bookkeeper-server/src/main/java/org/apache/bookkeeper/client/DistributionSchedule.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.bookkeeper.client;

import java.util.List;
/**
 * This interface determins how entries are distributed among bookies.
 *
 * Every entry gets replicated to some number of replicas. The first replica for
 * an entry is given a replicaIndex of 0, and so on. To distribute write load,
 * not all entries go to all bookies. Given an entry-id and replica index, an
 * {@link DistributionSchedule} determines which bookie that replica should go
 * to.
 */

interface DistributionSchedule {

    /**
     * return the set of bookie indices to send the message to
     */
    public List<Integer> getWriteSet(long entryId);

    /**
     * An ack set represents the set of bookies from which
     * a response must be received so that an entry can be
     * considered to be replicated on a quorum.
     */
    public interface AckSet {
        /**
         * Add a bookie response and check if quorum has been met
         * @return true if quorum has been met, false otherwise
         */
        public boolean addBookieAndCheck(int bookieIndexHeardFrom);

        /**
         * Invalidate a previous bookie response.
         * Used for reissuing write requests.
         */
        public void removeBookie(int bookie);
    }

    /**
     * Returns an ackset object, responses should be checked against this
     */
    public AckSet getAckSet();


    /**
     * Interface to keep track of which bookies in an ensemble, an action
     * has been performed for.
     */
    public interface QuorumCoverageSet {
        /**
         * Add a bookie to the set, and check if all quorum in the set
         * have had the action performed for it.
         * @param bookieIndexHeardFrom Bookie we've just heard from
         * @return whether all quorums have been covered
         */
        public boolean addBookieAndCheckCovered(int bookieIndexHeardFrom);
    }

    public QuorumCoverageSet getCoverageSet();
    
    /**
     * Whether entry presents on given bookie index
     * 
     * @param entryId
     *            - entryId to check the presence on given bookie index
     * @param bookieIndex
     *            - bookie index on which it need to check the possible presence
     *            of the entry
     * @return true if it has entry otherwise false.
     */
    public boolean hasEntry(long entryId, int bookieIndex);
}