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java.lang.Object | +--org.javagroups.stack.Protocol | +--org.javagroups.protocols.FD_SOCK
Failure detection protocol based on sockets. Failure detection is ring-based. Each member creates a server socket and announces its address together with the server socket's address in a multicast. A pinger thread will be started when the membership goes above 1 and will be stopped when it drops below 2. The pinger thread connects to its neighbor on the right and waits until the socket is closed. When the socket is closed by the monitored peer in an abnormal fashion (IOException), the neighbor will be suspected.
The main feature of this protocol is that no ping messages need to be exchanged between any 2 peers, and failure detection relies entirely on TCP sockets. The advantage is that no activity will take place between 2 peers as long as they are alive (i.e. have their server sockets open). The FD_SOCK protocol will work for groups where members are on different hosts, but its main usage is when all group members are on the same host.
The costs involved are 2 additional threads: one that monitors the client side of the socket connection (to monitor a peer) and another one that manages the server socket. However, those threads will be idle as long as both peers are running.
Nested Class Summary | |
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static class |
FD_SOCK.FdHeader
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Field Summary |
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Fields inherited from class org.javagroups.stack.Protocol |
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down_handler, down_prot, down_queue, down_thread, down_thread_prio, observer, props, stack, up_handler, up_prot, up_queue, up_thread, up_thread_prio |
Constructor Summary | |
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FD_SOCK()
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Method Summary | |
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void |
down(Event evt)
An event is to be sent down the stack. |
java.lang.String |
getName()
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void |
init()
Called after instance has been created (null constructor) and before protocol is started. |
void |
run()
Runs as long as there are 2 members and more. |
boolean |
setProperties(java.util.Properties props)
Configures the protocol initially. |
void |
stop()
This method is called on a Channel.disconnect() . |
void |
up(Event evt)
An event was received from the layer below. |
Methods inherited from class org.javagroups.stack.Protocol |
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destroy, getDownProtocol, getDownQueue, getProperties, getUpProtocol, getUpQueue, passDown, passUp, providedDownServices, providedUpServices, receiveDownEvent, receiveUpEvent, requiredDownServices, requiredUpServices, setDownProtocol, setObserver, setPropertiesInternal, setProtocolStack, setUpProtocol, start, startDownHandler, startUpHandler, stopInternal |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
public FD_SOCK()
Method Detail |
public java.lang.String getName()
getName
in class Protocol
public boolean setProperties(java.util.Properties props)
Protocol
"loopback=false;unicast_inport=4444"
setProperties
in class Protocol
public void init() throws java.lang.Exception
Protocol
init
in class Protocol
java.lang.Exception
- Thrown if protocol cannot be initialized successfully. This will cause the
ProtocolStack to fail, so the channel constructor will throw an exceptionpublic void stop()
Protocol
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
stop
in class Protocol
public void up(Event evt)
Protocol
passDown()
or c) the event (or another event) is sent up
the stack using passUp()
.
up
in class Protocol
public void down(Event evt)
Protocol
passDown()
. 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 passUp()
.
down
in class Protocol
public void run()
run
in interface java.lang.Runnable
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