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org.jgroups.protocols.pbcast
Class STABLE  

java.lang.Object
  org.jgroups.stack.Protocol
      org.jgroups.protocols.pbcast.STABLE

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public class STABLE

extends org.jgroups.stack.Protocol

Computes the broadcast messages that are stable; i.e., have been received by all members. Sends STABLE events up the stack when this is the case. This allows NAKACK to garbage collect messages that have been seen by all members.

Works as follows: periodically we mcast our highest seqnos (seen for each member) to the group. A stability vector, which maintains the highest seqno for each member and initially contains no data, is updated when such a message is received. The entry for a member P is computed set to min(entry[P], digest[P]). When messages from all members have been received, a stability message is mcast, which causes all members to send a STABLE event up the stack (triggering garbage collection in the NAKACK layer).

The stable task now terminates after max_num_gossips if no messages or view changes have been sent or received in the meantime. It will resume when messages are received. This effectively suspends sending superfluous STABLE messages in the face of no activity.
New: when max_bytes is exceeded (unless disabled by setting it to 0), a STABLE task will be started (unless it is already running).

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Nested Class Summary
private  class	STABLE.ResumeTask
private  class	STABLE.StabilitySendTask           Multicasts a STABILITY message.
static class	STABLE.StableHeader
private  class	STABLE.StableTask           Mcast periodic STABLE message.

 

Field Summary
(package private)  long	desired_avg_gossip           Sends a STABLE gossip every 20 seconds on average.
(package private)  Digest	digest
(package private)  java.util.Vector	heard_from
(package private)  boolean	initialized
(package private)  Digest	latest_local_digest
(package private)  org.jgroups.Address	local_addr
(package private)  long	max_bytes           Total amount of bytes from incoming messages (default = 0 = disabled).
(package private)  java.util.Vector	mbrs
(package private) static java.lang.String	name
(package private)  long	num_bytes_received           The total number of bytes received from unicast and multicast messages
(package private)  int	num_gossips           Number of gossip messages
(package private)  STABLE.ResumeTask	resume_task
(package private)  java.lang.Object	resume_task_mutex
(package private)  long	stability_delay           delay before we send STABILITY msg (give others a change to send first).
(package private)  java.lang.Object	stability_mutex
(package private)  STABLE.StabilitySendTask	stability_task
(package private)  STABLE.StableTask	stable_task
(package private)  java.lang.Object	stable_task_mutex
(package private)  boolean	suspended           When true, don't take part in garbage collection protocol: neither send STABLE messages nor handle STABILITY messages
(package private)  org.jgroups.util.TimeScheduler	timer

 

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

 

Constructor Summary

STABLE()

 

Method Summary
private  void	adjustSenders(Digest d, java.util.Vector members)           Digest and members are guaranteed to be non-null
private  void	clearDigest()
void	down(org.jgroups.Event evt)           An event is to be sent down the stack.
long	getDesiredAverageGossip()
long	getMaxBytes()
java.lang.String	getName()
int	getNumberOfGossipMessages()
(package private)  void	handleStabilityMessage(Digest d, org.jgroups.Address sender)
private  void	handleStableMessage(org.jgroups.Address sender, Digest d)           Digest d contains (a) the highest seqnos deliverable for each sender and (b) the highest seqnos seen for each member.
private  void	handleViewChange(org.jgroups.View v)
private  boolean	removeFromHeardFromList(org.jgroups.Address mbr)           Removes mbr from heard_from and returns true if this was the last member, otherwise false.
java.util.Vector	requiredDownServices()           List of events that are required to be answered by some layer below.
private  void	resetDigest(java.util.Vector new_members)
void	resetStats()
private  void	resume()
void	runMessageGarbageCollection()
(package private)  void	sendStabilityMessage(Digest tmp)           Schedules a stability message to be mcast after a random number of milliseconds (range 1-5 secs).
private  void	sendStableMessage(Digest d)           Bcasts a STABLE message of the current digest to all members.
void	setDesiredAverageGossip(long gossip_interval)
void	setMaxBytes(long max_bytes)
boolean	setProperties(java.util.Properties props)           Configures the protocol initially.
void	start()           This method is called on a Channel.connect(String)>Channel.connect(String) 55 .
(package private)  void	startResumeTask(long max_suspend_time)
(package private)  void	startStabilityTask(Digest d, long delay)
(package private)  void	startStableTask()
void	stop()           This method is called on a Channel.disconnect()>Channel.disconnect() 55 .
(package private)  void	stopResumeTask()
(package private)  void	stopStabilityTask()
(package private)  void	stopStableTask()
private  void	suspend(long timeout)
void	up(org.jgroups.Event evt)           An event was received from the layer below.
private  boolean	updateLocalDigest(Digest d, org.jgroups.Address sender)           Update my own digest from a digest received by somebody else.

 

Methods inherited from class org.jgroups.stack.Protocol

destroy, downThreadEnabled, dumpStats, enableStats, getDownProtocol, getDownQueue, getProperties, getUpProtocol, getUpQueue, handleSpecialDownEvent, init, isTrace, isWarn, passDown, passUp, printStats, providedDownServices, providedUpServices, receiveDownEvent, receiveUpEvent, requiredUpServices, setDownProtocol, setObserver, setPropertiesInternal, setProtocolStack, setTrace, setUpProtocol, setWarn, startDownHandler, startUpHandler, statsEnabled, stopInternal, upThreadEnabled

 

Methods inherited from class java.lang.Object

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

 

Field Detail

local_addr

org.jgroups.Address local_addr

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mbrs

final java.util.Vector mbrs

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digest

final Digest digest

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latest_local_digest

final Digest latest_local_digest

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heard_from

final java.util.Vector heard_from

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desired_avg_gossip

long desired_avg_gossip

Sends a STABLE gossip every 20 seconds on average. 0 disables gossipping of STABLE messages

