certain order to form a protocol stack. Events are passed from lower layers to upper ones and vice versa. E.g. a Message received by the UDP layer at the bottom will be passed to its higher layer as an Event. That layer will in turn pass the Event to its layer and so on, until a layer handles the Message and sends a response or discards it, the former resulting in another Event being passed down the stack.

Each layer has 2 FIFO queues, one for up Events and one for down Events. When an Event is received by a layer (calling the internal upcall ReceiveUpEvent), it is placed in the up-queue where it will be retrieved by the up-handler thread which will invoke method Up of the layer. The same applies for Events traveling down the stack. Handling of the up-handler and down-handler threads and the 2 FIFO queues is donw by the Protocol class, subclasses will almost never have to override this behavior.

The important thing to bear in mind is that Events have to passed on between layers in FIFO order which is guaranteed by the Protocol implementation and must be guranteed by subclasses implementing their on Event queuing.

Note that each class implementing interface Protocol MUST provide an empty, public constructor !

Field Summary
protected  DownHandler down_handler
           
protected  Protocol down_prot
           
protected  org.jgroups.util.Queue down_queue
           
protected  boolean down_thread
           
protected  int down_thread_prio
           
protected  org.apache.commons.logging.Log log
           
protected  ProtocolObserver observer
           
protected  java.util.Properties props
           
protected  ProtocolStack stack
           
protected  boolean stats
           
private static long THREAD_JOIN_TIMEOUT
           
protected  boolean trace
           
protected  UpHandler up_handler
           
protected  Protocol up_prot
           
protected  org.jgroups.util.Queue up_queue
           
protected  boolean up_thread
           
protected  int up_thread_prio
           
protected  boolean warn
           
 
Constructor Summary
Protocol()
           
 
Method Summary
 void destroy()
          This method is called on a Channel.close()>Channel.close() 55 .
 void down(org.jgroups.Event evt)
          An event is to be sent down the stack.
 boolean downThreadEnabled()
           
 java.util.Map dumpStats()
           
 void enableStats(boolean flag)
           
 Protocol getDownProtocol()
           
 org.jgroups.util.Queue getDownQueue()
           
abstract  java.lang.String getName()
           
 java.util.Properties getProperties()
           
 Protocol getUpProtocol()
           
 org.jgroups.util.Queue getUpQueue()
           
protected  boolean handleSpecialDownEvent(org.jgroups.Event evt)
          These are special internal events that should not be handled by protocols
 void init()
          Called after instance has been created (null constructor) and before protocol is started.
 boolean isTrace()
           
 boolean isWarn()
           
 void passDown(org.jgroups.Event evt)
          Causes the event to be forwarded to the next layer down in the hierarchy.Typically called by the implementation of Down (when done).
 void passUp(org.jgroups.Event evt)
          Causes the event to be forwarded to the next layer up in the hierarchy.
 java.lang.String printStats()
           
 java.util.Vector providedDownServices()
          List of events that are provided to layers below (they will be handled when sent down from below).
 java.util.Vector providedUpServices()
          List of events that are provided to layers above (they will be handled when sent down from above).
protected  void receiveDownEvent(org.jgroups.Event evt)
          Internal method, should not be called by clients.
protected  void receiveUpEvent(org.jgroups.Event evt)
          Internal method, should not be called by clients.
 java.util.Vector requiredDownServices()
          List of events that are required to be answered by some layer below.
 java.util.Vector requiredUpServices()
          List of events that are required to be answered by some layer above.
 void resetStats()
           
 void setDownProtocol(Protocol down_prot)
           
 void setObserver(ProtocolObserver observer)
           
 boolean setProperties(java.util.Properties props)
          Configures the protocol initially.
 boolean setPropertiesInternal(java.util.Properties props)
          Called by Configurator.
 void setProtocolStack(ProtocolStack stack)
           
 void setTrace(boolean trace)
           
 void setUpProtocol(Protocol up_prot)
           
 void setWarn(boolean warn)
           
 void start()
          This method is called on a Channel.connect(String)>Channel.connect(String) 55 .
 void startDownHandler()
          Used internally.
 void startUpHandler()
          Used internally.
 boolean statsEnabled()
           
 void stop()
          This method is called on a Channel.disconnect()>Channel.disconnect() 55 .
 void stopInternal()
          Used internally.
 void up(org.jgroups.Event evt)
          An event was received from the layer below.
 boolean upThreadEnabled()
           
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

props

protected final java.util.Properties props

up_prot

protected Protocol up_prot

down_prot

protected Protocol down_prot

stack

protected ProtocolStack stack

up_queue

protected final org.jgroups.util.Queue up_queue

down_queue

protected final org.jgroups.util.Queue down_queue

up_handler

protected UpHandler up_handler

up_thread_prio

protected int up_thread_prio

down_handler

protected DownHandler down_handler

down_thread_prio

protected int down_thread_prio

observer

protected ProtocolObserver observer

THREAD_JOIN_TIMEOUT

private static final long THREAD_JOIN_TIMEOUT
See Also:
Constant Field Values

down_thread

protected boolean down_thread

up_thread

protected boolean up_thread

stats

protected boolean stats

log

protected final org.apache.commons.logging.Log log

trace

protected boolean trace

warn

protected boolean warn
Constructor Detail

Protocol

public Protocol()
Method Detail

setProperties

public boolean setProperties(java.util.Properties props)
Configures the protocol initially. A configuration string consists of name=value items, separated by a ';' (semicolon), e.g.:
 "loopback=false;unicast_inport=4444"

setPropertiesInternal

public boolean setPropertiesInternal(java.util.Properties props)
Called by Configurator. Removes 2 properties which are used by the Protocol directly and then calls setProperties(), which might invoke the setProperties() method of the actual protocol instance.

