rate control in java

Question

I am looking for a good solution or probably an API to solve the following problem:

• My application does a task in a loop, for example it sends e-mails etc. I need to limit the average rate of messages to for example 100 messages per second or 1000 messages per last minute ...

No I am looking for an algorithm or an API which does exactly this task.

Answer 1

You can use a ScheduledExecutorService to schedule tasks for a given period of time.

For example, to schedule 100 tasks per second you can say:

ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(nThreads);
scheduler.scheduleAtFixedRate(mailSender, 0, 10, TimeUnit.MILLISECONDS);

Obviously, you need to track how many tasks have executed and turn off the scheduler after the job is done.

Answer 2

Token bucket algorithm is very easy to implement and use yet very powerful. You can control the throughput at runtime and queue some requests to handle peeks.

Answer 3

The simplest way I can think of is to delay when to send each emails depending on how many are waiting.

final ScheduledThreadPoolExecutor service = new ScheduledThreadPoolExecutor(1);
int ratePerSecond = ...

public static void execute(Runnable run) {
   int delay = 1000 * service.getQueue().size() / ratePerSecond;
   service.schedule(run, delay, TimeUnit.MILLISECONDS);
}

This will ensure that the tasks are performed only as close to together as the rate allows.

Answer 4

Guava has a RateLimiter class that does exactly that.