TLA Line data Source code
1 : //
2 : // Copyright (c) 2026 Vinnie Falco (vinnie.falco@gmail.com)
3 : //
4 : // Distributed under the Boost Software License, Version 1.0. (See accompanying
5 : // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
6 : //
7 : // Official repository: https://github.com/cppalliance/corosio
8 : //
9 :
10 : #ifndef BOOST_COROSIO_TCP_SERVER_HPP
11 : #define BOOST_COROSIO_TCP_SERVER_HPP
12 :
13 : #include <boost/corosio/detail/config.hpp>
14 : #include <boost/corosio/detail/except.hpp>
15 : #include <boost/corosio/tcp_acceptor.hpp>
16 : #include <boost/corosio/tcp_socket.hpp>
17 : #include <boost/corosio/io_context.hpp>
18 : #include <boost/corosio/endpoint.hpp>
19 : #include <boost/capy/task.hpp>
20 : #include <boost/capy/concept/execution_context.hpp>
21 : #include <boost/capy/concept/io_awaitable.hpp>
22 : #include <boost/capy/concept/executor.hpp>
23 : #include <boost/capy/ex/any_executor.hpp>
24 : #include <boost/capy/ex/frame_allocator.hpp>
25 : #include <boost/capy/ex/io_env.hpp>
26 : #include <boost/capy/ex/run_async.hpp>
27 :
28 : #include <coroutine>
29 : #include <memory>
30 : #include <ranges>
31 : #include <vector>
32 :
33 : namespace boost::corosio {
34 :
35 : #ifdef _MSC_VER
36 : #pragma warning(push)
37 : #pragma warning(disable : 4251) // class needs to have dll-interface
38 : #endif
39 :
40 : /** TCP server with pooled workers.
41 :
42 : This class manages a pool of reusable worker objects that handle
43 : incoming connections. When a connection arrives, an idle worker
44 : is dispatched to handle it. After the connection completes, the
45 : worker returns to the pool for reuse, avoiding allocation overhead
46 : per connection.
47 :
48 : Workers are set via @ref set_workers as a forward range of
49 : pointer-like objects (e.g., `unique_ptr<worker_base>`). The server
50 : takes ownership of the container via type erasure.
51 :
52 : @par Thread Safety
53 : Distinct objects: Safe.
54 : Shared objects: Unsafe.
55 :
56 : @par Lifecycle
57 : The server operates in three states:
58 :
59 : - **Stopped**: Initial state, or after @ref join completes.
60 : - **Running**: After @ref start, actively accepting connections.
61 : - **Stopping**: After @ref stop, draining active work.
62 :
63 : State transitions:
64 : @code
65 : [Stopped] --start()--> [Running] --stop()--> [Stopping] --join()--> [Stopped]
66 : @endcode
67 :
68 : @par Running the Server
69 : @code
70 : io_context ioc;
71 : tcp_server srv(ioc, ioc.get_executor());
72 : srv.set_workers(make_workers(ioc, 100));
73 : if (auto ec = srv.bind(endpoint{ipv4_address::any(), 8080}))
74 : return;
75 : srv.start();
76 : ioc.run(); // Blocks until all work completes
77 : @endcode
78 :
79 : @par Graceful Shutdown
80 : To shut down gracefully, call @ref stop then drain the io_context:
81 : @code
82 : // From a signal handler or timer callback:
83 : srv.stop();
84 :
85 : // ioc.run() returns after pending work drains.
86 : // Then from the thread that called ioc.run():
87 : srv.join(); // Wait for accept loops to finish
88 : @endcode
89 :
90 : @par Restart After Stop
91 : The server can be restarted after a complete shutdown cycle.
