co.cask.cdap.internal.pipeline.SynchronousPipeline.java Source code

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Here is the source code for co.cask.cdap.internal.pipeline.SynchronousPipeline.java

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/*
 * Copyright  2014 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.internal.pipeline;

import co.cask.cdap.pipeline.Context;
import co.cask.cdap.pipeline.Pipeline;
import co.cask.cdap.pipeline.Stage;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Concrete implementation of synchronous {@link Pipeline}.
 * <p>
 * Input from each {@link Stage} is passed to next {@link Stage}.
 * Before processing to next {@link Stage}, we wait for results
 * to be available.
 * </p>
 *
 * @param <T> Type of object produced by this pipeline.
 */
public final class SynchronousPipeline<T> extends AbstractPipeline<T> {

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

    /**
     * Executes a pipeline in synchronous mode.
     * <p>
     * Waits for the results of previous to be available to move to next
     * stage of processing.
     * </p>
     *
     * @param o argument to run the pipeline.
     */
    @SuppressWarnings("unchecked")
    @Override
    public ListenableFuture<T> execute(Object o) {
        Context ctx = new StageContext(o);
        try {
            for (Stage stage : getStages()) {
                stage.process(ctx);
                // Output of previous stage is input to next stage
                ctx = new StageContext(ctx.getDownStream());
            }
            return Futures.immediateFuture((T) ctx.getUpStream());
        } catch (Throwable th) {
            return Futures.immediateFailedFuture(th);
        } finally {
            Stage finalStage = getFinalStage();
            if (finalStage != null) {
                try {
                    finalStage.process(ctx);
                } catch (Throwable t) {
                    LOG.warn("Exception thrown when executing final stage {}", finalStage, t);
                }
            }
        }
    }
}