org.jgroups.protocols
Class UNICAST
java.lang.Object
org.jgroups.stack.Protocol
org.jgroups.protocols.UNICAST
- All Implemented Interfaces:
- AckSenderWindow.RetransmitCommand
public class UNICAST
- extends Protocol
- implements AckSenderWindow.RetransmitCommand
Reliable unicast layer. Uses acknowledgement scheme similar to TCP to provide lossless transmission
of unicast messages (for reliable multicast see NAKACK layer). When a message is sent to a peer for
the first time, we add the pair to the hashtable (peer address is the key). All
messages sent to that peer will be added to hashtable.peer_addr.sent_msgs. When we receive a
message from a peer for the first time, another entry will be created and added to the hashtable
(unless already existing). Msgs will then be added to hashtable.peer_addr.received_msgs. This
layer is used to reliably transmit point-to-point messages, that is, either messages sent to a
single receiver (vs. messages multicast to a group) or for example replies to a multicast message. The
sender uses an AckSenderWindow
which retransmits messages for which it hasn't received
an ACK, the receiver uses AckReceiverWindow
which keeps track of the lowest seqno
received so far, and keeps messages in order.
Messages in both AckSenderWindows and AckReceiverWindows will be removed. A message will be removed from
AckSenderWindow when an ACK has been received for it and messages will be removed from AckReceiverWindow
whenever a message is received: the new message is added and then we try to remove as many messages as
possible (until we stop at a gap, or there are no more messages).
- Author:
- Bela Ban
Fields inherited from class org.jgroups.stack.Protocol |
down_handler, down_prot, down_queue, down_thread, down_thread_prio, log, observer, props, stack, stats, up_handler, up_prot, up_queue, up_thread, up_thread_prio |
Methods inherited from class org.jgroups.stack.Protocol |
destroy, downThreadEnabled, enableStats, getDownProtocol, getDownQueue, getProperties, getUpProtocol, getUpQueue, handleSpecialDownEvent, init, passDown, passUp, printStats, providedDownServices, providedUpServices, receiveDownEvent, receiveUpEvent, requiredDownServices, requiredUpServices, setDownProtocol, setObserver, setPropertiesInternal, setProtocolStack, setUpProtocol, startDownHandler, startUpHandler, statsEnabled, stopInternal, upThreadEnabled |
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
UNICAST
public UNICAST()
getName
public java.lang.String getName()
- All protocol names have to be unique !
- Specified by:
getName
in class Protocol
getLocalAddress
public java.lang.String getLocalAddress()
getMembers
public java.lang.String getMembers()
printConnections
public java.lang.String printConnections()
getNumMessagesSent
public long getNumMessagesSent()
getNumMessagesReceived
public long getNumMessagesReceived()
getNumBytesSent
public long getNumBytesSent()
getNumBytesReceived
public long getNumBytesReceived()
getNumAcksSent
public long getNumAcksSent()
getNumAcksReceived
public long getNumAcksReceived()
getNumberOfRetransmitRequestsReceived
public long getNumberOfRetransmitRequestsReceived()
getNumberOfUnackedMessages
public int getNumberOfUnackedMessages()
- The number of messages in all Entry.sent_msgs tables (haven't received an ACK yet)
getUnackedMessages
public java.lang.String getUnackedMessages()
getNumberOfMessagesInReceiveWindows
public int getNumberOfMessagesInReceiveWindows()
resetStats
public void resetStats()
- Overrides:
resetStats
in class Protocol
dumpStats
public java.util.Map dumpStats()
- Overrides:
dumpStats
in class Protocol
setProperties
public boolean setProperties(java.util.Properties props)
- 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
start
public void start()
throws java.lang.Exception
- Description copied from class:
Protocol
- 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.
- Overrides:
start
in class Protocol
- 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()
- Description copied from class:
Protocol
- 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
- Overrides:
stop
in class Protocol
up
public void up(Event evt)
- 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 evt)
- 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
retransmit
public void retransmit(long seqno,
Message msg)
- Called by AckSenderWindow to resend messages for which no ACK has been received yet
- Specified by:
retransmit
in interface AckSenderWindow.RetransmitCommand
Copyright ? 1998-2006 Bela Ban. All Rights Reserved.