92 : You must drain the io_context and call @ref join before restarting:
93 : @code
94 : srv.start();
95 : ioc.run_for( 10s ); // Run for a while
96 : srv.stop(); // Signal shutdown
97 : ioc.run(); // REQUIRED: drain pending completions
98 : srv.join(); // REQUIRED: wait for accept loops
99 :
100 : // Now safe to restart
101 : srv.start();
102 : ioc.run();
103 : @endcode
104 :
105 : @par WARNING: What NOT to Do
106 : - Do NOT call @ref join from inside a worker coroutine (deadlock).
107 : - Do NOT call @ref join from a thread running `ioc.run()` (deadlock).
108 : - Do NOT call @ref start without completing @ref join after @ref stop.
109 : - Do NOT call `ioc.stop()` for graceful shutdown; use @ref stop instead.
110 :
111 : @par Example
112 : @code
113 : class my_worker : public tcp_server::worker_base
114 : {
115 : corosio::tcp_socket sock_;
116 : capy::any_executor ex_;
117 : public:
118 : my_worker(io_context& ctx)
119 : : sock_(ctx)
120 : , ex_(ctx.get_executor())
121 : {
122 : }
123 :
124 : corosio::tcp_socket& socket() override { return sock_; }
125 :
126 : void run(launcher launch) override
127 : {
128 : launch(ex_, [](corosio::tcp_socket* sock) -> capy::task<>
129 : {
130 : // handle connection using sock
131 : co_return;
132 : }(&sock_));
133 : }
134 : };
135 :
136 : auto make_workers(io_context& ctx, int n)
137 : {
138 : std::vector<std::unique_ptr<tcp_server::worker_base>> v;
139 : v.reserve(n);
140 : for(int i = 0; i < n; ++i)
141 : v.push_back(std::make_unique<my_worker>(ctx));
142 : return v;
143 : }
144 :
145 : io_context ioc;
146 : tcp_server srv(ioc, ioc.get_executor());
147 : srv.set_workers(make_workers(ioc, 100));
148 : @endcode
149 :
150 : @see worker_base, set_workers, launcher
151 : */
152 : class BOOST_COROSIO_DECL tcp_server
153 : {
154 : public:
155 : class worker_base; ///< Abstract base for connection handlers.
156 : class launcher; ///< Move-only handle to launch worker coroutines.
157 :
158 : private:
159 : struct waiter
160 : {
161 : waiter* next;
162 : std::coroutine_handle<> h;
163 : capy::continuation cont;
164 : worker_base* w;
165 : };
166 :
167 : struct impl;
168 :
169 : static impl* make_impl(capy::execution_context& ctx);
170 :
171 : impl* impl_;
172 : capy::any_executor ex_;
173 : waiter* waiters_ = nullptr;
174 : worker_base* idle_head_ = nullptr; // Forward list: available workers
175 : worker_base* active_head_ =
176 : nullptr; // Doubly linked: workers handling connections
177 : worker_base* active_tail_ = nullptr; // Tail for O(1) push_back
178 : std::size_t active_accepts_ = 0; // Number of active do_accept coroutines
179 : std::shared_ptr<void> storage_; // Owns the worker container (type-erased)
180 : bool running_ = false;
181 :
182 : // Idle list (forward/singly linked) - push front, pop front
183 HIT 162 : void idle_push(worker_base* w) noexcept
184 : {
185 162 : w->next_ = idle_head_;
186 162 : idle_head_ = w;
187 162 : }
188 :
189 36 : worker_base* idle_pop() noexcept
190 : {
191 36 : auto* w = idle_head_;
192 36 : if (w)
193 36 : idle_head_ = w->next_;
194 36 : return w;
195 : }
196 :
197 42 : bool idle_empty() const noexcept
198 : {
199 42 : return idle_head_ == nullptr;
200 : }
201 :
202 : // Active list (doubly linked) - push back, remove anywhere
203 18 : void active_push(worker_base* w) noexcept
204 : {
205 18 : w->next_ = nullptr;
206 18 : w->prev_ = active_tail_;
207 18 : if (active_tail_)
208 4 : active_tail_->next_ = w;
209 : else
210 14 : active_head_ = w;
211 18 : active_tail_ = w;
212 18 : }
213 :
214 42 : void active_remove(worker_base* w) noexcept
215 : {
216 : // Skip if not in active list (e.g., after failed accept)
217 42 : if (w != active_head_ && w->prev_ == nullptr)
218 24 : return;
219 18 : if (w->prev_)
220 4 : w->prev_->next_ = w->next_;
221 : else
222 14 : active_head_ = w->next_;
223 18 : if (w->next_)
224 2 : w->next_->prev_ = w->prev_;
225 : else
226 16 : active_tail_ = w->prev_;
227 18 : w->prev_ = nullptr; // Mark as not in active list
228 : }
229 :
230 : template<capy::Executor Ex>
231 : struct launch_wrapper
232 : {
233 : struct promise_type
234 : {
235 : Ex ex; // Executor stored directly in frame (outlives child tasks)
236 : capy::io_env env_;
237 :
238 : // For regular coroutines: first arg is executor, second is stop token
239 : template<class E, class S, class... Args>
240 : requires capy::Executor<std::decay_t<E>>
241 : promise_type(E e, S s, Args&&...)
