org.jgroups.protocols

Class FD_SIMPLE


public class FD_SIMPLE
extends Protocol

Simple failure detection protocol. Periodically sends a are-you-alive message to a randomly chosen member (excluding itself) and waits for a response. If a response has not been received within timeout msecs, a counter associated with that member will be incremented. If the counter exceeds max_missed_hbs, that member will be suspected. When a message or a heartbeat are received, the counter is reset to 0.
Version:
$Revision: 1.9 $
Author:
Bela Ban Aug 2002

Nested Class Summary

static class
FD_SIMPLE.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, stats, trace, up_handler, up_prot, up_queue, up_thread, up_thread_prio, warn

Method Summary

void
down(Event evt)
An event is to be sent down the stack.
String
getName()
void
init()
Called after instance has been created (null constructor) and before protocol is started.
boolean
setProperties(Properties props)
Configures the protocol initially.
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, downThreadEnabled, dumpStats, enableStats, getDownProtocol, getDownQueue, getName, getProperties, getUpProtocol, getUpQueue, handleSpecialDownEvent, init, isTrace, isWarn, passDown, passUp, printStats, providedDownServices, providedUpServices, receiveDownEvent, receiveUpEvent, requiredDownServices, requiredUpServices, resetStats, setDownProtocol, setObserver, setProperties, setPropertiesInternal, setProtocolStack, setTrace, setUpProtocol, setWarn, start, startDownHandler, startUpHandler, statsEnabled, stop, stopInternal, up, upThreadEnabled

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

init

public void init()
            throws 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.
Overrides:
init 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"
 
Overrides:
setProperties 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

Copyright B) 1998-2005 Bela Ban. All Rights Reserved.