Package org.jgroups.protocols.pbcast
Class FLUSH
- java.lang.Object
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- org.jgroups.stack.Protocol
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- org.jgroups.protocols.pbcast.FLUSH
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public class FLUSH extends Protocol
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.
- Since:
- 2.4
- Author:
- Vladimir Blagojevic
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Nested Class Summary
Nested Classes Modifier and Type Class Description static class
FLUSH.FlushHeader
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Field Summary
Fields Modifier and Type Field Description protected boolean
bypass
protected boolean
enable_reconciliation
protected long
end_flush_timeout
protected long
retry_timeout
protected long
start_flush_timeout
protected long
timeout
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Fields inherited from class org.jgroups.stack.Protocol
after_creation_hook, down_prot, ergonomics, id, log, stack, stats, up_prot
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Constructor Summary
Constructors Constructor Description FLUSH()
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description java.lang.Object
down(Event evt)
An event is to be sent down the stack.java.lang.Object
down(Message msg)
A message is sent down the stack.double
getAverageFlushDuration()
int
getNumberOfFlushes()
long
getRetryTimeout()
long
getStartFlushTimeout()
long
getTotalTimeInFlush()
protected static Buffer
marshal(java.util.Collection<? extends Address> participants, Digest digest)
protected static Digest
maxSeqnos(View view, java.util.List<Digest> digests)
Returns a digest which contains, for all members of view, the highest delivered and received seqno of all digestsjava.util.List<java.lang.Integer>
providedDownServices()
List of events that are provided to layers below (they will be handled when sent from down below)protected Tuple<java.util.Collection<? extends Address>,Digest>
readParticipantsAndDigest(byte[] buffer, int offset, int length)
protected static boolean
same(java.util.List<Digest> digests)
boolean
setBypass(boolean flag)
void
setRetryTimeout(long retry_timeout)
void
setStartFlushTimeout(long start_flush_timeout)
void
start()
This method is called on aJChannel.connect(String)
.void
startFlush()
void
stop()
This method is called on aJChannel.disconnect()
.void
stopFlush()
java.lang.Object
up(Event evt)
An event was received from the protocol below.java.lang.Object
up(Message msg)
A single message was received.void
up(MessageBatch batch)
Sends up a multiple messages in aMessageBatch
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Methods inherited from class org.jgroups.stack.Protocol
accept, afterCreationHook, destroy, enableStats, getConfigurableObjects, getDownProtocol, getDownServices, getId, getIdsAbove, getLevel, getLog, getName, getProtocolStack, getSocketFactory, getThreadFactory, getTransport, getUpProtocol, getUpServices, getValue, init, isErgonomics, level, parse, providedUpServices, requiredDownServices, requiredUpServices, resetStatistics, resetStats, setDownProtocol, setErgonomics, setId, setLevel, setProtocolStack, setSocketFactory, setUpProtocol, setValue, statsEnabled
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Method Detail
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getStartFlushTimeout
public long getStartFlushTimeout()
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setStartFlushTimeout
public void setStartFlushTimeout(long start_flush_timeout)
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getRetryTimeout
public long getRetryTimeout()
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setRetryTimeout
public void setRetryTimeout(long retry_timeout)
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start
public void start() throws java.lang.Exception
Description copied from class:Protocol
This method is called on aJChannel.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.- Overrides:
start
in classProtocol
- Throws:
java.lang.Exception
- Thrown if protocol cannot be started successfully. This will cause the ProtocolStack to fail, soJChannel.connect(String)
will throw an exception
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stop
public void stop()
Description copied from class:Protocol
This method is called on aJChannel.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
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getAverageFlushDuration
public double getAverageFlushDuration()
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getTotalTimeInFlush
public long getTotalTimeInFlush()
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getNumberOfFlushes
public int getNumberOfFlushes()
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setBypass
public boolean setBypass(boolean flag)
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startFlush
public void startFlush()
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stopFlush
public void stopFlush()
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down
public java.lang.Object down(Event evt)
Description copied from class:Protocol
An event is to be sent down the stack. A protocol 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 protocol may need to add a header to it (or do nothing at all) before sending it down the stack usingdown_prot.down()
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down
public java.lang.Object down(Message msg)
Description copied from class:Protocol
A message is sent down the stack. Protocols may examine the message and do something (e.g. add a header) with it before passing it down.
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up
public java.lang.Object up(Event evt)
Description copied from class:Protocol
An event was received from the protocol below. Usually the current protocol 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 usingdown_prot.down()
or c) the event (or another event) is sent up the stack usingup_prot.up()
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up
public java.lang.Object up(Message msg)
Description copied from class:Protocol
A single message was received. Protocols may examine the message and do something (e.g. add a header) with it before passing it up.
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up
public void up(MessageBatch batch)
Description copied from class:Protocol
Sends up a multiple messages in aMessageBatch
. The sender of the batch is always the same, and so is the destination (null == multicast messages). Messages in a batch can be OOB messages, regular messages, or mixed messages, although the transport itself will create initial MessageBatches that contain only either OOB or regular messages. The default processing below sends messages up the stack individually, based on a matching criteria (callingProtocol.accept(org.jgroups.Message)
), and - if true - callsProtocol.up(org.jgroups.Event)
for that message and removes the message. If the batch is not empty, it is passed up, or else it is dropped. Subclasses should check if there are any messages destined for them (e.g. usingMessageBatch.getMatchingMessages(short,boolean)
), then possibly remove and process them and finally pass the batch up to the next protocol. Protocols can also modify messages in place, e.g. ENCRYPT could decrypt all encrypted messages in the batch, not remove them, and pass the batch up when done.
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providedDownServices
public java.util.List<java.lang.Integer> providedDownServices()
Description copied from class:Protocol
List of events that are provided to layers below (they will be handled when sent from down below)- Overrides:
providedDownServices
in classProtocol
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same
protected static boolean same(java.util.List<Digest> digests)
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maxSeqnos
protected static Digest maxSeqnos(View view, java.util.List<Digest> digests)
Returns a digest which contains, for all members of view, the highest delivered and received seqno of all digests
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marshal
protected static Buffer marshal(java.util.Collection<? extends Address> participants, Digest digest)
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