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stability_delay

long stability_delay

delay before we send STABILITY msg (give others a change to send first). This should be set to a very small number (> 0 !) if max_bytes is used

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stability_task

STABLE.StabilitySendTask stability_task

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stability_mutex

final java.lang.Object stability_mutex

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stable_task

STABLE.StableTask stable_task

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stable_task_mutex

final java.lang.Object stable_task_mutex

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timer

org.jgroups.util.TimeScheduler timer

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name

static final java.lang.String name

See Also:

Constant Field Values

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max_bytes

long max_bytes

Total amount of bytes from incoming messages (default = 0 = disabled). When exceeded, a STABLE message will be broadcast and num_bytes_received reset to 0 . If this is > 0, then ideally stability_delay should be set to a low number as well

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num_bytes_received

long num_bytes_received

The total number of bytes received from unicast and multicast messages

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suspended

boolean suspended

When true, don't take part in garbage collection protocol: neither send STABLE messages nor handle STABILITY messages

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initialized

boolean initialized

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resume_task

STABLE.ResumeTask resume_task

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resume_task_mutex

final java.lang.Object resume_task_mutex

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num_gossips

int num_gossips

Number of gossip messages

Constructor Detail

STABLE

public STABLE()

Method Detail

getName

public java.lang.String getName()

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getDesiredAverageGossip

public long getDesiredAverageGossip()

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setDesiredAverageGossip

public void setDesiredAverageGossip(long gossip_interval)

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getMaxBytes

public long getMaxBytes()

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setMaxBytes

public void setMaxBytes(long max_bytes)

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getNumberOfGossipMessages

public int getNumberOfGossipMessages()

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resetStats

public void resetStats()

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requiredDownServices

public java.util.Vector requiredDownServices()

Description copied from class: org.jgroups.stack.Protocol

List of events that are required to be answered by some layer below.

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setProperties

public boolean setProperties(java.util.Properties props)

Description copied from class: org.jgroups.stack.Protocol

Configures the protocol initially. A configuration string consists of name=value items, separated by a ';' (semicolon), e.g.:

 "loopback=false;unicast_inport=4444"
 

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suspend

private void suspend(long timeout)

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resume

private void resume()

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start

public void start()
           throws java.lang.Exception

Description copied from class: org.jgroups.stack.Protocol

This method is called on a Channel.connect(String)>Channel.connect(String) 55 . 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.

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stop

public void stop()

Description copied from class: org.jgroups.stack.Protocol

This method is called on a Channel.disconnect()>Channel.disconnect() 55 . 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

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up

public void up(org.jgroups.Event evt)

Description copied from class: org.jgroups.stack.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().

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down

public void down(org.jgroups.Event evt)

Description copied from class: org.jgroups.stack.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().

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runMessageGarbageCollection

public void runMessageGarbageCollection()

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handleViewChange

private void handleViewChange(org.jgroups.View v)

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adjustSenders

private void adjustSenders(Digest d,
                           java.util.Vector members)

Digest and members are guaranteed to be non-null

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clearDigest

private void clearDigest()

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updateLocalDigest

private boolean updateLocalDigest(Digest d,
                                  org.jgroups.Address sender)

Update my own digest from a digest received by somebody else. Returns whether the update was successful. Needs to be called with a lock on digest

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resetDigest

private void resetDigest(java.util.Vector new_members)

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removeFromHeardFromList

private boolean removeFromHeardFromList(org.jgroups.Address mbr)

Removes mbr from heard_from and returns true if this was the last member, otherwise false. Resets the heard_from list (populates with membership)

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startStableTask

void startStableTask()

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stopStableTask

void stopStableTask()

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startResumeTask

void startResumeTask(long max_suspend_time)

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stopResumeTask

void stopResumeTask()

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startStabilityTask

void startStabilityTask(Digest d,
                        long delay)

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stopStabilityTask

void stopStabilityTask()

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handleStableMessage

private void handleStableMessage(org.jgroups.Address sender,
                                 Digest d)

Digest d contains (a) the highest seqnos deliverable for each sender and (b) the highest seqnos seen for each member. (Difference: with 1,2,4,5, the highest seqno seen is 5, whereas the highest seqno deliverable is 2). The minimum of all highest seqnos deliverable will be taken to send a stability message, which results in garbage collection of messages lower than the ones in the stability vector. The maximum of all seqnos will be taken to trigger possible retransmission of last missing seqno (see DESIGN for details).

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sendStableMessage

private void sendStableMessage(Digest d)

Bcasts a STABLE message of the current digest to all members. Message contains highest seqnos of all members seen by this member. Highest seqnos are retrieved from the NAKACK layer below.

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sendStabilityMessage

void sendStabilityMessage(Digest tmp)

Schedules a stability message to be mcast after a random number of milliseconds (range 1-5 secs). The reason for waiting a random amount of time is that, in the worst case, all members receive a STABLE_GOSSIP message from the last outstanding member at the same time and would therefore mcast the STABILITY message at the same time too. To avoid this, each member waits random N msecs. If, before N elapses, some other member sent the STABILITY message, we just cancel our own message. If, during waiting for N msecs to send STABILITY message S1, another STABILITY message S2 is to be sent, we just discard S2.

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handleStabilityMessage

void handleStabilityMessage(Digest d,
                            org.jgroups.Address sender)

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Overview  Package   Class  Use  Deprecated  Index
Home >> All >> org >> jgroups >> protocols >> [ pbcast overview ]	PREV CLASS  NEXT CLASS
SUMMARY:  JAVADOC |  SOURCE |  DOWNLOAD | NESTED | FIELD | CONSTR | METHOD	DETAIL: FIELD | CONSTR | METHOD

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