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org.jgroups.protocols.pbcast
Class GMS  

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

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public class GMS

extends org.jgroups.stack.Protocol

Group membership protocol. Handles joins/leaves/crashes (suspicions) and emits new views accordingly. Use VIEW_ENFORCER on top of this layer to make sure new members don't receive any messages until they are members.

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Nested Class Summary
static class	GMS.GmsHeader
static class	GMS.Request
(package private)  class	GMS.ViewHandler           Class which processes JOIN, LEAVE and MERGE requests.

 

Field Summary
(package private)  org.jgroups.util.AckCollector	ack_collector           To collect VIEW_ACKs from all members
(package private) static java.lang.String	CLIENT
(package private) static java.lang.String	COORD
private  java.lang.Object	digest_mutex
private  org.jgroups.util.Promise	digest_promise
private  long	digest_timeout
(package private)  boolean	disable_initial_coord
(package private)  boolean	handle_concurrent_startup           Setting this to false disables concurrent startups.
private  GmsImpl	impl
private  java.lang.Object	impl_mutex
private  java.util.Hashtable	impls
(package private)  long	join_retry_timeout
(package private)  long	join_timeout
private  java.util.Vector	joining           Members joined but for which no view has been received yet
(package private)  long	leave_timeout
private  java.util.Vector	leaving           Members excluded from group, but for which no view has been received yet
(package private)  org.jgroups.Address	local_addr
private  long	ltime
(package private)  org.jgroups.Membership	members
(package private)  boolean	merge_leader
(package private)  long	merge_timeout
(package private) static java.lang.String	name
protected  int	num_prev_mbrs           Max number of old members to keep in history
(package private)  int	num_views
(package private) static java.lang.String	PART
(package private)  org.jgroups.util.BoundedList	prev_members           Keeps track of old members (up to num_prev_mbrs)
(package private)  org.jgroups.util.BoundedList	prev_views           Stores the last 20 views
private  boolean	print_local_addr
private  boolean	shun
(package private)  org.jgroups.util.TimeScheduler	timer
private  org.jgroups.Membership	tmp_members
(package private)  org.jgroups.View	view
(package private)  long	view_ack_collection_timeout           Time in ms to wait for all VIEW acks (0 == wait forever)
GMS.ViewHandler	view_handler           Class to process JOIN, LEAVE and MERGE requests
(package private)  org.jgroups.ViewId	view_id

 

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

GMS()

 

Method Summary
void	becomeClient()
void	becomeCoordinator()
void	becomeParticipant()
void	castViewChange(java.util.Vector new_mbrs, java.util.Vector old_mbrs, java.util.Vector suspected_mbrs)           Compute a new view, given the current view, the new members and the suspected/left members.
void	castViewChange(org.jgroups.View new_view, Digest digest)
protected  boolean	checkSelfInclusion(java.util.Vector mbrs)           Returns true if local_addr is member of mbrs, else false
protected  org.jgroups.Address	determineCoordinator()
void	down(org.jgroups.Event evt)           An event is to be sent down the stack.
Digest	getDigest()           Sends down a GET_DIGEST event and waits for the GET_DIGEST_OK response, or timeout, whichever occurs first
GmsImpl	getImpl()
long	getJoinRetryTimeout()
long	getJoinTimeout()
java.lang.String	getLocalAddress()
(package private)  org.apache.commons.logging.Log	getLog()
java.lang.String	getMembers()
java.lang.String	getName()
org.jgroups.View	getNextView(java.util.Vector new_mbrs, java.util.Vector old_mbrs, java.util.Vector suspected_mbrs)           Computes the next view.
int	getNumberOfViews()
int	getNumMembers()
java.lang.String	getView()
(package private)  boolean	haveCoordinatorRole()
void	init()           Called after instance has been created (null constructor) and before protocol is started.
(package private)  void	initState()
void	installView(org.jgroups.View new_view)           Sets the new view and sends a VIEW_CHANGE event up and down the stack.
void	installView(org.jgroups.View new_view, Digest digest)           Sets the new view and sends a VIEW_CHANGE event up and down the stack.
boolean	isCoordinator()
boolean	isShun()
org.jgroups.View	makeView(java.util.Vector mbrs)
org.jgroups.View	makeView(java.util.Vector mbrs, org.jgroups.ViewId vid)
void	mergeDigest(Digest d)           Send down a MERGE_DIGEST event
java.lang.String	printPreviousMembers()
java.lang.String	printPreviousViews()
void	receiveUpEvent(org.jgroups.Event evt)           This method is overridden to avoid hanging on getDigest(): when a JOIN is received, the coordinator needs to retrieve the digest from the NAKACK layer.
java.util.Vector	requiredDownServices()           List of events that are required to be answered by some layer below.
void	resetStats()
void	setDigest(Digest d)           Send down a SET_DIGEST event
void	setImpl(GmsImpl new_impl)
void	setJoinRetryTimeout(long t)
void	setJoinTimeout(long t)
boolean	setProperties(java.util.Properties props)           Setup the Protocol instance according to the configuration string
void	setShun(boolean s)
void	start()           This method is called on a Channel.connect(String)>Channel.connect(String) 55 .
void	stop()           This method is called on a Channel.disconnect()>Channel.disconnect() 55 .
void	up(org.jgroups.Event evt)           An event was received from the layer below.
protected  boolean	wouldBeNewCoordinator(org.jgroups.Address potential_new_coord)           Checks whether the potential_new_coord would be the new coordinator (2nd in line)

