JDK provides a convenient
java.util.concurrent.Executors factory with useful methods to return various
java.util.concurrent.Executor implementation instance pre-configured with commonly used settings. However, there is no implementation or configuration available for an implementation that throttles task submission. Here I provide my take on a very simple solution for this requirement.
private void submitTasks(List tasksList) {
final ThreadPoolExecutor executor = new ThreadPoolExecutor(MIN_POOL_SIZE,
MAX_POOL_SIZE,
60L,
TimeUnit.SECONDS,
new LinkedBlockingQueue());
for (Runnable task : tasksList) {
while (executor.getQueue().size() > MAX_Q_SIZE) {
// Throttle for WAIT_FOR_SECONDS seconds if queue is full
try {
log.info("Waiting " + WAIT_FOR_SECONDS + " seconds as Queue size is: " + executor.getQueue().size());
Thread.sleep(WAIT_FOR_SECONDS * 1000);
} catch (InterruptedException e) {
// Ignore
}
}
executor.execute(task);
}
// inform the executor there are no more tasks
executor.shutdown();
}
Instead of using the factory to get a pre-configured executor, I create my own
ThreadPoolExecutor using a
LinkedBlockingQueue. This allows us access to the underlying queue for the throttling feature. Before submitting the task, I check if the current queue size is greater than a certain size and if so, then wait for a configured time repeatedly till the queue is smaller.
This implementation is very useful for the scenarios where you have lots of short running tasks that need to be processed by a fixed small number of threads.
