org.jgroups.protocols

Class BARRIER

java.lang.Object

org.jgroups.stack.Protocol

org.jgroups.protocols.BARRIER

public class BARRIER
extends Protocol

All messages up the stack have to go through a barrier (read lock, RL). By default, the barrier is open. When a CLOSE_BARRIER event is received, we close the barrier by acquiring a write lock (WL). This succeeds when all previous messages have completed (by releasing their RLs). Thus, when we have acquired the WL, we know that there are no pending messages processed.
When an OPEN_BARRIER event is received, we simply open the barrier again and let all messages pass in the up direction. This is done by releasing the WL.

Author:

Bela Ban

Field Summary

Fields

Modifier and Type	Field and Description
protected java.util.concurrent.atomic.AtomicBoolean	barrier_closed
protected java.util.concurrent.Future<?>	barrier_opener_future
protected long	flush_timeout
protected java.util.Set<Address>	holes
protected java.util.Map<java.lang.Thread,java.lang.Object>	in_flight_threads
protected Address	local_addr
protected java.util.concurrent.locks.Lock	lock
protected long	max_close_time
protected java.util.Map<Address,Message>	mcast_queue
protected java.util.concurrent.locks.Condition	no_pending_threads signals to waiting threads that the barrier is open again
protected static java.lang.Object	NULL
protected TimeScheduler	timer
protected TP	transport
protected java.util.Map<Address,Message>	ucast_queue

Fields inherited from class org.jgroups.stack.Protocol

after_creation_hook, down_prot, ergonomics, id, log, name, stack, stats, up_prot

Constructor Summary

Constructors

Constructor and Description
BARRIER()

Method Summary

Modifier and Type	Method and Description
protected void	cancelBarrierOpener()
void	closeBarrier() Close the barrier.
void	destroy() This method is called on a Channel.close().
java.lang.Object	down(Event evt) An event is to be sent down the stack.
protected void	flushQueue(java.util.Map<Address,Message> queue)
java.lang.String	getHoles()
int	getInFlightThreadsCount()
int	getNumberOfInFlightThreads()
void	init() Called after instance has been created (null constructor) and before protocol is started.
boolean	isClosed()
boolean	isOpenerScheduled()
void	openBarrier()
protected java.lang.String	printInFlightThreads()
protected void	scheduleBarrierOpener()
void	stop() This method is called on a Channel.disconnect().
protected void	unblock(java.lang.Thread current_thread)
java.lang.Object	up(Event evt) An event was received from the layer below.
void	up(MessageBatch batch) Sends up a multiple messages in a MessageBatch.

Methods inherited from class org.jgroups.stack.Protocol

accept, afterCreationHook, dumpStats, enableStats, getConfigurableObjects, getDownProtocol, getDownServices, getId, getIdsAbove, getLevel, getLog, getName, getProtocolStack, getSocketFactory, getThreadFactory, getTransport, getUpProtocol, getUpServices, getValue, isErgonomics, level, parse, printStats, providedDownServices, providedUpServices, requiredDownServices, requiredUpServices, resetStatistics, resetStats, setDownProtocol, setErgonomics, setId, setLevel, setProtocolStack, setSocketFactory, setUpProtocol, setValue, setValues, start, statsEnabled

Methods inherited from class java.lang.Object

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

Field Detail

max_close_time

protected long max_close_time

flush_timeout

protected long flush_timeout

lock

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

barrier_closed

protected final java.util.concurrent.atomic.AtomicBoolean barrier_closed

no_pending_threads

protected java.util.concurrent.locks.Condition no_pending_threads

signals to waiting threads that the barrier is open again

in_flight_threads

protected java.util.Map<java.lang.Thread,java.lang.Object> in_flight_threads

barrier_opener_future

protected volatile java.util.concurrent.Future<?> barrier_opener_future

timer

protected TimeScheduler timer

local_addr

protected Address local_addr

holes

protected final java.util.Set<Address> holes

mcast_queue

protected final java.util.Map<Address,Message> mcast_queue

ucast_queue

protected final java.util.Map<Address,Message> ucast_queue

transport

protected TP transport

NULL

protected static final java.lang.Object NULL

Constructor Detail

BARRIER

public BARRIER()

Method Detail

isClosed

public boolean isClosed()

getHoles

public java.lang.String getHoles()

getNumberOfInFlightThreads

public int getNumberOfInFlightThreads()

getInFlightThreadsCount

public int getInFlightThreadsCount()

isOpenerScheduled

public boolean isOpenerScheduled()

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

destroy

public void destroy()

Description copied from class: Protocol

This method is called on a Channel.close(). Does some cleanup; after the call the VM will terminate

Overrides:

destroy 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

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

up

public void up(MessageBatch batch)

Description copied from class: Protocol

Sends up a multiple messages in a MessageBatch. 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 (calling Protocol.accept(org.jgroups.Message)), and - if true - calls Protocol.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. using MessageBatch.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.

Overrides:

up in class Protocol

Parameters:

batch - The message batch

unblock

protected void unblock(java.lang.Thread current_thread)

closeBarrier

public void closeBarrier()

Close the barrier. Temporarily remove all threads which are waiting or blocked, re-insert them after the call

openBarrier

public void openBarrier()

printInFlightThreads

protected java.lang.String printInFlightThreads()

flushQueue

protected void flushQueue(java.util.Map<Address,Message> queue)

scheduleBarrierOpener

protected void scheduleBarrierOpener()

cancelBarrierOpener

protected void cancelBarrierOpener()