co.cask.cdap.template.etl.common.TransformExecutor.java Source code

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Here is the source code for co.cask.cdap.template.etl.common.TransformExecutor.java

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/*
 * Copyright  2015 Cask Data, Inc.
 *
 * Licensed 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 co.cask.cdap.template.etl.common;

import co.cask.cdap.template.etl.api.Destroyable;
import co.cask.cdap.template.etl.api.Transformation;
import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.List;

/**
 * Executes Transforms one iteration at a time, tracking how many records were input into and output from
 * each transform.
 *
 * @param <IN> the type of input object to the first transform
 * @param <OUT> the type of object output by the last transform
 */
public class TransformExecutor<IN, OUT> implements Destroyable {

    private static final Logger LOG = LoggerFactory.getLogger(TransformExecutor.class);

    private final List<Transformation> transforms;
    private final List<DefaultEmitter> emitters;

    public TransformExecutor(List<Transformation> transforms, List<StageMetrics> transformMetrics) {
        int numTransforms = transforms.size();
        Preconditions.checkArgument(numTransforms == transformMetrics.size());
        this.transforms = Lists.newArrayListWithCapacity(numTransforms);
        this.emitters = Lists.newArrayListWithCapacity(numTransforms);
        for (int i = 0; i < numTransforms; i++) {
            StageMetrics stageMetrics = transformMetrics.get(i);
            this.transforms.add(new TrackedTransform(transforms.get(i), stageMetrics));
            this.emitters.add(new DefaultEmitter(stageMetrics));
        }
    }

    public Iterable<OUT> runOneIteration(IN input) throws Exception {
        if (transforms.isEmpty()) {
            return Lists.newArrayList((OUT) input);
        }

        Transformation transform = transforms.get(0);
        DefaultEmitter currentEmitter = emitters.get(0);
        currentEmitter.reset();
        transform.transform(input, currentEmitter);

        DefaultEmitter previousEmitter = currentEmitter;

        for (int i = 1; i < transforms.size(); i++) {
            transform = transforms.get(i);
            currentEmitter = emitters.get(i);
            currentEmitter.reset();
            for (Object transformedVal : previousEmitter) {
                transform.transform(transformedVal, currentEmitter);
            }
            previousEmitter.reset();
            previousEmitter = currentEmitter;
        }

        return previousEmitter;
    }

    @Override
    public void destroy() {
        for (Transformation transform : transforms) {
            if (transform instanceof Destroyable) {
                Destroyables.destroyQuietly((Destroyable) transform);
            }
        }
    }
}