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java.lang.Objectorg.javagroups.stack.Protocol
org.javagroups.protocols.FD
Failure detection based on simple heartbeat protocol. Regularly polls members for liveness. Multicasts SUSPECT messages when a member is not reachable. The simple algorithms works as follows: the membership is known and ordered. Each HB protocol periodically sends an 'are-you-alive' message to its *neighbor*. A neighbor is the next in rank in the membership list, which is recomputed upon a view change. When a response hasn't been received for n milliseconds and m tries, the corresponding member is suspected (and eventually excluded if faulty).
FD starts when it detects (in a view change notification) that there are at least 2 members in the group. It stops running when the membership drops below 2.
When a message is received from the monitored neighbor member, it causes the pinger thread to 'skip' sending the next are-you-alive message. Thus, traffic is reduced.
When we receive a ping from a member that's not in the membership list, we shun it by sending it a
NOT_MEMBER message. That member will then leave the group (and possibly rejoin). This is only done if
shun
is true.
Nested Class Summary | |
static class |
FD.FdHeader
|
Field Summary |
Fields inherited from class org.javagroups.stack.Protocol |
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 | |
FD()
|
Method Summary | |
void |
down(Event evt)
An event is to be sent down the stack. |
java.lang.String |
getName()
|
void |
init()
Called after instance has been created (null constructor) and before protocol is started. |
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 |
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 |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
public FD()
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
|
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