242 : : ex(std::move(e))
243 : , env_{
244 : capy::executor_ref(ex), std::move(s),
245 : capy::get_current_frame_allocator()}
246 : {
247 : }
248 :
249 : // For lambda coroutines: first arg is closure, second is executor, third is stop token
250 : template<class Closure, class E, class S, class... Args>
251 : requires(!capy::Executor<std::decay_t<Closure>> &&
252 : capy::Executor<std::decay_t<E>>)
253 18 : promise_type(Closure&&, E e, S s, Args&&...)
254 18 : : ex(std::move(e))
255 18 : , env_{
256 18 : capy::executor_ref(ex), std::move(s),
257 18 : capy::get_current_frame_allocator()}
258 : {
259 18 : }
260 :
261 18 : launch_wrapper get_return_object() noexcept
262 : {
263 : return {
264 18 : std::coroutine_handle<promise_type>::from_promise(*this)};
265 : }
266 18 : std::suspend_always initial_suspend() noexcept
267 : {
268 18 : return {};
269 : }
270 18 : std::suspend_never final_suspend() noexcept
271 : {
272 18 : return {};
273 : }
274 18 : void return_void() noexcept {}
275 MIS 0 : void unhandled_exception()
276 : {
277 0 : std::terminate();
278 : }
279 :
280 : // Inject io_env for IoAwaitable
281 : template<capy::IoAwaitable Awaitable>
282 HIT 36 : auto await_transform(Awaitable&& a)
283 : {
284 : using AwaitableT = std::decay_t<Awaitable>;
285 : struct adapter
286 : {
287 : AwaitableT aw;
288 : capy::io_env const* env;
289 :
290 36 : bool await_ready()
291 : {
292 36 : return aw.await_ready();
293 : }
294 36 : decltype(auto) await_resume()
295 : {
296 36 : return aw.await_resume();
297 : }
298 :
299 36 : auto await_suspend(std::coroutine_handle<promise_type> h)
300 : {
301 36 : return aw.await_suspend(h, env);
302 : }
303 : };
304 54 : return adapter{std::forward<Awaitable>(a), &env_};
305 18 : }
306 : };
307 :
308 : std::coroutine_handle<promise_type> h;
309 :
310 18 : launch_wrapper(std::coroutine_handle<promise_type> handle) noexcept
311 18 : : h(handle)
312 : {
313 18 : }
314 :
315 18 : ~launch_wrapper()
316 : {
317 18 : if (h)
318 MIS 0 : h.destroy();
319 HIT 18 : }
320 :
321 : launch_wrapper(launch_wrapper&& o) noexcept
322 : : h(std::exchange(o.h, nullptr))
323 : {
324 : }
325 :
326 : launch_wrapper(launch_wrapper const&) = delete;
327 : launch_wrapper& operator=(launch_wrapper const&) = delete;
328 : launch_wrapper& operator=(launch_wrapper&&) = delete;
329 : };
330 :
331 : // Named functor to avoid incomplete lambda type in coroutine promise
332 : template<class Executor>
333 : struct launch_coro
334 : {
335 18 : launch_wrapper<Executor> operator()(
336 : Executor,
337 : std::stop_token,
338 : tcp_server* self,
339 : capy::task<void> t,
340 : worker_base* wp)
341 : {
342 : // Executor and stop token stored in promise via constructor
343 : co_await std::move(t);
