org.apache.beam.runners.spark.aggregators.SparkAggregators.java Source code

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Here is the source code for org.apache.beam.runners.spark.aggregators.SparkAggregators.java

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/*
 * 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.beam.runners.spark.aggregators;

import com.google.common.collect.ImmutableList;
import java.util.Collection;
import java.util.Map;
import org.apache.beam.runners.core.AggregatorFactory;
import org.apache.beam.runners.core.ExecutionContext;
import org.apache.beam.runners.spark.translation.SparkRuntimeContext;
import org.apache.beam.sdk.AggregatorValues;
import org.apache.beam.sdk.transforms.Aggregator;
import org.apache.beam.sdk.transforms.Combine;
import org.apache.spark.Accumulator;

/**
 * A utility class for handling Beam {@link Aggregator}s.
 */
public class SparkAggregators {

    private static <T> AggregatorValues<T> valueOf(final Accumulator<NamedAggregators> accum,
            final Aggregator<?, T> aggregator) {
        @SuppressWarnings("unchecked")
        Class<T> valueType = (Class<T>) aggregator.getCombineFn().getOutputType().getRawType();
        final T value = valueOf(accum, aggregator.getName(), valueType);

        return new AggregatorValues<T>() {

            @Override
            public Collection<T> getValues() {
                return ImmutableList.of(value);
            }

            @Override
            public Map<String, T> getValuesAtSteps() {
                throw new UnsupportedOperationException("getValuesAtSteps is not supported.");
            }
        };
    }

    private static <T> T valueOf(final Accumulator<NamedAggregators> accum, final String aggregatorName,
            final Class<T> typeClass) {
        return accum.value().getValue(aggregatorName, typeClass);
    }

    /**
     * Retrieves the value of an aggregator from a SparkContext instance.
     *
     * @param aggregator The aggregator whose value to retrieve
     * @param <T> The type of the aggregator's output
     * @return The value of the aggregator
     */
    public static <T> AggregatorValues<T> valueOf(final Aggregator<?, T> aggregator) {
        return valueOf(AggregatorsAccumulator.getInstance(), aggregator);
    }

    /**
     * Retrieves the value of an aggregator from a SparkContext instance.
     *
     * @param name Name of the aggregator to retrieve the value of.
     * @param typeClass      Type class of value to be retrieved.
     * @param <T>            Type of object to be returned.
     * @return The value of the aggregator.
     */
    public static <T> T valueOf(final String name, final Class<T> typeClass) {
        return valueOf(AggregatorsAccumulator.getInstance(), name, typeClass);
    }

    /**
     * An implementation of {@link AggregatorFactory} for the SparkRunner.
     */
    public static class Factory implements AggregatorFactory {

        private final SparkRuntimeContext runtimeContext;
        private final Accumulator<NamedAggregators> accumulator;

        public Factory(SparkRuntimeContext runtimeContext, Accumulator<NamedAggregators> accumulator) {
            this.runtimeContext = runtimeContext;
            this.accumulator = accumulator;
        }

        @Override
        public <InputT, AccumT, OutputT> Aggregator<InputT, OutputT> createAggregatorForDoFn(Class<?> fnClass,
                ExecutionContext.StepContext stepContext, String aggregatorName,
                Combine.CombineFn<InputT, AccumT, OutputT> combine) {

            return runtimeContext.createAggregator(accumulator, aggregatorName, combine);
        }
    }

}