Package org.jgroups.blocks

Class NotificationBus

  • All Implemented Interfaces:
    MembershipListener, MessageListener, Receiver
    public class NotificationBus
extends java.lang.Object
implements Receiver
    This class provides notification sending and handling capability. Producers can send notifications to all registered consumers. Provides hooks to implement shared group state, which allows an application programmer to maintain a local cache which is replicated by all instances. NotificationBus sits on top of a channel, however it creates its channel itself, so the application programmers do not have to provide their own channel.
    Author:
    Bela Ban

    • Field Summary

      Fields 
      Modifier and Type Field Description
      protected org.apache.commons.logging.Log log  

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void block()
      Called (usually by the FLUSH protocol), as an indication that the member should stop sending messages.
      java.io.Serializable getCache()  
      java.io.Serializable getCacheFromCoordinator​(long timeout, int max_tries)
      Determines the coordinator and asks it for its cache.
      java.io.Serializable getCacheFromMember​(Address mbr, long timeout, int max_tries)
      Determines the coordinator and asks it for its cache.
      Channel getChannel()
      Answers the Channel.
      Address getLocalAddress()  
      java.util.Vector getMembership()
      Returns a reference to the real membership: don't modify.
      byte[] getState()
      Answers the group state; e.g., when joining.
      boolean isCoordinator()  
      void notifyConsumer​(java.io.Serializable n)
      Don't multicast this to all members, just apply it to local consumers.
      void receive​(Message msg)
      Called when a message is received.
      void sendNotification​(java.io.Serializable n)
      Pack the argument in a Info, serialize that one into the message buffer and send the message
      void sendNotification​(Address dest, java.io.Serializable n)
      Pack the argument in a Info, serialize that one into the message buffer and send the message
      void setConsumer​(NotificationBus.Consumer c)  
      void setState​(byte[] state)
      Sets the group state; e.g., when joining.
      void start()  
      void stop()  
      void suspect​(Address suspected_mbr)
      Called whenever a member is suspected of having crashed, but has not yet been excluded.
      void viewAccepted​(View new_view)
      Called when a change in membership has occurred.

      • Methods inherited from class java.lang.Object

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

    • Field Detail

      • log

        protected final org.apache.commons.logging.Log log

    • Constructor Detail

      • NotificationBus

        public NotificationBus()
                throws java.lang.Exception
        Throws:
        java.lang.Exception

      • NotificationBus

        public NotificationBus​(java.lang.String bus_name)
                throws java.lang.Exception
        Throws:
        java.lang.Exception

      • NotificationBus

        public NotificationBus​(java.lang.String bus_name,
                       java.lang.String properties)
                throws java.lang.Exception
        Throws:
        java.lang.Exception

      • NotificationBus

        public NotificationBus​(Channel channel,
                       java.lang.String bus_name)
                throws java.lang.Exception
        Throws:
        java.lang.Exception

    • Method Detail

      • getLocalAddress

        public Address getLocalAddress()

      • getMembership

        public java.util.Vector getMembership()
        Returns a reference to the real membership: don't modify. If you need to modify, make a copy first !
        Returns:
        Vector of Address objects

      • getChannel

        public Channel getChannel()
        Answers the Channel. Used to operate on the underlying channel directly, e.g. perform operations that are not provided using only NotificationBus. Should be used sparingly.
        Returns:
        underlying Channel

      • isCoordinator

        public boolean isCoordinator()

      • start

        public void start()
           throws java.lang.Exception
        Throws:
        java.lang.Exception

      • stop

        public void stop()

      • sendNotification

        public void sendNotification​(java.io.Serializable n)
        Pack the argument in a Info, serialize that one into the message buffer and send the message

      • sendNotification

        public void sendNotification​(Address dest,
                             java.io.Serializable n)
        Pack the argument in a Info, serialize that one into the message buffer and send the message

      • getCacheFromCoordinator

        public java.io.Serializable getCacheFromCoordinator​(long timeout,
                                                    int max_tries)
        Determines the coordinator and asks it for its cache. If there is no coordinator (because we are first member), null will be returned. Used only internally by NotificationBus.
        Parameters:
        timeout - Max number of msecs until the call returns
        max_tries - Max number of attempts to fetch the cache from the coordinator

      • getCacheFromMember

        public java.io.Serializable getCacheFromMember​(Address mbr,
                                               long timeout,
                                               int max_tries)
        Determines the coordinator and asks it for its cache. If there is no coordinator (because we are first member), null will be returned. Used only internally by NotificationBus.
        Parameters:
        mbr - The address of the member from which to fetch the state. If null, the current coordinator will be asked for the state
        timeout - Max number of msecs until the call returns - if timeout elapses null will be returned
        max_tries - Max number of attempts to fetch the cache from the coordinator (will be set to 1 if < 1)

      • notifyConsumer

        public void notifyConsumer​(java.io.Serializable n)
        Don't multicast this to all members, just apply it to local consumers.

      • getState

        public byte[] getState()
        Description copied from interface: MessageListener
        Answers the group state; e.g., when joining.
        Specified by:
        getState in interface MessageListener
        Returns:
        byte[]

      • setState

        public void setState​(byte[] state)
        Description copied from interface: MessageListener
        Sets the group state; e.g., when joining.
        Specified by:
        setState in interface MessageListener

      • viewAccepted

        public void viewAccepted​(View new_view)
        Description copied from interface: MembershipListener
        Called when a change in membership has occurred. No long running actions or sending of messages should be done in this callback. If some long running action needs to be performed, it should be done in a separate thread.

        Note that on reception of the first view (a new member just joined), the channel will not yet be in the connected state. This only happens when Channel.connect(String) returns.

        Specified by:
        viewAccepted in interface MembershipListener

      • suspect

        public void suspect​(Address suspected_mbr)
        Description copied from interface: MembershipListener
        Called whenever a member is suspected of having crashed, but has not yet been excluded.
        Specified by:
        suspect in interface MembershipListener

      • block

        public void block()
        Description copied from interface: MembershipListener
        Called (usually by the FLUSH protocol), as an indication that the member should stop sending messages. Any messages sent after returning from this callback might get blocked by the FLUSH protocol. When the FLUSH protocol is done, and messages can be sent again, the FLUSH protocol will simply unblock all pending messages. If a callback for unblocking is desired, implement ExtendedMembershipListener.unblock(). Note that block() is the equivalent of reception of a BlockEvent in the pull mode.
        Specified by:
        block in interface MembershipListener

      • getCache

        public java.io.Serializable getCache()