nblair.pipeline.AbstractParallelPipelineStep.java Source code

Introduction

Here is the source code for nblair.pipeline.AbstractParallelPipelineStep.java

Source

/**
 *    Copyright 2012, Board of Regents of the University of Wisconsin System
 *
 *    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 nblair.pipeline;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;

/**
 * Super class for {@link PipelineStep}s that provide a configurable number of workers.
 * {@link #accept(Object)} and {@link #blockUntilComplete()} are implemented to perform
 * concurrent execution of {@link PipelineStepCallable}s returned by subclass' {@link #constructCallableForWorkUnit(Object)} implementations
 * via an {@link ExecutorService}.
 * 
 * @see PipelineThreadPoolExecutor
 * @author Nicholas Blair
 */
public abstract class AbstractParallelPipelineStep<W> implements PipelineStep<W>, InitializingBean, DisposableBean {

    protected final Log log = LogFactory.getLog(this.getClass());
    private ThreadPoolExecutor executorService;
    private PipelineStep<W> nextStep;
    private int queueCapacity;

    /**
     * @return the nextStep
     */
    public PipelineStep<W> getNextStep() {
        return nextStep;
    }

    /**
     * @param nextStep the nextStep to set
     */
    public void setNextStep(PipelineStep<W> nextStep) {
        this.nextStep = nextStep;
    }

    /**
     * @return the queueCapacity
     */
    public int getQueueCapacity() {
        return queueCapacity;
    }

    /**
     * @param queueCapacity the queueCapacity to set
     */
    public void setQueueCapacity(int queueCapacity) {
        this.queueCapacity = queueCapacity;
    }

    /* (non-Javadoc)
     * @see org.springframework.beans.factory.DisposableBean#destroy()
     */
    @Override
    public final void destroy() throws Exception {
        this.executorService.shutdown();
    }

    /* (non-Javadoc)
     * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet()
     */
    @Override
    public final void afterPropertiesSet() throws Exception {
        this.executorService = new PipelineThreadPoolExecutor(getQueueCapacity(), getName());
    }

    /*
     * (non-Javadoc)
     * @see edu.wisc.wisccal.classsched.pipeline.SyncStep#accept(java.lang.Object)
     */
    @Override
    public final void accept(W workUnit) {
        if (shouldProcess(workUnit)) {
            PipelineStepCallable<W> task = constructCallableForWorkUnit(workUnit);
            this.executorService.submit(task);
        } else {
            if (log.isDebugEnabled()) {
                log.debug(
                        "shouldProcess on pipelineData for " + workUnit + " returned false for step " + getName());
            }
            // just because there was nothing to do in this step doesn't mean we shouldn't pass it to next step in the pipeline
            PipelineStep<W> nextStep = getNextStep();
            if (nextStep != null) {
                nextStep.accept(workUnit);
            }
        }
    }

    /*
     * (non-Javadoc)
     * @see edu.wisc.wisccal.classsched.pipeline.SyncStep#blockUntilComplete()
     */
    @Override
    public final void blockUntilComplete() {
        this.executorService.shutdown();
        try {
            // no "await indefinitely", 10 DAYS seemingly long enough
            this.executorService.awaitTermination(10, TimeUnit.DAYS);
        } catch (InterruptedException e) {
            throw new IllegalStateException("Interrupted in executorService#awaitTermination in step " + getName(),
                    e);
        }
        getNextStep().blockUntilComplete();
    }

    /**
     * Construct a {@link PipelineStepCallable} to perform work on the unit.
     * 
     * @param workUnit
     * @return a {@link PipelineStepCallable} implementation that performs work on the workUnit
     */
    public abstract PipelineStepCallable<W> constructCallableForWorkUnit(W workUnit);
}