Package org.eclipse.persistence.sessions.coordination

Class DiscoveryManager

java.lang.Object
org.eclipse.persistence.sessions.coordination.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.

See Also:
Author:
Steven Vo

  • Field Details

    • DEFAULT_MULTICAST_GROUP

      public static final String DEFAULT_MULTICAST_GROUP
      Default value constants
      See Also:

    • DEFAULT_MULTICAST_PORT

      public static final int DEFAULT_MULTICAST_PORT
      See Also:

    • DEFAULT_PACKET_TIME_TO_LIVE

      public static final int DEFAULT_PACKET_TIME_TO_LIVE
      See Also:

    • DEFAULT_ANNOUNCEMENT_DELAY

      public static final int DEFAULT_ANNOUNCEMENT_DELAY
      See Also:

    • 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

    • rcm

      protected RemoteCommandManager rcm
      The remote command manager responsible for this service

  • Constructor Details

  • Method Details

    • 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.