com.datatorrent.lib.io.SimpleSinglePortInputOperator.java Source code

Introduction

Here is the source code for com.datatorrent.lib.io.SimpleSinglePortInputOperator.java

Source

/**
 * 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 com.datatorrent.lib.io;

import java.util.Iterator;
import java.util.concurrent.ArrayBlockingQueue;

import org.apache.commons.lang3.ClassUtils;

import com.datatorrent.api.Context.OperatorContext;
import com.datatorrent.api.DefaultOutputPort;
import com.datatorrent.api.InputOperator;
import com.datatorrent.api.Operator;
import com.datatorrent.common.util.BaseOperator;

/**
 * This an input operator which passes data from an asynchronous data source to a port processing thread.
 * <p>
 * This operator handles hand over from asynchronous input to port processing thread (tuples
 * must be emitted by container thread). If derived class implements
 * {@link Runnable} to perform synchronous IO, this class will manage the thread
 * according to the operator lifecycle.
 * </p>
 * @displayName Asynchronous Input Processing
 * @category Input
 *
 * @since 0.3.2
 */
@org.apache.hadoop.classification.InterfaceStability.Evolving
public abstract class SimpleSinglePortInputOperator<T> extends BaseOperator
        implements InputOperator, Operator.ActivationListener<OperatorContext> {
    private transient Thread ioThread;
    private transient boolean isActive = false;
    /**
     * The single output port of this input operator.
     * Collects asynchronously emitted tuples and flushes in container thread.
     */
    public final transient BufferingOutputPort<T> outputPort;

    public SimpleSinglePortInputOperator(int portCapacity) {
        outputPort = new BufferingOutputPort<T>(this, portCapacity);
    }

    public SimpleSinglePortInputOperator() {
        this(1024);
    }

    @Override
    public final void activate(OperatorContext ctx) {
        isActive = true;
        if (this instanceof Runnable) {
            ioThread = new Thread((Runnable) this, "io-" + ClassUtils.getShortClassName(this.getClass()));
            ioThread.start();
        }
    }

    @Override
    public final void deactivate() {
        isActive = false;
        if (ioThread != null) {
            // thread to exit sleep or blocking IO
            ioThread.interrupt();
        }
    }

    public final boolean isActive() {
        return isActive;
    }

    @Override
    public void emitTuples() {
        outputPort.flush(Integer.MAX_VALUE);
    }

    public static class BufferingOutputPort<T> extends DefaultOutputPort<T> {
        public final ArrayBlockingQueue<T> tuples;

        /**
         * @param operator
         */
        public BufferingOutputPort(Operator operator) {
            super();
            tuples = new ArrayBlockingQueue<T>(1024);
        }

        public BufferingOutputPort(Operator operator, int capacity) {
            super();
            tuples = new ArrayBlockingQueue<T>(capacity);
        }

        @Override
        public void emit(T tuple) {
            try {
                tuples.put(tuple);
            } catch (InterruptedException ex) {
                throw new RuntimeException(ex);
            }
        }

        public void flush(int count) {
            Iterator<T> iterator = tuples.iterator();
            while (count-- > 0 && iterator.hasNext()) {
                super.emit(iterator.next());
                iterator.remove();
            }
        }

    }

}