如何创建Java并发队列，从中我们可以在单个调用中阻塞多个元素？

Question

Background: I need to send many small-size messages to WebSocket clients in asynchronous way. Messages are usually sent in peak, so after some pause I need to send ~5000 messages fast. So the problem is:

• I don't want to start 5000 async's in single thread
• I don't want to loop "start async"-"wait for complete" 5000 times in serial
• I don't want to use 5000 threads, with single "start async"-"wait for complete" per thread

The best way would be to group ~20 asyncs per thread, so I need very specific queue :

• lot of means concurrent push/poll in queue
• small-sized asynchronous means I want to poll in bundles, like 1 to 20 messages per queue take() (so I can start 1...20 async I/O and wait for completness in single thread)
• immediately means that I dont want to wait until 20 messages will be polled, bundle-poll should be used only if queue has lot of messages. Single message should be polled and sent immediately.

So basically: I need structure like queue that has blocking take(1 to X) waiting elements in single blocking call . Pseudocode:

[each of ~50 processing threads]:
messages = queue.blockingTake( max 10 or at least 1 if less than 10 available );
for each message: message.startAsync()
for each message: message.waitToComplete()
repeat

Answer 1

I wouldn't implement a Queue from scratch if it's not really necessary. A few ideas if you're interested:

Queue> if you have only 1 thread doing the offers. If you have more, the collection has to be sync'd. Like, one offerer peek()-s into the queue, sees that the last collection has too many elements so it creates a new one and offers it.

or

A number of running threads where the runnables take elements one by one from the queue.

or

1 queue per sending thread, if you keep the queue references you can then add elements to each of them in a round robin fashion.

or

subclass a BlockingQueue of your choice and create a "Collection take(int i)" method with a rewritten version of the normal take().