org.jgroups.protocols

Class FD_PROB

Implemented Interfaces:
Runnable

public class FD_PROB
extends Protocol
implements Runnable

Probabilistic failure detection protocol based on "A Gossip-Style Failure Detection Service" by Renesse, Minsky and Hayden.

Each member maintains a list of all other members: for each member P, 2 data are maintained, a heartbeat counter and the time of the last increment of the counter. Each member periodically sends its own heartbeat counter list to a randomly chosen member Q. Q updates its own heartbeat counter list and the associated time (if counter was incremented). Each member periodically increments its own counter. If, when sending its heartbeat counter list, a member P detects that another member Q's heartbeat counter was not incremented for timeout seconds, Q will be suspected.

This protocol can be used both with a PBCAST *and* regular stacks.

Version:
$Revision: 1.5 $

Author:
Bela Ban 1999

Nested Class Summary

static class
FD_PROB.FdHeader

Field Summary

Fields inherited from class org.jgroups.stack.Protocol

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

Method Summary

void
down(Event evt)
An event is to be sent down the stack.
String
getName()
void
run()
Loop while more than 1 member available.
boolean
setProperties(Properties props)
Configures the protocol initially.
void
start()
This method is called on a Channel.connect(String).
void
stop()
This method is called on a Channel.disconnect().
void
up(Event evt)
An event was received from the layer below.

Methods inherited from class org.jgroups.stack.Protocol

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

Method Details

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().
Overrides:
down in interface Protocol


getName

public String getName()
Overrides:
getName in interface Protocol


run

public void run()
Loop while more than 1 member available. Choose a member randomly (not myself !) and send a heartbeat. Wait for ack. If ack not received withing timeout, mcast SUSPECT message.


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"
 
Overrides:
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.
Overrides:
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
Overrides:
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().
Overrides:
up in interface Protocol


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