Package org.jgroups.protocols

Class FD

  • Direct Known Subclasses:
    FD_ICMP, FD_PING
    public class FD
extends Protocol
    Failure detection based on simple heartbeat protocol. Regularly polls members for liveness. Multicasts SUSPECT messages when a member is not reachable. The simple algorithms works as follows: the membership is known and ordered. Each HB protocol periodically sends an 'are-you-alive' message to its *neighbor*. A neighbor is the next in rank in the membership list, which 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.

    Version:
    $Id: FD.java,v 1.58.2.3 2008/05/22 13:23:06 belaban Exp $
    Author:
    Bela Ban

    • Field Detail

      • lock

        protected final java.util.concurrent.locks.Lock lock

      • num_heartbeats

        protected int num_heartbeats

      • num_suspect_events

        protected int num_suspect_events

      • bcast_task

        protected final FD.Broadcaster bcast_task
        Transmits SUSPECT message until view change or UNSUSPECT is received

    • Constructor Detail

      • FD

        public FD()

    • Method Detail

      • getName

        public java.lang.String getName()
        Specified by:
        getName in class Protocol

      • getLocalAddress

        public java.lang.String getLocalAddress()

      • getMembers

        public java.lang.String getMembers()

      • getPingableMembers

        public java.lang.String getPingableMembers()

      • getPingDest

        public java.lang.String getPingDest()

      • getNumberOfHeartbeatsSent

        public int getNumberOfHeartbeatsSent()

      • getNumSuspectEventsGenerated

        public int getNumSuspectEventsGenerated()

      • getTimeout

        public long getTimeout()

      • setTimeout

        public void setTimeout​(long timeout)

      • getMaxTries

        public int getMaxTries()

      • setMaxTries

        public void setMaxTries​(int max_tries)

      • getCurrentNumTries

        public int getCurrentNumTries()

      • isShun

        public boolean isShun()

      • setShun

        public void setShun​(boolean flag)

      • printSuspectHistory

        public java.lang.String printSuspectHistory()

      • 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. Properties are already set. Other protocols are not yet connected and events cannot yet be sent.
        Overrides:
        init in class Protocol
        Throws:
        java.lang.Exception - Thrown if protocol cannot be initialized successfully. This will cause the ProtocolStack to fail, so the channel constructor 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

      • 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 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 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 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