Question

I’d like to programmatically limit an upload or download operation in Java. I would assume that all I’d need to do was do check how fast the upload is going and insert Thread.sleep() accordingly like so:

while (file.hasMoreLines()) {
    String line = file.readLine();
    for (int i = 0; i < line.length(); i+=128) {
        outputStream.writeBytes(line.substr(i, i+128).getBytes());
        if (isHittingLimit())
            Thread.sleep(500);
    }
}

Will the above code work? If not, is there a better way to do this? Is there a tutorial which describes the theory?

Answer 1

Token Bucket Algorithm is a way to limit an upload or a download’s bandwidth.
You should read this article : it explains the use of this algorithm.

Using Guava RateLimiter :

// rate = 512 permits per second or 512 bytes per second in this case
final RateLimiter rateLimiter = RateLimiter.create(512.0); 

while (file.hasMoreLines()) {
    String line = file.readLine();
    for (int i = 0; i < line.length(); i+=128) {
        byte[] bytes = line.substr(i, i+128).getBytes();
        rateLimiter.acquire(bytes.length);
        outputStream.writeBytes(bytes);
    }
}

As explained in Guava docs:
It is important to note that the number of permits requested never affects the throttling of the request itself (an invocation to acquire(1) and an invocation to acquire(1000) will result in exactly the same throttling, if any), but it affects the throttling of the next request. I.e., if an expensive task arrives at an idle RateLimiter, it will be granted immediately, but it is the next request that will experience extra throttling, thus paying for the cost of the expensive task.