BlockingQueue and putAll

Question

Does anybody know why java's BlockingQueue does not have a putAll method? Is there a problem with such a method? Any good ways around this problem without having to completely re-implement BlockingQueue?

Answer 1

for (Item item : items) {
    queue.put(item);
}

3 lines, not sure thats totally re-implementing blocking queue.

I imagine it wants you to put 1 by 1 in case threads are waiting to read from it, they aren't waiting for you to finish reading them all.

Answer 2

I found the same issue with ArrayBlockingQueue. We wanted some additional methods that were missing:

• void putAll(Collection<? extends E> c) throws InterruptedException
• int drainAtLeastOneTo(@OutputParam Collection<? super E> c) throws InterruptedException
• int drainAtLeastOneTo(@OutputParam Collection<? super E> c, int maxElements) throws InterruptedException

Some people advocate to use BlockingQueue<List<E>>, but that requires malloc'ing lists. Sometimes you want to avoid it. Also, that assumes you want producer and consumer to use the same "chunk" sizes.

Regarding draining: Again, you may want to have a mismatch between chunk size of producer and consumer. So producer might insert single items, but consumer works on batches. drainTo() does not block, so drainAtLeastOneTo() was a solution.

In the end, we copied the default impl of ArrayBlockingQueue and added the methods directly. Again, a drawback is that you need to operate on a concrete type, instead of interface BlockingQueue.

You may also consider using the famed (infamous?) LMAX Disruptor, but the model is quite different from a standard BlockingQueue, as you do not control when items are consumed.