org.javagroups.protocols
Class FD_SOCK
java.lang.Object
|
+--org.javagroups.stack.Protocol
|
+--org.javagroups.protocols.FD_SOCK
- All Implemented Interfaces:
- java.lang.Runnable
- public class FD_SOCK
- extends Protocol
- implements java.lang.Runnable
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.
- Author:
- Bela Ban May 29 2001
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()
|
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 |
up(Event evt)
An event was received from the layer below. |
Methods inherited from class org.javagroups.stack.Protocol |
getDownProtocol, getDownQueue, getProperties, getUpProtocol, getUpQueue, 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_SOCK
public FD_SOCK()
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
init
public void init()
throws java.lang.Exception
- Description copied from class:
Protocol
- Called after instance has been created (null constructor) and before protocol is started
- Overrides:
init
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
run
public void run()
- Runs as long as there are 2 members and more. Determines the member to be monitored and fetches its
server socket address (if n/a, sends a message to obtain it). The creates a client socket and listens on
it until the connection breaks. If it breaks, emits a SUSPECT message. It the connection is closed regularly,
nothing happens. In both cases, a new member to be monitored will be chosen and monitoring continues (unless
there are fewer than 2 members).
- Specified by:
run
in interface java.lang.Runnable
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