org.jgroups.stack
Class Protocol

java.lang.Object
  extended by org.jgroups.stack.Protocol
Direct Known Subclasses:
AUTH, AUTOCONF, BARRIER, BSH, CAUSAL, COMPRESS, DELAY, DELAY_JOIN_REQ, DISCARD, DISCARD_PAYLOAD, Discovery, DUMMY_TP, DUPL, ENCRYPT, EXAMPLE, FC, FD, FD_ALL, FD_SIMPLE, FD_SOCK, FLUSH, FRAG, FRAG2, GMS, HDRS, HTOTAL, JMS, MERGE2, MERGE3, MERGEFAST, NAKACK, PARTITION, PERF_TP, ProtocolStack, SEQUENCER, SFC, SHUFFLE, SIZE, SMACK, STABLE, STATE_TRANSFER, STATS, STREAMING_STATE_TRANSFER, TP, TP.ProtocolAdapter, TRACE, UNICAST, VERIFY_SUSPECT, VIEW_SYNC

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.

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 !

Version:
$Id: Protocol.java,v 1.54.2.1 2008/05/22 13:23:04 belaban Exp $
Author:
Bela Ban

Field Summary
protected  Protocol down_prot
           
protected  org.apache.commons.logging.Log log
           
protected  java.util.Properties props
           
protected  ProtocolStack stack
           
protected  boolean stats
           
protected  Protocol up_prot
           
 
Constructor Summary
Protocol()
           
 
Method Summary
 void destroy()
          This method is called on a Channel.close().
 java.lang.Object down(Event evt)
          An event is to be sent down the stack.
 boolean downThreadEnabled()
          Deprecated. down thread was removed
 java.util.Map<java.lang.String,java.lang.Object> dumpStats()
           
 void enableStats(boolean flag)
           
 Protocol getDownProtocol()
           
abstract  java.lang.String getName()
           
 java.util.Properties getProperties()
           
 ProtocolStack getProtocolStack()
           
 ThreadFactory getThreadFactory()
          Supposed to be overwritten by subclasses.
protected  TP getTransport()
           
 Protocol getUpProtocol()
           
 void init()
          Called after instance has been created (null constructor) and before protocol is started.
 java.lang.String printStats()
           
 java.util.Vector<java.lang.Integer> providedDownServices()
          List of events that are provided to layers below (they will be handled when sent down from below).
 java.util.Vector<java.lang.Integer> providedUpServices()
          List of events that are provided to layers above (they will be handled when sent down from above).
 java.util.Vector<java.lang.Integer> requiredDownServices()
          List of events that are required to be answered by some layer below.
 java.util.Vector<java.lang.Integer> requiredUpServices()
          List of events that are required to be answered by some layer above.
 void resetStats()
           
 void setDownProtocol(Protocol down_prot)
           
 boolean setProperties(java.util.Properties props)
          Configures the protocol initially.
 boolean setPropertiesInternal(java.util.Properties props)
          Called by Configurator.
 void setProtocolStack(ProtocolStack stack)
           
 void setUpProtocol(Protocol up_prot)
           
 void start()
          This method is called on a Channel.connect(String).
 boolean statsEnabled()
           
 void stop()
          This method is called on a Channel.disconnect().
 java.lang.Object up(Event evt)
          An event was received from the layer below.
 boolean upThreadEnabled()
          Deprecated. up_thread was removed
 
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

stats

protected boolean stats

log

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

getProtocolStack

public ProtocolStack getProtocolStack()

getTransport

protected TP getTransport()

getThreadFactory

public ThreadFactory getThreadFactory()
Supposed to be overwritten by subclasses. Usually the transport returns a valid non-null thread factory, but thread factories can also be created by individual protocols

Returns:

upThreadEnabled

public boolean upThreadEnabled()
Deprecated. up_thread was removed

Returns:
false by default

downThreadEnabled

public boolean downThreadEnabled()
Deprecated. down thread was removed

Returns:
boolean False by default

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<java.lang.String,java.lang.Object> dumpStats()

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.

Throws:
java.lang.Exception - Thrown if protocol cannot be initialized successfully. This will cause the ProtocolStack to fail, so the channel constructor will throw an exception

start

public void start()
           throws java.lang.Exception
This method is called on a Channel.connect(String). 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.

Throws:
java.lang.Exception - Thrown if protocol cannot be started successfully. This will cause the ProtocolStack to fail, so Channel.connect(String) will throw an exception

stop

public void stop()
This method is called on a Channel.disconnect(). 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(). Does some cleanup; after the call the VM will terminate


requiredUpServices

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

Returns:
Vector (of Integers)

requiredDownServices

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

Returns:
Vector (of Integers)

providedUpServices

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

Returns:
Vector (of Integers)

providedDownServices

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

Returns:
Vector

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)

up

public java.lang.Object up(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 down_prot.down() or c) the event (or another event) is sent up the stack using up_prot.up().


down

public java.lang.Object down(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 down_prot.down(). 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 up_prot.up().



Copyright © 1998-2008 Bela Ban. All Rights Reserved.