 

Methods inherited from class org.jgroups.stack.Protocol

destroy, downThreadEnabled, dumpStats, enableStats, getDownProtocol, getDownQueue, getProperties, getUpProtocol, getUpQueue, handleSpecialDownEvent, isTrace, isWarn, passDown, passUp, printStats, providedDownServices, providedUpServices, receiveDownEvent, 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

impl

private GmsImpl impl

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local_addr

org.jgroups.Address local_addr

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members

final org.jgroups.Membership members

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tmp_members

private final org.jgroups.Membership tmp_members

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joining

private final java.util.Vector joining

Members joined but for which no view has been received yet

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leaving

private final java.util.Vector leaving

Members excluded from group, but for which no view has been received yet

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view

org.jgroups.View view

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view_id

org.jgroups.ViewId view_id

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ltime

private long ltime

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join_timeout

long join_timeout

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join_retry_timeout

long join_retry_timeout

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leave_timeout

long leave_timeout

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digest_timeout

private long digest_timeout

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merge_timeout

long merge_timeout

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impl_mutex

private final java.lang.Object impl_mutex

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digest_mutex

private final java.lang.Object digest_mutex

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digest_promise

private final org.jgroups.util.Promise digest_promise

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impls

private final java.util.Hashtable impls

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shun

private boolean shun

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merge_leader

boolean merge_leader

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print_local_addr

private boolean print_local_addr

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disable_initial_coord

boolean disable_initial_coord

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handle_concurrent_startup

boolean handle_concurrent_startup

Setting this to false disables concurrent startups. This is only used by unit testing code for testing merging. To everybody else: don't change it to false !

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CLIENT

static final java.lang.String CLIENT

See Also:

Constant Field Values

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COORD

static final java.lang.String COORD

See Also:

Constant Field Values

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PART

static final java.lang.String PART

See Also:

Constant Field Values

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timer

org.jgroups.util.TimeScheduler timer

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num_prev_mbrs

protected int num_prev_mbrs

Max number of old members to keep in history

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prev_members

org.jgroups.util.BoundedList prev_members

Keeps track of old members (up to num_prev_mbrs)

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num_views

int num_views

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prev_views

org.jgroups.util.BoundedList prev_views

Stores the last 20 views

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view_handler

public final GMS.ViewHandler view_handler

Class to process JOIN, LEAVE and MERGE requests

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ack_collector

final org.jgroups.util.AckCollector ack_collector

To collect VIEW_ACKs from all members

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view_ack_collection_timeout

long view_ack_collection_timeout

Time in ms to wait for all VIEW acks (0 == wait forever)

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name

static final java.lang.String name

See Also:

Constant Field Values

Constructor Detail

GMS

public GMS()

Method Detail

getName

public java.lang.String getName()

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getView

public java.lang.String getView()

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getNumberOfViews

public int getNumberOfViews()

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getLocalAddress

public java.lang.String getLocalAddress()

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getMembers

public java.lang.String getMembers()

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getNumMembers

public int getNumMembers()

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getJoinTimeout

public long getJoinTimeout()

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setJoinTimeout

public void setJoinTimeout(long t)

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getJoinRetryTimeout

public long getJoinRetryTimeout()

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setJoinRetryTimeout

public void setJoinRetryTimeout(long t)

