org.jgroups.protocols.pbcast
Class StreamingStateTransfer

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

Direct Known Subclasses:

STATE, STATE_SOCK

public abstract class StreamingStateTransfer
extends Protocol

Base class for state transfer protocols which use streaming (or chunking) to transfer state between two members.

The major advantage of this approach is that transferring application state to a joining member of a group does not entail loading of the complete application state into memory. The application state, for example, might be located entirely on some form of disk based storage. The default STATE_TRANSFER protocol requires this state to be loaded entirely into memory before being transferred to a group member while the streaming state transfer protocols do not. Thus the streaming state transfer protocols are able to transfer application state that is very large (>1Gb) without a likelihood of the such transfer resulting in OutOfMemoryException.

Note that prior to 3.0, there was only 1 streaming protocol: STATE. In 3.0 the functionality was split between STATE and STATE_SOCK, and common functionality moved up into StreamingStateTransfer.

Since:

3.0

Author:

Bela Ban, Vladimir Blagojevic

See Also:

STATE_TRANSFER, STATE, STATE_SOCK

Nested Class Summary

protected class	StreamingStateTransfer.StateGetter Thread which invokes MessageListener.getState(java.io.OutputStream) in the application
static class	StreamingStateTransfer.StateHeader

Field Summary

protected double	avg_state_size
protected java.util.concurrent.atomic.AtomicBoolean	barrier_closed Used to prevent spurious open and close barrier calls
protected int	buffer_size
protected boolean	flushProtocolInStack
protected Address	local_addr
protected int	max_pool
protected java.util.List<Address>	members
protected java.util.concurrent.atomic.AtomicLong	num_bytes_sent
protected java.util.concurrent.atomic.AtomicInteger	num_state_reqs
protected java.util.Map<Address,java.io.OutputStream>	pending_state_transfers Whenever we get a state transfer request, we create an OutputStream and add the state requester's address and the OutputStream to this map.
protected long	pool_thread_keep_alive
protected java.util.concurrent.locks.Lock	state_lock Used to synchronize all state requests and responses
protected Address	state_provider
protected java.util.concurrent.ThreadPoolExecutor	thread_pool Thread pool (configured with max_pool and pool_thread_keep_alive) to run StreamingStateTransfer.StateGetter threads on

Fields inherited from class org.jgroups.stack.Protocol

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

Constructor Summary

StreamingStateTransfer()

Method Summary

void	closeBarrierAndSuspendStable()
protected abstract void	createStreamToProvider(Address provider, StreamingStateTransfer.StateHeader hdr) Creates an InputStream to the state provider to read the state
protected abstract void	createStreamToRequester(Address requester) Creates an OutputStream to the state requester to write the state
protected java.util.concurrent.ThreadPoolExecutor	createThreadPool()
void	destroy() This method is called on a Channel.close().
protected Address	determineCoordinator()
java.lang.Object	down(Event evt) An event is to be sent down the stack.
double	getAverageStateSize()
long	getNumberOfStateBytesSent()
int	getNumberOfStateRequests()
protected void	getStateFromApplication(Address requester, java.io.OutputStream out, boolean use_separate_thread)
long	getThreadPoolCompletedTasks()
int	getThreadPoolSize()
protected void	handleConfig(java.util.Map<java.lang.String,java.lang.Object> config)
protected void	handleEOF(Address sender)
protected void	handleException(java.lang.Throwable exception)
protected void	handleStateChunk(Address sender, byte[] buffer, int offset, int length)
protected void	handleStateReq(Address requester)
protected void	handleViewChange(View v)
void	init() Called after instance has been created (null constructor) and before protocol is started.
protected boolean	isDigestNeeded() When FLUSH is used we do not need to pass digests between members (see JGroups/doc/design/FLUSH.txt)
protected void	modifyStateResponseHeader(StreamingStateTransfer.StateHeader hdr)
void	openBarrierAndResumeStable()
protected void	removeRequester(Address requester)
java.util.List<java.lang.Integer>	requiredDownServices() List of events that are required to be answered by some layer below
void	resetStats()
protected void	sendEof(Address requester)
protected void	sendException(Address requester, java.lang.Throwable exception)
protected void	setStateInApplication(Address provider, java.io.InputStream in, Digest digest)
void	start() This method is called on a Channel.connect(String).
void	stop() This method is called on a Channel.disconnect().
java.lang.Object	up(Event evt) An event was received from the layer below.

