org.javagroups.protocols
Class TOTAL

java.lang.Object
  extended byorg.javagroups.stack.Protocol
      extended byorg.javagroups.protocols.TOTAL

public class TOTAL
extends Protocol

Implements the total ordering layer using a message sequencer

The protocol guarantees that all bcast sent messages will be delivered in the same order to all members. For that it uses a sequencer which assignes monotonically increasing sequence ID to broadcasts. Then all group members deliver the bcasts in ascending sequence ID order.

Please note that once a BLOCK_OK is acknowledged messages coming from above are discarded! Either the application must stop sending messages when a BLOCK event is received from the channel or a QUEUE layer should be placed above this one. Received messages are still delivered above though.

bcast requests are retransmitted periodically until a bcast reply is received. In case a BCAST_REP is on its way during a BCAST_REQ retransmission, then the next BCAST_REP will be to a non-existing BCAST_REQ. So, a nulll BCAST message is sent to fill the created gap in the seqID of all members.

Author:
i.georgiadis@doc.ic.ac.uk

Nested Class Summary
static class TOTAL.Header
          The header processed by the TOTAL layer and intended for TOTAL inter-stack communication
 
Field Summary
 
Fields inherited from class org.javagroups.stack.Protocol
down_handler, down_prot, down_queue, down_thread, observer, props, stack, up_handler, up_prot, up_queue, up_thread
 
Constructor Summary
TOTAL()
          Create the TOTAL layer
 
Method Summary
 void down(Event event)
          An event is to be sent down the stack.
 java.lang.String getName()
           
 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.
 boolean setProperties(java.util.Properties properties)
          Configures the protocol initially.
 void start()
          Prepare this layer to receive messages from above
 void stop()
          Handle the stop() method travelling down the stack.
 void up(Event event)
          An event was received from the layer below.
 
Methods inherited from class org.javagroups.stack.Protocol
destroy, getDownProtocol, getDownQueue, getProperties, getUpProtocol, getUpQueue, init, passDown, passUp, providedDownServices, providedUpServices, receiveDownEvent, receiveUpEvent, setDownProtocol, setObserver, setPropertiesInternal, setProtocolStack, setUpProtocol, startDownHandler, startUpHandler, stopInternal
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

TOTAL

public TOTAL()
Create the TOTAL layer

Method Detail

start

public void start()
           throws java.lang.Exception
Prepare this layer to receive messages from above

Overrides:
start in class Protocol
Returns:
true if event should be forwarded further up
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()
Handle the stop() method travelling down the stack.

The local addr is set to null, since after a Start->Stop->Start sequence this member's addr is not guaranteed to be the same

Overrides:
stop in class Protocol

getName

public java.lang.String getName()
Specified by:
getName in class Protocol

setProperties

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

Overrides:
setProperties in class Protocol

requiredDownServices

public java.util.Vector requiredDownServices()
Description copied from class: Protocol
List of events that are required to be answered by some layer below.

Overrides:
requiredDownServices in class Protocol
Returns:
Vector (of Integers)

requiredUpServices

public java.util.Vector requiredUpServices()
Description copied from class: Protocol
List of events that are required to be answered by some layer above.

Overrides:
requiredUpServices in class Protocol
Returns:
Vector (of Integers)

up

public void up(Event event)
Description copied from class: Protocol
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().

Overrides:
up in class Protocol

down

public void down(Event event)
Description copied from class: Protocol
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().

Overrides:
down in class Protocol


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