Does httplib use I/O multiplexing (`select`, `poll`, `epoll`) and support thousands of concurrent connections?

[Mq-b]

Hello!

First of all, I want to say that I really like httplib—it's a very user-friendly library. I would like to know whether it utilizes I/O multiplexing techniques such as select, poll, or epoll. Additionally, does it support handling thousands of concurrent client connections efficiently?

Thank you!
Thank you!

cpp-httplib/README.md

Line 875 in a4b2c61

Use `select()` instead of `poll()`

[falbrechtskirchinger]

No, each connection is handled in a blocking manner on a dedicated thread (using poll()/select() on a single socket). As a result, you're limited by the size of the thread pool.

[Mq-b]

What if I don't have it set by default?

I mean I didn't use svr.new_task_queue.

[falbrechtskirchinger]

What if I don't have it set by default?

I mean I didn't use svr.new_task_queue.

From the link:

ThreadPool is used as a default task queue, and the default thread count is 8, or std::thread::hardware_concurrency(). You can change it with CPPHTTPLIB_THREAD_POOL_COUNT.

Looking at the source, it's actually std::thread::hardware_concurrency() - 1.

cpp-httplib/httplib.h

Lines 129 to 134 in a4b2c61

	#ifndef CPPHTTPLIB_THREAD_POOL_COUNT
	#define CPPHTTPLIB_THREAD_POOL_COUNT \
	((std::max)(8u, std::thread::hardware_concurrency() > 0 \
	? std::thread::hardware_concurrency() - 1 \
	: 0))
	#endif

[Mq-b]

I know, I mean, creating a new thread every time there's a new connection? Or is there an implementation of a thread pool inside httplib that doesn't create destruction threads all the time?

[falbrechtskirchinger]

(...) is there an implementation of a thread pool inside httplib that doesn't create destruction threads all the time?

Yes, threads are reused. That's the point of the task queue.

cpp-httplib/httplib.h

Lines 779 to 787 in a4b2c61

	class ThreadPool final : public TaskQueue {
	public:
	explicit ThreadPool(size_t n, size_t mqr = 0)
	: shutdown_(false), max_queued_requests_(mqr) {
	while (n) {
	threads_.emplace_back(worker(*this));
	n--;
	}
	}

[Mq-b]

Thanks, as long as threads aren't created and destroyed all the time, this library should be fine for me at the moment.