Methods inherited from class org.jgroups.stack.Protocol

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

Methods inherited from class java.lang.Object

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

Field Detail

buffer_size

protected int buffer_size

max_pool

protected int max_pool

pool_thread_keep_alive

protected long pool_thread_keep_alive

num_state_reqs

protected final java.util.concurrent.atomic.AtomicInteger num_state_reqs

num_bytes_sent

protected final java.util.concurrent.atomic.AtomicLong num_bytes_sent

avg_state_size

protected double avg_state_size

local_addr

protected Address local_addr

state_provider

protected volatile Address state_provider

members

protected final java.util.List<Address> members

flushProtocolInStack

protected volatile boolean flushProtocolInStack

barrier_closed

protected java.util.concurrent.atomic.AtomicBoolean barrier_closed

Used to prevent spurious open and close barrier calls

thread_pool

protected java.util.concurrent.ThreadPoolExecutor thread_pool

Thread pool (configured with max_pool and pool_thread_keep_alive) to run StreamingStateTransfer.StateGetter threads on

pending_state_transfers

protected final java.util.Map<Address,java.io.OutputStream> pending_state_transfers

Whenever we get a state transfer request, we create an OutputStream and add the state requester's address and the OutputStream to this map. The state is fetched from the application on a separate thread, a StreamingStateTransfer.StateGetter thread.

state_lock

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

Used to synchronize all state requests and responses

Constructor Detail

StreamingStateTransfer

public StreamingStateTransfer()

Method Detail

getNumberOfStateRequests

public int getNumberOfStateRequests()

getNumberOfStateBytesSent

public long getNumberOfStateBytesSent()

getAverageStateSize

public double getAverageStateSize()

getThreadPoolSize

public int getThreadPoolSize()

getThreadPoolCompletedTasks

public long getThreadPoolCompletedTasks()

requiredDownServices

public java.util.List<java.lang.Integer> requiredDownServices()

Description copied from class: Protocol

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

Overrides:

requiredDownServices in class Protocol

resetStats

public void resetStats()

Overrides:

resetStats in class Protocol

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

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

start

public void start()
           throws java.lang.Exception

Description copied from class: Protocol

This method is called on a 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.

Overrides:

start in class Protocol

Throws:

java.lang.Exception - Thrown if protocol cannot be started successfully. This will cause the ProtocolStack to fail, so Channel.connect(String) 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

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

isDigestNeeded

protected boolean isDigestNeeded()

When FLUSH is used we do not need to pass digests between members (see JGroups/doc/design/FLUSH.txt)

Returns:

true if use of digests is required, false otherwise

handleConfig

protected void handleConfig(java.util.Map<java.lang.String,java.lang.Object> config)

handleStateChunk

protected void handleStateChunk(Address sender,
                                byte[] buffer,
                                int offset,
                                int length)

handleEOF

protected void handleEOF(Address sender)

handleException

protected void handleException(java.lang.Throwable exception)

getStateFromApplication

protected void getStateFromApplication(Address requester,
                                       java.io.OutputStream out,
                                       boolean use_separate_thread)

removeRequester

protected void removeRequester(Address requester)

setStateInApplication

protected void setStateInApplication(Address provider,
                                     java.io.InputStream in,
                                     Digest digest)

closeBarrierAndSuspendStable

public void closeBarrierAndSuspendStable()

openBarrierAndResumeStable

public void openBarrierAndResumeStable()

sendEof

protected void sendEof(Address requester)

sendException

protected void sendException(Address requester,
                             java.lang.Throwable exception)

createThreadPool

protected java.util.concurrent.ThreadPoolExecutor createThreadPool()

determineCoordinator

protected Address determineCoordinator()

handleViewChange

protected void handleViewChange(View v)

handleStateReq

protected void handleStateReq(Address requester)

createStreamToRequester

protected abstract void createStreamToRequester(Address requester)

Creates an OutputStream to the state requester to write the state

createStreamToProvider

protected abstract void createStreamToProvider(Address provider,
                                               StreamingStateTransfer.StateHeader hdr)

Creates an InputStream to the state provider to read the state

modifyStateResponseHeader

protected void modifyStateResponseHeader(StreamingStateTransfer.StateHeader hdr)