org.jgroups.protocols

Class FD_SOCK

java.lang.Object

org.jgroups.stack.Protocol

org.jgroups.protocols.FD_SOCK

All Implemented Interfaces:

Runnable

public class FD_SOCK
extends Protocol
implements 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 disadvantage is that hung servers or crashed routers will not cause sockets to be closed, therefore they won't be detected. The FD_SOCK protocol will work for groups where members are on different hosts

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

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	FD_SOCK.FdHeader

Field Summary

Fields

Modifier and Type	Field and Description
protected String	bind_interface_str
protected InetAddress	external_addr
protected int	external_port
protected Set<Address>	suspected_mbrs

Fields inherited from class org.jgroups.stack.Protocol

down_prot, ergonomics, id, log, name, stack, stats, up_prot

Constructor Summary

Constructors

Constructor and Description
FD_SOCK()

Method Summary

Methods

Modifier and Type	Method and Description
protected Address	determineCoordinator()
Object	down(Event evt) An event is to be sent down the stack.
String	getLocalAddress()
String	getMembers()
int	getNumSuspectEventsGenerated()
String	getPingableMembers()
String	getPingDest()
void	init() Called after instance has been created (null constructor) and before protocol is started.
boolean	isLogSuspectedMessages()
String	printCache()
String	printSuspectHistory()
void	resetStats()
void	run() Runs as long as there are 2 members and more.
void	setLogSuspectedMessages(boolean log_suspected_msgs)
void	start() This method is called on a Channel.connect(String).
void	stop() This method is called on a Channel.disconnect().
void	stopServerSocket(boolean graceful)
Object	up(Event evt) An event was received from the layer below.

Methods inherited from class org.jgroups.stack.Protocol

destroy, dumpStats, enableStats, getConfigurableObjects, getDownProtocol, getId, getLevel, getName, getProtocolStack, getSocketFactory, getThreadFactory, getTransport, getUpProtocol, getValue, isErgonomics, printStats, providedDownServices, providedUpServices, requiredDownServices, requiredUpServices, resetStatistics, setDownProtocol, setErgonomics, setId, setLevel, setProtocolStack, setSocketFactory, setUpProtocol, setValue, setValues, statsEnabled

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

external_addr

protected InetAddress external_addr

external_port

protected int external_port

bind_interface_str

protected String bind_interface_str

suspected_mbrs

protected final Set<Address> suspected_mbrs

Constructor Detail

FD_SOCK

public FD_SOCK()

Method Detail

getLocalAddress

public String getLocalAddress()

getMembers

public String getMembers()

getPingableMembers

public String getPingableMembers()

getPingDest

public String getPingDest()

getNumSuspectEventsGenerated

public int getNumSuspectEventsGenerated()

isLogSuspectedMessages

public boolean isLogSuspectedMessages()

setLogSuspectedMessages

public void setLogSuspectedMessages(boolean log_suspected_msgs)

printSuspectHistory

public String printSuspectHistory()

printCache

public String printCache()

init

public void init()
          throws Exception

Description copied from class: Protocol

Called after instance has been created (null constructor) and before protocol is started. Properties are already set. Other protocols are not yet connected and events cannot yet be sent.

Overrides:

init in class Protocol

Throws:

Exception - Thrown if protocol cannot be initialized successfully. This will cause the ProtocolStack to fail, so the channel constructor will throw an exception

start

public void start()
           throws Exception

Description copied from class: Protocol

This method is called on a Channel.connect(String). Starts work. Protocols are connected and queues are ready to receive events. Will be called from bottom to top. This call will replace the START and START_OK events.

Overrides:

start in class Protocol

Throws:

Exception - Thrown if protocol cannot be started successfully. This will cause the ProtocolStack to fail, so Channel.connect(String) will throw an exception

stop

public void stop()

Description copied from class: Protocol

This method is called on a 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

Overrides:

stop in class Protocol

resetStats

public void resetStats()

Overrides:

resetStats in class Protocol

up

public Object 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 down_prot.down() or c) the event (or another event) is sent up the stack using up_prot.up().

Overrides:

up in class Protocol

down

public Object 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 down_prot.down(). 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 up_prot.up().

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 Runnable

stopServerSocket

public void stopServerSocket(boolean graceful)

determineCoordinator

protected Address determineCoordinator()