Package org.eclipse.persistence.sessions.coordination

Class DiscoveryManager

  • All Implemented Interfaces:
    Runnable
    public class DiscoveryManager
extends Object
implements Runnable

    Purpose: Detects new members of a logical EclipseLink cluster.

    Description: Each RemoteCommandManager has its own DiscoveryManager, which handles the detection of other remote command services as they become available. The DiscoveryManager is an active object (in that it extends Thread) and becomes a separate thread when it is started using startDiscovery().

    Discovery is done through the use of a multicast. Each discovery manager joins the multicast group and announces itself to the group. As it receives service announcements from other discovery managers it notifies the RCM to establish connections to and from the new service.

    Since:
    OracleAS TopLink 10g (9.0.4)
    Author:
    Steven Vo
    See Also:
    RemoteCommandManager, MulticastSocket

    • Field Detail

      • DEFAULT_PACKET_TIME_TO_LIVE

        public static final int DEFAULT_PACKET_TIME_TO_LIVE
        See Also:
        Constant Field Values

      • DEFAULT_ANNOUNCEMENT_DELAY

        public static final int DEFAULT_ANNOUNCEMENT_DELAY
        See Also:
        Constant Field Values

      • multicastGroupAddress

        protected String multicastGroupAddress
        Defines the IP address of the multicast group

      • multicastPort

        protected int multicastPort
        Defines the port the multicast socket will be using

      • communicationSocket

        protected MulticastSocket communicationSocket
        The multicast socket used for discovery

      • packetTimeToLive

        protected int packetTimeToLive
        Number of hops in the life of the datapacket Default is 2, a hub and an interface card to prevent the data packets from leaving the localnetwork.

      • stopListening

        protected boolean stopListening
        Indicates to the listening thread that it should stop

      • announcementDelay

        protected int announcementDelay
        Delay time in millis between initialization and when the announcement is sent

    • Method Detail

      • announceSession

        public void announceSession()
        INTERNAL: Send out an announcement that we are here.

      • startDiscovery

        public void startDiscovery()
        ADVANCED: Announce the local service and join the cluster

      • stopDiscovery

        public void stopDiscovery()
        ADVANCED: Stop accepting announcements from other services becoming available. Note that this does not remove the local service from the cluster.

      • isDiscoveryStopped

        public boolean isDiscoveryStopped()
        ADVANCED: Return true if discovery has been stopped at the time this method is called. If false is returned then it is undefined whether discovery is started or stopped. It may be started, or it may be in the process of starting or stopping.

      • createCommunicationSocket

        public void createCommunicationSocket()
        INTERNAL: Create the multicast socket and join the multicast group.

      • getCommunicationSocket

        public MulticastSocket getCommunicationSocket()
        INTERNAL: Return the socket that will be used for the multicast.

      • run

        public void run()
        INTERNAL: This is the main execution method of discovery. It will create a socket to listen on, create a local connection for this service and announce that we are open for business.
        Specified by:
        run in interface Runnable

      • startListening

        public void startListening()
        INTERNAL: This method puts us into the listening mode loop. This thread blocks, waiting on announcements that we receive from other discovery managers.

      • stopListening

        public void stopListening()
        INTERNAL: Signal this instance to stop listening.

      • receivedAnnouncement

        public void receivedAnnouncement​(ServiceId serviceId)
        INTERNAL: Process the announcement that indicates that a new service is online

      • setAnnouncementDelay

        public void setAnnouncementDelay​(int millisecondsToDelay)
        PUBLIC: Set the amount of time in millis that the service should wait between the time that this Remote Service is available and a session announcement is sent out to other discovery managers. This may be needed to give some systems more time to post their connections into the naming service. Takes effect the next time listening is started.

      • getAnnouncementDelay

        public int getAnnouncementDelay()
        PUBLIC: Return the amount of time in millis that the service should wait between the time that this Remote Service is available and a session announcement is sent out to other discovery managers.

      • getMulticastGroupAddress

        public String getMulticastGroupAddress()
        PUBLIC: Return the host address of the multicast group.

      • setMulticastGroupAddress

        public void setMulticastGroupAddress​(String address)
        PUBLIC: Set the host address of the multicast group. Takes effect the next time listening is started.

      • setMulticastPort

        public void setMulticastPort​(int port)
        PUBLIC: Set the multicast port used for discovery. Takes effect the next time listening is started.

      • getMulticastPort

        public int getMulticastPort()
        PUBLIC: Return the multicast port used for discovery.

      • shallowCopy

        protected void shallowCopy​(DiscoveryManager dmgr)
        INTERNAL: invoke when the RCM shutdown. Subclass overrides this method if necessary.

      • getPacketTimeToLive

        public int getPacketTimeToLive()
        PUBLIC: Returns the number of hops the data packets of the session announcement will take before expiring. The default is 2, a hub and an interface card to prevent the data packets from leaving the local network.

      • setPacketTimeToLive

        public void setPacketTimeToLive​(int newPacketTimeToLive)
        PUBLIC: Set the number of hops the data packets of the session announcement will take before expiring. The default is 2, a hub and an interface card to prevent the data packets from leaving the local network. Note that if sessions are hosted on different LANs that are part of WAN, the announcement sending by one session may not reach other sessions. In this case, consult your network administrator for the right time-to-live value or test your network by increase the value until sessions receive announcement sent by others.