org.jgroups.protocols
Class FD

java.lang.Object
  extended by org.jgroups.stack.Protocol
      extended by org.jgroups.protocols.FD
Direct Known Subclasses:
FD_ICMP, FD_PING

public class FD
extends Protocol

Failure detection based on simple heartbeat protocol. Regularly polls members for liveness. Multicasts SUSPECT messages when a member is not reachable. The simple algorithms works as follows: the membership is known and ordered. Each HB protocol periodically sends an 'are-you-alive' message to its *neighbor*. A neighbor is the next in rank in the membership list, which is recomputed upon a view change. When a response hasn't been received for n milliseconds and m tries, the corresponding member is suspected (and eventually excluded if faulty).

FD 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.

When a message is received from the monitored neighbor member, it causes the pinger thread to 'skip' sending the next are-you-alive message. Thus, traffic is reduced.

When we receive a ping from a member that's not in the membership list, we shun it by sending it a NOT_MEMBER message. That member will then leave the group (and possibly rejoin). This is only done if shun is true.

Version:
$Id: FD.java,v 1.58.2.3 2008/05/22 13:23:06 belaban Exp $
Author:
Bela Ban

Nested Class Summary
protected  class FD.Broadcaster
          Task that periodically broadcasts a list of suspected members to the group.
protected  class FD.BroadcastTask
           
static class FD.FdHeader
           
protected  class FD.Monitor
           
 
Field Summary
protected  FD.Broadcaster bcast_task
          Transmits SUSPECT message until view change or UNSUSPECT is received
protected  java.util.concurrent.locks.Lock lock
           
protected  int num_heartbeats
           
protected  int num_suspect_events
           
 
Fields inherited from class org.jgroups.stack.Protocol
down_prot, log, props, stack, stats, up_prot
 
Constructor Summary
FD()
           
 
Method Summary
 java.lang.Object down(Event evt)
          An event is to be sent down the stack.
 int getCurrentNumTries()
           
 java.lang.String getLocalAddress()
           
 int getMaxTries()
           
 java.lang.String getMembers()
           
 java.lang.String getName()
           
 int getNumberOfHeartbeatsSent()
           
 int getNumSuspectEventsGenerated()
           
 java.lang.String getPingableMembers()
           
 java.lang.String getPingDest()
           
 long getTimeout()
           
 void init()
          Called after instance has been created (null constructor) and before protocol is started.
 boolean isShun()
           
 java.lang.String printSuspectHistory()
           
 void resetStats()
           
 void setMaxTries(int max_tries)
           
 boolean setProperties(java.util.Properties props)
          Configures the protocol initially.
 void setShun(boolean flag)
           
 void setTimeout(long timeout)
           
 void stop()
          This method is called on a Channel.disconnect().
 java.lang.Object up(Event evt)
          An event was received from the layer below.
 
Methods inherited from class org.jgroups.stack.Protocol
destroy, downThreadEnabled, dumpStats, enableStats, getDownProtocol, getProperties, getProtocolStack, getThreadFactory, getTransport, getUpProtocol, printStats, providedDownServices, providedUpServices, requiredDownServices, requiredUpServices, setDownProtocol, setPropertiesInternal, setProtocolStack, setUpProtocol, start, statsEnabled, upThreadEnabled
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

lock

protected final java.util.concurrent.locks.Lock lock

num_heartbeats

protected int num_heartbeats

num_suspect_events

protected int num_suspect_events

bcast_task

protected final FD.Broadcaster bcast_task
Transmits SUSPECT message until view change or UNSUSPECT is received

Constructor Detail

FD

public FD()
Method Detail

getName

public java.lang.String getName()
Specified by:
getName in class Protocol

getLocalAddress

public java.lang.String getLocalAddress()

getMembers

public java.lang.String getMembers()

getPingableMembers

public java.lang.String getPingableMembers()

getPingDest

public java.lang.String getPingDest()

getNumberOfHeartbeatsSent

public int getNumberOfHeartbeatsSent()

getNumSuspectEventsGenerated

public int getNumSuspectEventsGenerated()

getTimeout

public long getTimeout()

setTimeout

public void setTimeout(long timeout)

getMaxTries

public int getMaxTries()

setMaxTries

public void setMaxTries(int max_tries)

getCurrentNumTries

public int getCurrentNumTries()

isShun

public boolean isShun()

setShun

public void setShun(boolean flag)

printSuspectHistory

public java.lang.String printSuspectHistory()

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

resetStats

public void resetStats()
Overrides:
resetStats in class Protocol

init

public void init()
          throws java.lang.Exception
Description copied from class: Protocol
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 class Protocol
Throws:
java.lang.Exception - Thrown if protocol cannot be initialized successfully. This will cause the ProtocolStack to fail, so the channel constructor 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 java.lang.Object 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 down_prot.down() or c) the event (or another event) is sent up the stack using up_prot.up().

Overrides:
up in class Protocol

down

public java.lang.Object 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 down_prot.down(). 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 up_prot.up().

Overrides:
down in class Protocol


Copyright ? 1998-2008 Bela Ban. All Rights Reserved.