Package org.jgroups.stack
Class Protocol
java.lang.Object
org.jgroups.stack.Protocol
- Direct Known Subclasses:
AUTH
,AUTOCONF
,BARRIER
,BSH
,CAUSAL
,COMPRESS
,DELAY
,DELAY_JOIN_REQ
,DISCARD
,DISCARD_PAYLOAD
,Discovery
,DUMMY_TP
,DUPL
,ENCRYPT
,EXAMPLE
,FC
,FD
,FD_ALL
,FD_SIMPLE
,FD_SOCK
,FLUSH
,FRAG
,FRAG2
,GMS
,HDRS
,HTOTAL
,JMS
,MERGE2
,MERGE3
,MERGEFAST
,NAKACK
,PARTITION
,PERF_TP
,ProtocolStack
,SEQUENCER
,SFC
,SHUFFLE
,SIZE
,SMACK
,STABLE
,STATE_TRANSFER
,STATS
,STREAMING_STATE_TRANSFER
,TP
,TP.ProtocolAdapter
,TRACE
,UNICAST
,VERIFY_SUSPECT
,VIEW_SYNC
The Protocol class provides a set of common services for protocol layers. Each layer has to
be a subclass of Protocol and override a number of methods (typically just
up()
,
down()
and getName()
. Layers are stacked in a certain order to form
a protocol stack. Events are passed from lower
layers to upper ones and vice versa. E.g. a Message received by the UDP layer at the bottom
will be passed to its higher layer as an Event. That layer will in turn pass the Event to
its layer and so on, until a layer handles the Message and sends a response or discards it,
the former resulting in another Event being passed down the stack.
The important thing to bear in mind is that Events have to passed on between layers in FIFO
order which is guaranteed by the Protocol implementation and must be guranteed by subclasses
implementing their on Event queuing.Note that each class implementing interface Protocol MUST provide an empty, public constructor !
- Version:
- $Id: Protocol.java,v 1.54.2.1 2008/05/22 13:23:04 belaban Exp $
- Author:
- Bela Ban
-
Field Summary
FieldsModifier and TypeFieldDescriptionprotected Protocol
protected final org.apache.commons.logging.Log
protected final Properties
protected ProtocolStack
protected boolean
protected Protocol
-
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionvoid
destroy()
This method is called on aChannel.close()
.An event is to be sent down the stack.boolean
Deprecated.down thread was removedvoid
enableStats
(boolean flag) abstract String
getName()
Supposed to be overwritten by subclasses.protected TP
void
init()
Called after instance has been created (null constructor) and before protocol is started.List of events that are provided to layers below (they will be handled when sent down from below).List of events that are provided to layers above (they will be handled when sent down from above).List of events that are required to be answered by some layer below.List of events that are required to be answered by some layer above.void
void
setDownProtocol
(Protocol down_prot) boolean
setProperties
(Properties props) Configures the protocol initially.boolean
setPropertiesInternal
(Properties props) Called by Configurator.void
setProtocolStack
(ProtocolStack stack) void
setUpProtocol
(Protocol up_prot) void
start()
This method is called on aChannel.connect(String)
.boolean
void
stop()
This method is called on aChannel.disconnect()
.An event was received from the layer below.boolean
Deprecated.up_thread was removed
-
Field Details
-
props
-
up_prot
-
down_prot
-
stack
-
stats
protected boolean stats -
log
protected final org.apache.commons.logging.Log log
-
-
Constructor Details
-
Protocol
public Protocol()
-
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Method Details
-
setProperties
Configures the protocol initially. A configuration string consists of name=value items, separated by a ';' (semicolon), e.g.:"loopback=false;unicast_inport=4444"
-
setPropertiesInternal
Called by Configurator. Removes 2 properties which are used by the Protocol directly and then calls setProperties(), which might invoke the setProperties() method of the actual protocol instance. -
getProperties
-
getProtocolStack
-
getTransport
-
getThreadFactory
Supposed to be overwritten by subclasses. Usually the transport returns a valid non-null thread factory, but thread factories can also be created by individual protocols- Returns:
-
upThreadEnabled
public boolean upThreadEnabled()Deprecated.up_thread was removed- Returns:
- false by default
-
downThreadEnabled
public boolean downThreadEnabled()Deprecated.down thread was removed- Returns:
- boolean False by default
-
statsEnabled
public boolean statsEnabled() -
enableStats
public void enableStats(boolean flag) -
resetStats
public void resetStats() -
printStats
-
dumpStats
-
init
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.- Throws:
Exception
- Thrown if protocol cannot be initialized successfully. This will cause the ProtocolStack to fail, so the channel constructor will throw an exception
-
start
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.- Throws:
Exception
- Thrown if protocol cannot be started successfully. This will cause the ProtocolStack to fail, soChannel.connect(String)
will throw an exception
-
stop
public void stop()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 -
destroy
public void destroy()This method is called on aChannel.close()
. Does some cleanup; after the call the VM will terminate -
requiredUpServices
List of events that are required to be answered by some layer above.- Returns:
- Vector (of Integers)
-
requiredDownServices
List of events that are required to be answered by some layer below.- Returns:
- Vector (of Integers)
-
providedUpServices
List of events that are provided to layers above (they will be handled when sent down from above).- Returns:
- Vector (of Integers)
-
providedDownServices
List of events that are provided to layers below (they will be handled when sent down from below).- Returns:
- Vectorinvalid input: '<'Integer (of Integers)
-
getName
-
getUpProtocol
-
getDownProtocol
-
setUpProtocol
-
setDownProtocol
-
setProtocolStack
-
up
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()
. -
down
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()
.
-