Package org.jgroups.protocols
Class FD_SOCK
- java.lang.Object
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- org.jgroups.stack.Protocol
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- org.jgroups.protocols.FD_SOCK
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- 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 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.
- Version:
- $Id: FD_SOCK.java,v 1.83.2.7 2009/02/05 16:22:00 vlada Exp $
- Author:
- Bela Ban May 29 2001
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Nested Class Summary
Nested Classes Modifier and Type Class Description static class
FD_SOCK.FdHeader
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Constructor Summary
Constructors Constructor Description FD_SOCK()
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description java.lang.Object
down(Event evt)
An event is to be sent down the stack.java.lang.String
getLocalAddress()
java.lang.String
getMembers()
java.lang.String
getName()
int
getNumSuspectEventsGenerated()
java.lang.String
getPingableMembers()
java.lang.String
getPingDest()
void
init()
Called after instance has been created (null constructor) and before protocol is started.java.lang.String
printCache()
java.lang.String
printSuspectHistory()
void
resetStats()
void
run()
Runs as long as there are 2 members and more.boolean
setProperties(java.util.Properties props)
Configures the protocol initially.void
start()
This method is called on aChannel.connect(String)
.void
stop()
This method is called on aChannel.disconnect()
.java.lang.Object
up(Event evt)
An event was received from the layer below.-
Methods inherited from class org.jgroups.stack.Protocol
destroy, downThreadEnabled, dumpStats, enableStats, getDownProtocol, getProperties, getProtocolStack, getThreadFactory, getTransport, getUpProtocol, printStats, providedDownServices, providedUpServices, requiredDownServices, requiredUpServices, setDownProtocol, setPropertiesInternal, setProtocolStack, setUpProtocol, statsEnabled, upThreadEnabled
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Method Detail
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getLocalAddress
public java.lang.String getLocalAddress()
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getMembers
public java.lang.String getMembers()
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getPingableMembers
public java.lang.String getPingableMembers()
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getPingDest
public java.lang.String getPingDest()
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getNumSuspectEventsGenerated
public int getNumSuspectEventsGenerated()
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printSuspectHistory
public java.lang.String printSuspectHistory()
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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 classProtocol
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printCache
public java.lang.String printCache()
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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. Properties are already set. Other protocols are not yet connected and events cannot yet be sent.
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start
public void start() throws java.lang.Exception
Description copied from class:Protocol
This method is called on aChannel.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 classProtocol
- Throws:
java.lang.Exception
- Thrown if protocol cannot be started successfully. This will cause the ProtocolStack to fail, soChannel.connect(String)
will throw an exception
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stop
public void stop()
Description copied from class:Protocol
This method is called on aChannel.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
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resetStats
public void resetStats()
- Overrides:
resetStats
in classProtocol
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up
public java.lang.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 usingdown_prot.down()
or c) the event (or another event) is sent up the stack usingup_prot.up()
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down
public java.lang.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 usingdown_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 usingup_prot.up()
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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 interfacejava.lang.Runnable
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