getProperties

public java.util.Properties getProperties()

isTrace

public boolean isTrace()

setTrace

public void setTrace(boolean trace)

isWarn

public boolean isWarn()

setWarn

public void setWarn(boolean warn)

upThreadEnabled

public boolean upThreadEnabled()

downThreadEnabled

public boolean downThreadEnabled()

statsEnabled

public boolean statsEnabled()

enableStats

public void enableStats(boolean flag)

resetStats

public void resetStats()

printStats

public java.lang.String printStats()

dumpStats

public java.util.Map dumpStats()

setObserver

public void setObserver(ProtocolObserver observer)

init

public void init()
          throws java.lang.Exception
Called after instance has been created (null constructor) and before protocol is started. Properties are already set. Other protocols are not yet connected and events cannot yet be sent.

start

public void start()
           throws java.lang.Exception
This method is called on a Channel.connect(String)>Channel.connect(String) 55 . Starts work. Protocols are connected and queues are ready to receive events. Will be called from bottom to top. This call will replace the START and START_OK events.

stop

public void stop()
This method is called on a Channel.disconnect()>Channel.disconnect() 55 . Stops work (e.g. by closing multicast socket). Will be called from top to bottom. This means that at the time of the method invocation the neighbor protocol below is still working. This method will replace the STOP, STOP_OK, CLEANUP and CLEANUP_OK events. The ProtocolStack guarantees that when this method is called all messages in the down queue will have been flushed

destroy

public void destroy()
This method is called on a Channel.close()>Channel.close() 55 . Does some cleanup; after the call the VM will terminate

getUpQueue

public org.jgroups.util.Queue getUpQueue()

getDownQueue

public org.jgroups.util.Queue getDownQueue()

requiredUpServices

public java.util.Vector requiredUpServices()
List of events that are required to be answered by some layer above.

requiredDownServices

public java.util.Vector requiredDownServices()
List of events that are required to be answered by some layer below.

providedUpServices

public java.util.Vector providedUpServices()
List of events that are provided to layers above (they will be handled when sent down from above).

providedDownServices

public java.util.Vector providedDownServices()
List of events that are provided to layers below (they will be handled when sent down from below).

getName

public abstract java.lang.String getName()

getUpProtocol

public Protocol getUpProtocol()

getDownProtocol

public Protocol getDownProtocol()

setUpProtocol

public void setUpProtocol(Protocol up_prot)

setDownProtocol

public void setDownProtocol(Protocol down_prot)

setProtocolStack

public void setProtocolStack(ProtocolStack stack)

startUpHandler

public void startUpHandler()
Used internally. If overridden, call this method first. Only creates the up_handler thread if down_thread is true

startDownHandler

public void startDownHandler()
Used internally. If overridden, call this method first. Only creates the down_handler thread if down_thread is true

stopInternal

public void stopInternal()
Used internally. If overridden, call parent's method first

receiveUpEvent

protected void receiveUpEvent(org.jgroups.Event evt)
Internal method, should not be called by clients. Used by ProtocolStack. I would have used the 'friends' modifier, but this is available only in C++ ... If the up_handler thread is not available (down_thread == false), then directly call the up() method: we will run on the caller's thread (e.g. the protocol layer below us).

receiveDownEvent

protected void receiveDownEvent(org.jgroups.Event evt)
Internal method, should not be called by clients. Used by ProtocolStack. I would have used the 'friends' modifier, but this is available only in C++ ... If the down_handler thread is not available (down_thread == false), then directly call the down() method: we will run on the caller's thread (e.g. the protocol layer above us).

passUp

public void passUp(org.jgroups.Event evt)
Causes the event to be forwarded to the next layer up in the hierarchy. Typically called by the implementation of Up (when done).

passDown

public void passDown(org.jgroups.Event evt)
Causes the event to be forwarded to the next layer down in the hierarchy.Typically called by the implementation of Down (when done).

up

public void up(org.jgroups.Event evt)
An event was received from the layer below. Usually the current layer will want to examine the event type and - depending on its type - perform some computation (e.g. removing headers from a MSG event type, or updating the internal membership list when receiving a VIEW_CHANGE event). Finally the event is either a) discarded, or b) an event is sent down the stack using passDown() or c) the event (or another event) is sent up the stack using passUp().

down

public void down(org.jgroups.Event evt)
An event is to be sent down the stack. The layer may want to examine its type and perform some action on it, depending on the event's type. If the event is a message MSG, then the layer may need to add a header to it (or do nothing at all) before sending it down the stack using passDown(). In case of a GET_ADDRESS event (which tries to retrieve the stack's address from one of the bottom layers), the layer may need to send a new response event back up the stack using passUp().

handleSpecialDownEvent

protected boolean handleSpecialDownEvent(org.jgroups.Event evt)
These are special internal events that should not be handled by protocols

Overview  Package   Class  Use  Deprecated  Index 
Home >> All >> org >> jgroups >> [ stack overview ]  PREV CLASS  NEXT CLASS
SUMMARY: JavaDoc of org.jgroups.stack.Protocol JAVADOC | Sourc code of org.jgroups.stack.Protocol SOURCE | Download org.jgroups.stack.Protocol DOWNLOAD | NESTED | FIELD | CONSTR | METHOD DETAIL: FIELD | CONSTR | METHOD