ThrottledInputStream.java

/**
 * 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 utils;

import java.io.IOException;
import java.io.InputStream;

/**
 * The ThrottleInputStream provides bandwidth throttling on a specified InputStream. It is implemented as a wrapper on top of another InputStream
 * instance. The throttling works by examining the number of bytes read from the underlying InputStream from the beginning, and sleep()ing for a time
 * interval if the byte-transfer is found exceed the specified tolerable maximum. (Thus, while the read-rate might exceed the maximum for a given
 * short interval, the average tends towards the specified maximum, overall.)
 */
public class ThrottledInputStream extends InputStream {

    private final InputStream rawStream;
    private final long maxBytesPerSec;
    private final long startTime = System.currentTimeMillis();

    private long bytesRead = 0;
    private long totalSleepTime = 0;

    private static final long SLEEP_DURATION_MS = 50;

    public ThrottledInputStream(InputStream rawStream) {
        this(rawStream, Long.MAX_VALUE);
    }

    public ThrottledInputStream(InputStream rawStream,
                                long maxBytesPerSec) {
        assert maxBytesPerSec > 0 : "Bandwidth " + maxBytesPerSec + " is invalid";
        this.rawStream = rawStream;
        this.maxBytesPerSec = maxBytesPerSec;
    }

    @Override
    public void close() throws IOException {
        rawStream.close();
    }

    /** @inheritDoc */
    @Override
    public int read() throws IOException {
        throttle();
        int data = rawStream.read();
        if (data != -1) {
            bytesRead++;
        }
        return data;
    }

    /** @inheritDoc */
    @Override
    public int read(byte[] b) throws IOException {
        throttle();
        int readLen = rawStream.read(b);
        if (readLen != -1) {
            bytesRead += readLen;
        }
        return readLen;
    }

    /** @inheritDoc */
    @Override
    public int read(byte[] b, int off, int len) throws IOException {
        throttle();
        int readLen = rawStream.read(b, off, len);
        if (readLen != -1) {
            bytesRead += readLen;
        }
        return readLen;
    }

    private void throttle() throws IOException {
        if (getBytesPerSec() > maxBytesPerSec) {
            try {
                Thread.sleep(SLEEP_DURATION_MS);
                totalSleepTime += SLEEP_DURATION_MS;
            } catch (InterruptedException e) {
                throw new IOException("Thread aborted", e);
            }
        }
    }

    /**
     * Getter for the number of bytes read from this stream, since creation.
     *
     * @return The number of bytes.
     */
    public long getTotalBytesRead() {
        return bytesRead;
    }

    /**
     * Getter for the read-rate from this stream, since creation. Calculated as bytesRead/elapsedTimeSinceStart.
     *
     * @return Read rate, in bytes/sec.
     */
    public long getBytesPerSec() {
        long elapsed = (System.currentTimeMillis() - startTime) / 1000;
        if (elapsed == 0) {
            return bytesRead;
        } else {
            return bytesRead / elapsed;
        }
    }

    /**
     * Getter the total time spent in sleep.
     *
     * @return Number of milliseconds spent in sleep.
     */
    public long getTotalSleepTime() {
        return totalSleepTime;
    }

    /** @inheritDoc */
    @Override
    public String toString() {
        return "ThrottledInputStream{"
               + "bytesRead="
               + bytesRead
               + ", maxBytesPerSec="
               + maxBytesPerSec
               + ", bytesPerSec="
               + getBytesPerSec()
               + ", totalSleepTime="
               + totalSleepTime
               + '}';
    }
}