src/main/java/org/apache/giraph/graph/BasicVertexResolver.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.giraph.graph;

import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.WritableComparable;

/**
 * Handles all the situations that can arise upon creation/removal of
 * vertices and edges.
 */
@SuppressWarnings("rawtypes")
public interface BasicVertexResolver<
        I extends WritableComparable,
        V extends Writable,
        E extends Writable,
        M extends Writable> {
    /**
     * A vertex may have been removed, created zero or more times and had
     * zero or more messages sent to it.  This method will handle all situations
     * excluding the normal case (a vertex already exists and has zero or more
     * messages sent it to).
     *
     * @param vertexId Vertex id (can be used for {@link BasicVertex}'s
     *        initialize())
     * @param vertex Original vertex or null if none
     * @param vertexChanges Changes that happened to this vertex or null if none
     * @param messages messages received in the last superstep or null if none
     * @return Vertex to be returned, if null, and a vertex currently exists
     *         it will be removed
     */
    BasicVertex<I, V, E, M> resolve(I vertexId,
                                    BasicVertex<I, V, E, M> vertex,
                                    VertexChanges<I, V, E, M> vertexChanges,
                                    Iterable<M> messages);

    /**
     * Create a default vertex that can be used to return from resolve().
     *
     * @return Newly instantiated vertex.
     */
    BasicVertex<I, V, E, M> instantiateVertex();
}