org.jgroups.protocols
Class UNICAST
- 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).
down_handler , down_prot , down_queue , down_thread , down_thread_prio , log , observer , props , stack , up_handler , up_prot , up_queue , up_thread , up_thread_prio |
destroy , down , getDownProtocol , getDownQueue , getName , getProperties , getUpProtocol , getUpQueue , handleSpecialDownEvent , init , passDown , passUp , providedDownServices , providedUpServices , receiveDownEvent , receiveUpEvent , requiredDownServices , requiredUpServices , setDownProtocol , setObserver , setProperties , setPropertiesInternal , setProtocolStack , setUpProtocol , start , startDownHandler , startUpHandler , stop , stopInternal , up |
down
public void 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 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()
.
- down in interface Protocol
getName
public String getName()
All protocol names have to be unique !
- getName in interface Protocol
setProperties
public boolean setProperties(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"
- setProperties in interface Protocol
start
public void start()
throws 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.
- start in interface Protocol
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
- stop in interface Protocol
up
public void 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 passDown()
or c) the event (or another event) is sent up
the stack using passUp()
.
- up in interface Protocol
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