344 : co_await self->push(*wp); // worker goes back to idle list
345 36 : }
346 : };
347 :
348 : class push_awaitable
349 : {
350 : tcp_server& self_;
351 : worker_base& w_;
352 : capy::continuation cont_;
353 :
354 : public:
355 38 : push_awaitable(tcp_server& self, worker_base& w) noexcept
356 38 : : self_(self)
357 38 : , w_(w)
358 : {
359 38 : }
360 :
361 38 : bool await_ready() const noexcept
362 : {
363 38 : return false;
364 : }
365 :
366 : std::coroutine_handle<>
367 38 : await_suspend(std::coroutine_handle<> h, capy::io_env const*) noexcept
368 : {
369 : // Symmetric transfer to server's executor
370 38 : cont_.h = h;
371 38 : return self_.ex_.dispatch(cont_);
372 : }
373 :
374 38 : void await_resume() noexcept
375 : {
376 : // Running on server executor - safe to modify lists
377 : // Remove from active (if present), then wake waiter or add to idle
378 38 : self_.active_remove(&w_);
379 38 : if (self_.waiters_)
380 : {
381 6 : auto* wait = self_.waiters_;
382 6 : self_.waiters_ = wait->next;
383 6 : wait->w = &w_;
384 6 : wait->cont.h = wait->h;
385 6 : self_.ex_.post(wait->cont);
386 : }
387 : else
388 : {
389 32 : self_.idle_push(&w_);
390 : }
391 38 : }
392 : };
393 :
394 : class pop_awaitable
395 : {
396 : tcp_server& self_;
397 : waiter wait_;
398 :
399 : public:
400 42 : pop_awaitable(tcp_server& self) noexcept : self_(self), wait_{} {}
401 :
402 42 : bool await_ready() const noexcept
403 : {
404 42 : return !self_.idle_empty();
405 : }
406 :
407 : bool
408 6 : await_suspend(std::coroutine_handle<> h, capy::io_env const*) noexcept
409 : {
410 : // Running on server executor (do_accept runs there)
411 6 : wait_.h = h;
412 6 : wait_.w = nullptr;
413 6 : wait_.next = self_.waiters_;
414 6 : self_.waiters_ = &wait_;
415 6 : return true;
416 : }
417 :
418 42 : worker_base& await_resume() noexcept
419 : {
420 : // Running on server executor
421 42 : if (wait_.w)
422 6 : return *wait_.w; // Woken by push_awaitable
423 36 : return *self_.idle_pop();
424 : }
425 : };
426 :
427 38 : push_awaitable push(worker_base& w)
428 : {
429 38 : return push_awaitable{*this, w};
430 : }
431 :
432 : // Synchronous version for destructor/guard paths
433 : // Must be called from server executor context
434 4 : void push_sync(worker_base& w) noexcept
435 : {
436 4 : active_remove(&w);
437 4 : if (waiters_)
438 : {
439 MIS 0 : auto* wait = waiters_;
440 0 : waiters_ = wait->next;
441 0 : wait->w = &w;
442 0 : wait->cont.h = wait->h;
443 0 : ex_.post(wait->cont);
444 : }
445 : else
446 : {
447 HIT 4 : idle_push(&w);
448 : }
449 4 : }
450 :
451 42 : pop_awaitable pop()
452 : {
453 42 : return pop_awaitable{*this};
454 : }
455 :
456 : capy::task<void> do_accept(tcp_acceptor& acc);
457 :
458 : public:
459 : /** Abstract base class for connection handlers.
