org.jgroups.stack.MembershipChangePolicy Maven / Gradle / Ivy

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This artifact provides a single jar that contains all classes required to use remote EJB and JMS, including all dependencies. It is intended for use by those not using maven, maven users should just import the EJB and JMS BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up with different versions on classes on the class path).

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package org.jgroups.stack;

import org.jgroups.Address;

import java.util.Collection;
import java.util.List;

/**
 * Policy used to determine the new membership after a membership change (join, leave) or a merge. Can be installed in
 * {@link org.jgroups.protocols.pbcast.GMS} to override the default policy, which adds new members at the end on
 * a regular membership change, and adds all subviews into a new membership which is lexically sorted in case
 * of a merge.
 * @author Bela Ban
 * @since  3.4
 */
public interface MembershipChangePolicy {

    /**
     * Computes a new membership based on existing, joining, leaving and suspected members.
     * The first element of the new membership will be the coordinator.
     * @param current_members The list of current members. Guaranteed to be non-null (but may be empty)
     * @param joiners The joining members. Guaranteed to be non-null (but may be empty)
     * @param leavers Members that are leaving. Guaranteed to be non-null (but may be empty)
     * @param suspects Members which are suspected. Guaranteed to be non-null (but may be empty)
     * @return The new membership. The first element of the list is the (old or existing) coordinator.
     * There cannot be any duplicate members
     */
    List getNewMembership(final Collection current_members, final Collection joiners,
                                   final Collection leavers, final Collection suspects);

    /**
     * Compute a new membership based on a number of subviews
     * @param subviews A list of membership lists, e.g. [{A,B,C}, {M,N,O,P}, {X,Y,Z}]. This is a merge between
     *                 3 subviews. Guaranteed to be non-null (but may be empty)
     * @return The new membership. The first element of the list is the (old or existing) coordinator.
     * There cannot be any duplicate members
     */
    List getNewMembership(final Collection> subviews);
}