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isShun

public boolean isShun()

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setShun

public void setShun(boolean s)

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printPreviousMembers

public java.lang.String printPreviousMembers()

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getLog

org.apache.commons.logging.Log getLog()

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printPreviousViews

public java.lang.String printPreviousViews()

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isCoordinator

public boolean isCoordinator()

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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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setImpl

public void setImpl(GmsImpl new_impl)

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getImpl

public GmsImpl getImpl()

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init

public void init()
          throws java.lang.Exception

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

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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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becomeCoordinator

public void becomeCoordinator()

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becomeParticipant

public void becomeParticipant()

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becomeClient

public void becomeClient()

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haveCoordinatorRole

boolean haveCoordinatorRole()

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getNextView

public org.jgroups.View getNextView(java.util.Vector new_mbrs,
                                    java.util.Vector old_mbrs,
                                    java.util.Vector suspected_mbrs)

Computes the next view. Returns a copy that has old_mbrs and suspected_mbrs removed and new_mbrs added.

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castViewChange

public void castViewChange(java.util.Vector new_mbrs,
                           java.util.Vector old_mbrs,
                           java.util.Vector suspected_mbrs)

Compute a new view, given the current view, the new members and the suspected/left members. Then simply mcast the view to all members. This is different to the VS GMS protocol, in which we run a FLUSH protocol which tries to achive consensus on the set of messages mcast in the current view before proceeding to install the next view. The members for the new view are computed as follows:

     existing          leaving        suspected          joining

     1. new_view      y                 n               n                 y
     2. tmp_view      y                 y               n                 y
     (view_dest)
     

1. The new view to be installed includes the existing members plus the joining ones and excludes the leaving and suspected members.
2. A temporary view is sent down the stack as an event. This allows the bottom layer (e.g. UDP or TCP) to determine the members to which to send a multicast message. Compared to the new view, leaving members are included since they have are waiting for a view in which they are not members any longer before they leave. So, if we did not set a temporary view, joining members would not receive the view (signalling that they have been joined successfully). The temporary view is essentially the current view plus the joining members (old members are still part of the current view).

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castViewChange

public void castViewChange(org.jgroups.View new_view,
                           Digest digest)

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installView

public void installView(org.jgroups.View new_view,
                        Digest digest)

Sets the new view and sends a VIEW_CHANGE event up and down the stack. If the view is a MergeView (subclass of View), then digest will be non-null and has to be set before installing the view.

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installView

public void installView(org.jgroups.View new_view)

Sets the new view and sends a VIEW_CHANGE event up and down the stack.

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determineCoordinator

protected org.jgroups.Address determineCoordinator()

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wouldBeNewCoordinator

protected boolean wouldBeNewCoordinator(org.jgroups.Address potential_new_coord)

Checks whether the potential_new_coord would be the new coordinator (2nd in line)

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checkSelfInclusion

protected boolean checkSelfInclusion(java.util.Vector mbrs)

Returns true if local_addr is member of mbrs, else false

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makeView

public org.jgroups.View makeView(java.util.Vector mbrs)

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makeView

public org.jgroups.View makeView(java.util.Vector mbrs,
                                 org.jgroups.ViewId vid)

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setDigest

public void setDigest(Digest d)

Send down a SET_DIGEST event

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mergeDigest

public void mergeDigest(Digest d)

Send down a MERGE_DIGEST event

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getDigest

public Digest getDigest()

Sends down a GET_DIGEST event and waits for the GET_DIGEST_OK response, or timeout, whichever occurs first

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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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receiveUpEvent

public void receiveUpEvent(org.jgroups.Event evt)

This method is overridden to avoid hanging on getDigest(): when a JOIN is received, the coordinator needs to retrieve the digest from the NAKACK layer. It therefore sends down a GET_DIGEST event, to which the NAKACK layer responds with a GET_DIGEST_OK event.

However, the GET_DIGEST_OK event will not be processed because the thread handling the JOIN request won't process the GET_DIGEST_OK event until the JOIN event returns. The receiveUpEvent() method is executed by the up-handler thread of the lower protocol and therefore can handle the event. All we do here is unblock the mutex on which JOIN is waiting, allowing JOIN to return with a valid digest. The GET_DIGEST_OK event is then discarded, because it won't be processed twice.

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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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setProperties

public boolean setProperties(java.util.Properties props)

Setup the Protocol instance according to the configuration string

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initState

void initState()

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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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