460 :
461 : Derive from this class to implement custom connection handling.
462 : Each worker owns a socket and is reused across multiple
463 : connections to avoid per-connection allocation.
464 :
465 : @see tcp_server, launcher
466 : */
467 : class BOOST_COROSIO_DECL worker_base
468 : {
469 : // Ordered largest to smallest for optimal packing
470 : std::stop_source stop_; // ~16 bytes
471 : worker_base* next_ = nullptr; // 8 bytes - used by idle and active lists
472 : worker_base* prev_ = nullptr; // 8 bytes - used only by active list
473 :
474 : friend class tcp_server;
475 :
476 : public:
477 : /// Construct a worker.
478 : worker_base();
479 :
480 : /// Destroy the worker.
481 : virtual ~worker_base();
482 :
483 : /** Handle an accepted connection.
484 :
485 : Called when this worker is dispatched to handle a new
486 : connection. The implementation must invoke the launcher
487 : exactly once to start the handling coroutine.
488 :
489 : @param launch Handle to launch the connection coroutine.
490 : */
491 : virtual void run(launcher launch) = 0;
492 :
493 : /// Return the socket used for connections.
494 : virtual corosio::tcp_socket& socket() = 0;
495 : };
496 :
497 : /** Move-only handle to launch a worker coroutine.
498 :
499 : Passed to @ref worker_base::run to start the connection-handling
500 : coroutine. The launcher ensures the worker returns to the idle
501 : pool when the coroutine completes or if launching fails.
502 :
503 : The launcher must be invoked exactly once via `operator()`.
504 : If destroyed without invoking, the worker is returned to the
505 : idle pool automatically.
506 :
507 : @see worker_base::run
508 : */
509 : class BOOST_COROSIO_DECL launcher
510 : {
511 : tcp_server* srv_;
512 : worker_base* w_;
513 :
514 : friend class tcp_server;
515 :
516 22 : launcher(tcp_server& srv, worker_base& w) noexcept : srv_(&srv), w_(&w)
517 : {
518 22 : }
519 :
520 : public:
521 : /// Return the worker to the pool if not launched.
522 22 : ~launcher()
523 : {
524 22 : if (w_)
525 4 : srv_->push_sync(*w_);
526 22 : }
527 :
528 : launcher(launcher&& o) noexcept
529 : : srv_(o.srv_)
530 : , w_(std::exchange(o.w_, nullptr))
531 : {
532 : }
533 : launcher(launcher const&) = delete;
534 : launcher& operator=(launcher const&) = delete;
535 : launcher& operator=(launcher&&) = delete;
536 :
537 : /** Launch the connection-handling coroutine.
538 :
539 : Starts the given coroutine on the specified executor. When
540 : the coroutine completes, the worker is automatically returned
541 : to the idle pool.
542 :
543 : @param ex The executor to run the coroutine on.
544 : @param task The coroutine to execute.
545 :
546 : @throws std::logic_error If this launcher was already invoked.
547 : */
548 : template<class Executor>
549 20 : void operator()(Executor const& ex, capy::task<void> task)
550 : {
551 20 : if (!w_)
552 2 : detail::throw_logic_error(); // launcher already invoked
553 :
554 18 : auto* w = std::exchange(w_, nullptr);
555 :
556 : // Worker is being dispatched - add to active list
557 18 : srv_->active_push(w);
558 :
559 : // Return worker to pool if coroutine setup throws
560 : struct guard_t
561 : {
562 : tcp_server* srv;
563 : worker_base* w;
564 18 : ~guard_t()
565 : {
566 18 : if (w)
567 MIS 0 : srv->push_sync(*w);
568 HIT 18 : }
569 18 : } guard{srv_, w};
570 :
571 : // Reset worker's stop source for this connection
572 18 : w->stop_ = {};
573 18 : auto st = w->stop_.get_token();
574 :
575 18 : auto wrapper =
576 18 : launch_coro<Executor>{}(ex, st, srv_, std::move(task), w);
577 :
578 : // Executor and stop token stored in promise via constructor
579 18 : ex.post(std::exchange(wrapper.h, nullptr)); // Release before post
580 18 : guard.w = nullptr; // Success - dismiss guard
581 18 : }
582 : };
583 :
584 : /** Construct a TCP server.
