Class STREAMING_STATE_TRANSFER
STREAMING_STATE_TRANSFER
, as its name implies, allows a
streaming state transfer between two channel instances.
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. Application state, for example, might be located entirely
on some form of disk based storage. The default STATE_TRANSFER
requires this state to be loaded entirely into memory before being
transferred to a group member while STREAMING_STATE_TRANSFER
does not. Thus STREAMING_STATE_TRANSFER
protocol is able to
transfer application state that is very large (>1Gb) without a likelihood of
such transfer resulting in OutOfMemoryException.
Channel instance can be configured with either
In order to process streaming state transfer an application has to implement
STREAMING_STATE_TRANSFER
allows use of either default channel
transport or separate tcp sockets for state transfer. If firewalls are not a
concern then separate tcp sockets should be used as they offer faster state
transfer. Transport for state transfer is selected using
use_default_transport
boolean property.
STREAMING_STATE_TRANSFER
or STATE_TRANSFER
but not
both protocols at the same time.
ExtendedMessageListener
if it is using channel in a push style
mode or it has to process StreamingSetStateEvent
and
StreamingGetStateEvent
if it is using channel in a pull style
mode.
- Since:
- 2.4
- Version:
- $Id$
- Author:
- Vladimir Blagojevic
- See Also:
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Nested Class Summary
Nested Classes -
Field Summary
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionAn event is to be sent down the stack.double
final String
getName()
long
int
void
init()
Called after instance has been created (null constructor) and before protocol is started.List of events that are required to be answered by some layer below.void
boolean
setProperties
(Properties props) Configures the protocol initially.void
start()
This method is called on aChannel.connect(String)
.void
stop()
This method is called on aChannel.disconnect()
.An event was received from the layer below.Methods inherited from class org.jgroups.stack.Protocol
destroy, downThreadEnabled, dumpStats, enableStats, getDownProtocol, getProperties, getProtocolStack, getThreadFactory, getTransport, getUpProtocol, printStats, providedDownServices, providedUpServices, requiredUpServices, setDownProtocol, setPropertiesInternal, setProtocolStack, setUpProtocol, statsEnabled, upThreadEnabled
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Constructor Details
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STREAMING_STATE_TRANSFER
public STREAMING_STATE_TRANSFER()
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Method Details
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getName
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getNumberOfStateRequests
public int getNumberOfStateRequests() -
getNumberOfStateBytesSent
public long getNumberOfStateBytesSent() -
getAverageStateSize
public double getAverageStateSize() -
requiredDownServices
Description copied from class:Protocol
List of events that are required to be answered by some layer below.- Overrides:
requiredDownServices
in classProtocol
- Returns:
- Vector (of Integers)
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resetStats
public void resetStats()- Overrides:
resetStats
in classProtocol
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setProperties
Description copied from class:Protocol
Configures the protocol initially. A configuration string consists of name=value items, separated by a ';' (semicolon), e.g.:"loopback=false;unicast_inport=4444"
- Overrides:
setProperties
in classProtocol
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init
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. -
start
Description copied from class:Protocol
This method is called on aChannel.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:
Exception
- Thrown if protocol cannot be started successfully. This will cause the ProtocolStack to fail, soChannel.connect(String)
will throw an exception
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stop
public void stop()Description copied from class:Protocol
This method is called on aChannel.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 -
up
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 usingdown_prot.down()
or c) the event (or another event) is sent up the stack usingup_prot.up()
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down
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 usingdown_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 usingup_prot.up()
.
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