org.javagroups.protocols
Class FD_PID
java.lang.Object
|
+--org.javagroups.stack.Protocol
|
+--org.javagroups.protocols.FD_PID
- public class FD_PID
- extends Protocol
Process-ID based FD protocol. The existence of a process will be tested
via the process ID instead of message based pinging. In order to probe a process' existence, the application (or
some other protocol layer) has to send down a SET_PID event for the member. The addresses of all members will
be associated with their respective PIDs. The PID will be used to probe for the existence of that process.
A cache of Addresses and PIDs is maintained in each member, which is adjusted upon reception of view changes.
The population of the addr:pid cache is as follows:
When a new member joins, it requests the PID cache from the coordinator. Then it broadcasts its own addr:pid
association, so all members can update their cache. When a member P is to be pinged by Q, and Q doesn't have
P'd PID, Q will broadcast a WHO_HAS_PID message, to which all members who have that entry will respond. The
latter case should actually never happen because all members should always have consistent caches. However,
it is left in the code as a second line of defense.
Note that
1. The SET_PID has to be sent down after connecting to a channel !
2. Note that if a process is shunned and subsequently reconnects, the SET_PID event has to be resent !
3. This protocol only works for groups whose members are on the same host . 'Host' actually means the
same IP address (e.g. for multi-homed systems).
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_PID
public FD_PID()
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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