585 :
586 : @tparam Ctx Execution context type satisfying ExecutionContext.
587 : @tparam Ex Executor type satisfying Executor.
588 :
589 : @param ctx The execution context for socket operations.
590 : @param ex The executor for dispatching coroutines.
591 :
592 : @par Example
593 : @code
594 : tcp_server srv(ctx, ctx.get_executor());
595 : srv.set_workers(make_workers(ctx, 100));
596 : if (auto ec = srv.bind(endpoint{...}))
597 : return;
598 : srv.start();
599 : @endcode
600 : */
601 : template<capy::ExecutionContext Ctx, capy::Executor Ex>
602 36 : tcp_server(Ctx& ctx, Ex ex) : impl_(make_impl(ctx))
603 36 : , ex_(std::move(ex))
604 : {
605 36 : }
606 :
607 : public:
608 : /// Destroy the server, stopping all accept loops.
609 : ~tcp_server();
610 :
611 : tcp_server(tcp_server const&) = delete;
612 : tcp_server& operator=(tcp_server const&) = delete;
613 :
614 : /** Move construct from another server.
615 :
616 : @param o The source server. After the move, @p o is
617 : in a valid but unspecified state.
618 : */
619 : tcp_server(tcp_server&& o) noexcept;
620 :
621 : /** Move assign from another server.
622 :
623 : @param o The source server. After the move, @p o is
624 : in a valid but unspecified state.
625 :
626 : @return `*this`.
627 : */
628 : tcp_server& operator=(tcp_server&& o) noexcept;
629 :
630 : /** Bind to a local endpoint.
631 :
632 : Creates an acceptor listening on the specified endpoint.
633 : Multiple endpoints can be bound by calling this method
634 : multiple times before @ref start.
635 :
636 : @param ep The local endpoint to bind to.
637 :
638 : @return The error code if binding fails.
639 : */
640 : [[nodiscard]] std::error_code bind(endpoint ep);
641 :
642 : /** Set the worker pool.
643 :
644 : Replaces any existing workers with the given range. Any
645 : previous workers are released and the idle/active lists
646 : are cleared before populating with new workers.
647 :
648 : @tparam Range Forward range of pointer-like objects to worker_base.
649 :
650 : @param workers Range of workers to manage. Each element must
651 : support `std::to_address()` yielding `worker_base*`.
652 :
653 : @par Example
654 : @code
655 : std::vector<std::unique_ptr<my_worker>> workers;
656 : for(int i = 0; i < 100; ++i)
657 : workers.push_back(std::make_unique<my_worker>(ctx));
658 : srv.set_workers(std::move(workers));
659 : @endcode
660 : */
661 : template<std::ranges::forward_range Range>
662 : requires std::convertible_to<
663 : decltype(std::to_address(
664 : std::declval<std::ranges::range_value_t<Range>&>())),
665 : worker_base*>
666 36 : void set_workers(Range&& workers)
667 : {
668 : // Clear existing state
669 36 : storage_.reset();
670 36 : idle_head_ = nullptr;
671 36 : active_head_ = nullptr;
672 36 : active_tail_ = nullptr;
673 :
674 : // Take ownership and populate idle list
675 : using StorageType = std::decay_t<Range>;
676 36 : auto* p = new StorageType(std::forward<Range>(workers));
677 36 : storage_ = std::shared_ptr<void>(
678 36 : p, [](void* ptr) { delete static_cast<StorageType*>(ptr); });
679 162 : for (auto&& elem : *static_cast<StorageType*>(p))
680 126 : idle_push(std::to_address(elem));
681 36 : }
682 :
683 : /** Start accepting connections.
