src/main/java/org/apache/giraph/graph/WorkerContext.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.mapreduce.Mapper;

/**
 * WorkerContext allows for the execution of user code
 * on a per-worker basis. There's one WorkerContext per worker.
 */
@SuppressWarnings("rawtypes")
public abstract class WorkerContext implements AggregatorUsage {
    /** Global graph state */
	private GraphState graphState;

	public void setGraphState(GraphState graphState) {
		this.graphState = graphState;
	}

    /**
     * Initialize the WorkerContext.
     * This method is executed once on each Worker before the first
     * superstep starts.
     *
     * @throws IllegalAccessException
     * @throws InstantiationException
     */
	public abstract void preApplication() throws InstantiationException,
		IllegalAccessException;

    /**
     * Finalize the WorkerContext.
     * This method is executed once on each Worker after the last
     * superstep ends.
     */
    public abstract void postApplication();

    /**
     * Execute user code.
     * This method is executed once on each Worker before each
     * superstep starts.
     */
    public abstract void preSuperstep();

    /**
     * Execute user code.
     * This method is executed once on each Worker after each
     * superstep ends.
     */
    public abstract void postSuperstep();

    /**
     * Retrieves the current superstep.
     *
     * @return Current superstep
     */
    public long getSuperstep() {
        return graphState.getSuperstep();
    }

    /**
     * Get the total (all workers) number of vertices that
     * existed in the previous superstep.
     *
     * @return Total number of vertices (-1 if first superstep)
     */
    public long getNumVertices() {
    	return graphState.getNumVertices();
    }

    /**
     * Get the total (all workers) number of edges that
     * existed in the previous superstep.
     *
     * @return Total number of edges (-1 if first superstep)
     */
    public long getNumEdges() {
    	return graphState.getNumEdges();
    }

    /**
     * Get the mapper context
     *
     * @return Mapper context
     */
    public Mapper.Context getContext() {
        return graphState.getContext();
    }

    @Override
    public final <A extends Writable> Aggregator<A> registerAggregator(
            String name,
            Class<? extends Aggregator<A>> aggregatorClass)
            throws InstantiationException, IllegalAccessException {
        return graphState.getGraphMapper().getAggregatorUsage().
            registerAggregator(name, aggregatorClass);
    }

    @Override
    public final Aggregator<? extends Writable> getAggregator(String name) {
        return graphState.getGraphMapper().getAggregatorUsage().
            getAggregator(name);
    }

    @Override
    public final boolean useAggregator(String name) {
        return graphState.getGraphMapper().getAggregatorUsage().
            useAggregator(name);
    }
}