org.javagroups.protocols
Class FD
java.lang.Object
|
+--org.javagroups.stack.Protocol
|
+--org.javagroups.protocols.FD
- public class FD
- extends Protocol
Failure detection based on simple heartbeat protocol. Regularly polls members for
liveness. Passes SUSPECT message up the stack when a member is not reachable. The simple
algorithms works as follows: the membership is known and ordered. Each HB protocol
periodically sends a 'are-you-alive' message to its *neighbor*. A neighbor is the next in
rank in the membership list. It 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.
- Author:
- Bela Ban
Fields inherited from class org.javagroups.stack.Protocol |
down_handler, down_prot, down_queue, down_thread, observer, props, stack, up_handler, up_prot, up_queue, up_thread |
Method Summary |
void |
down(Event evt)
An event is to be sent down the stack. |
java.lang.String |
getName()
|
boolean |
setProperties(java.util.Properties props)
Configures the protocol initially. |
void |
up(Event evt)
An event was received from the layer below. |
Methods inherited from class org.javagroups.stack.Protocol |
getDownProtocol, getDownQueue, getProperties, getUpProtocol, getUpQueue, init, passDown, passUp, providedDownServices, providedUpServices, receiveDownEvent, receiveUpEvent, requiredDownServices, requiredUpServices, setDownProtocol, setObserver, setPropertiesInternal, setProtocolStack, setUpProtocol, startDownHandler, startUpHandler, stopInternal |
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
FD
public FD()
getName
public java.lang.String getName()
- Overrides:
getName
in class Protocol
setProperties
public boolean setProperties(java.util.Properties props)
- 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 class Protocol
up
public void 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
passDown()
or c) the event (or another event) is sent up
the stack using passUp()
.
- Overrides:
up
in class Protocol
down
public void 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
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()
.
- Overrides:
down
in class Protocol
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