JavaGroups.JavaStack.Protocols
Class FD_RAND

java.lang.Object
  |
  +--JavaGroups.JavaStack.Protocol
        |
        +--JavaGroups.JavaStack.Protocols.FD_RAND

public class FD_RAND

extends Protocol

implements java.lang.Runnable

Failure detection based on simple heartbeat protocol. Regularly polls randomly selected members for liveness. Passes SUSPECT message up the stack when a member is not reachable. The simple algorithms works as follows: the membership is known. Each HB protocol periodically sends a 'are-you-alive' message to a randomly selected member, except itself. When a response hasn't been received for n milliseconds and m tries, the corresponding member is suspected (and eventually excluded if faulty).

FD_RAND starts when it detects (in a view change notification) that there are at least 2 members in the group. It stops running when the membership drops below 2.

Constructor Summary

FD_RAND()

Method Summary

void	Down(Event evt) An event is to be sent down the stack.
java.lang.String	GetName()
void	run() Loop while more than 1 member available.
boolean	SetProperties(java.util.Properties props) Configures the protocol initially.
void	Up(Event evt) An event was received from the layer below.

Methods inherited from class JavaGroups.JavaStack.Protocol

GetDownProtocol, GetProperties, GetUpProtocol, PassDown, PassUp, ProvidedDownServices, ProvidedUpServices, RequiredDownServices, RequiredUpServices, Reset, SetDownProtocol, SetProtocolStack, SetUpProtocol, StartDownHandler, StartUpHandler, StopInternal

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

FD_RAND

public FD_RAND()

Method Detail

GetName

public java.lang.String GetName()

Overrides:

GetName 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

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

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.

Specified by:

run in interface java.lang.Runnable