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java.lang.Objectorg.jgroups.stack.Protocol
org.jgroups.protocols.pbcast.FLUSH
public class FLUSH
Flush, as it name implies, forces group members to flush their pending messages while blocking them to send any additional messages. The process of flushing acquiesces the group so that state transfer or a join can be done. It is also called stop-the-world model as nobody will be able to send messages while a flush is in process.
Flush is needed for:
(1) State transfer. When a member requests state transfer, the coordinator tells everyone to stop sending messages and waits for everyone's ack. Then it asks the application for its state and ships it back to the requester. After the requester has received and set the state successfully, the coordinator tells everyone to resume sending messages.
(2) View changes (e.g.a join). Before installing a new view V2, flushing would ensure that all messages *sent* in the current view V1 are indeed *delivered* in V1, rather than in V2 (in all non-faulty members). This is essentially Virtual Synchrony.
Nested Class Summary | |
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static class |
FLUSH.FlushHeader
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Field Summary | |
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static java.lang.String |
NAME
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Fields inherited from class org.jgroups.stack.Protocol |
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down_handler, down_prot, down_queue, down_thread, down_thread_prio, log, observer, props, stack, stats, up_handler, up_prot, up_queue, up_thread, up_thread_prio |
Constructor Summary | |
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FLUSH()
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Method Summary | |
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void |
down(Event evt)
An event is to be sent down the stack. |
double |
getAverageFlushDuration()
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java.lang.String |
getName()
|
int |
getNumberOfFlushes()
|
long |
getTotalTimeInFlush()
|
void |
init()
Called after instance has been created (null constructor) and before protocol is started. |
java.util.Vector |
providedDownServices()
List of events that are provided to layers below (they will be handled when sent down from below). |
boolean |
setProperties(java.util.Properties props)
Configures the protocol initially. |
void |
start()
This method is called on a Channel.connect(String) . |
boolean |
startFlush(long timeout)
|
void |
stop()
This method is called on a Channel.disconnect() . |
void |
stopFlush()
|
void |
up(Event evt)
An event was received from the layer below. |
Methods inherited from class org.jgroups.stack.Protocol |
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destroy, downThreadEnabled, dumpStats, enableStats, getDownProtocol, getDownQueue, getProperties, getUpProtocol, getUpQueue, handleSpecialDownEvent, passDown, passUp, printStats, providedUpServices, receiveDownEvent, receiveUpEvent, requiredDownServices, requiredUpServices, resetStats, setDownProtocol, setObserver, setPropertiesInternal, setProtocolStack, setUpProtocol, startDownHandler, startUpHandler, statsEnabled, stopInternal, upThreadEnabled |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
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public static final java.lang.String NAME
Constructor Detail |
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public FLUSH()
Method Detail |
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public java.lang.String getName()
getName
in class Protocol
public boolean setProperties(java.util.Properties props)
Protocol
"loopback=false;unicast_inport=4444"
setProperties
in class Protocol
public void init() throws java.lang.Exception
Protocol
init
in class Protocol
java.lang.Exception
- Thrown if protocol cannot be initialized successfully. This will cause the
ProtocolStack to fail, so the channel constructor will throw an exceptionpublic void start() throws java.lang.Exception
Protocol
Channel.connect(String)
. 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.
start
in class Protocol
java.lang.Exception
- Thrown if protocol cannot be started successfully. This will cause the ProtocolStack
to fail, so Channel.connect(String)
will throw an exceptionpublic void stop()
Protocol
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
stop
in class Protocol
public double getAverageFlushDuration()
public long getTotalTimeInFlush()
public int getNumberOfFlushes()
public boolean startFlush(long timeout)
public void stopFlush()
public void down(Event evt)
Protocol
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()
.
down
in class Protocol
public void up(Event evt)
Protocol
passDown()
or c) the event (or another event) is sent up
the stack using passUp()
.
up
in class Protocol
public java.util.Vector providedDownServices()
Protocol
providedDownServices
in class Protocol
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