684 :
685 : Launches accept loops for all bound endpoints. Incoming
686 : connections are dispatched to idle workers from the pool.
687 :
688 : Calling `start()` on an already-running server has no effect.
689 :
690 : @par Preconditions
691 : - At least one endpoint bound via @ref bind.
692 : - Workers provided via @ref set_workers.
693 : - If restarting, @ref join must have completed first.
694 :
695 : @par Effects
696 : Creates one accept coroutine per bound endpoint. Each coroutine
697 : runs on the server's executor, waiting for connections and
698 : dispatching them to idle workers.
699 :
700 : @par Restart Sequence
701 : To restart after stopping, complete the full shutdown cycle:
702 : @code
703 : srv.start();
704 : ioc.run_for( 1s );
705 : srv.stop(); // 1. Signal shutdown
706 : ioc.run(); // 2. Drain remaining completions
707 : srv.join(); // 3. Wait for accept loops
708 :
709 : // Now safe to restart
710 : srv.start();
711 : ioc.run();
712 : @endcode
713 :
714 : @par Thread Safety
715 : Not thread safe.
716 :
717 : @throws std::logic_error If a previous session has not been
718 : joined (accept loops still active).
719 : */
720 : void start();
721 :
722 : /** Return the local endpoint for the i-th bound port.
723 :
724 : @param index Zero-based index into the list of bound ports.
725 :
726 : @return The local endpoint, or a default-constructed endpoint
727 : if @p index is out of range or the acceptor is not open.
728 : */
729 : endpoint local_endpoint(std::size_t index = 0) const noexcept;
730 :
731 : /** Stop accepting connections.
732 :
733 : Requests the accept loops' stop token and requests cancellation
734 : of active workers via their stop tokens. The acceptors are not
735 : closed; a suspended accept completes once more before its loop
736 : observes the stop token and ends.
737 :
738 : This function returns immediately; it does not wait for workers
739 : to finish. Pending I/O operations complete asynchronously.
740 :
741 : Calling `stop()` on a non-running server has no effect.
742 :
743 : @par Effects
744 : - Requests stop on the accept loops' stop token. The acceptors
745 : are not closed; a pending accept completes once more before
746 : the accept loop ends.
747 : - Requests stop on each active worker's stop token.
748 : - Workers observing their stop token should exit promptly.
749 :
750 : @par Postconditions
751 : No new connections will be accepted. Active workers continue
752 : until they observe their stop token or complete naturally.
753 :
754 : @par What Happens Next
755 : After calling `stop()`:
756 : 1. Let `ioc.run()` return (drains pending completions).
757 : 2. Call @ref join to wait for accept loops to finish.
758 : 3. Only then is it safe to restart or destroy the server.
759 :
760 : @par Thread Safety
761 : Not thread safe.
762 :
763 : @see join, start
764 : */
765 : void stop();
766 :
767 : /** Block until all accept loops complete.
768 :
769 : Blocks the calling thread until all accept coroutines launched
770 : by @ref start have finished executing. This synchronizes the
771 : shutdown sequence, ensuring the server is fully stopped before
772 : restarting or destroying it.
773 :
774 : @par Preconditions
775 : @ref stop has been called and `ioc.run()` has returned.
776 :
777 : @par Postconditions
778 : All accept loops have completed. The server is in the stopped
779 : state and may be restarted via @ref start.
780 :
781 : @par Example (Correct Usage)
782 : @code
783 : // main thread
784 : srv.start();
785 : ioc.run(); // Blocks until work completes
786 : srv.join(); // Safe: called after ioc.run() returns
787 : @endcode
788 :
789 : @par WARNING: Deadlock Scenarios
790 : Calling `join()` from the wrong context causes deadlock:
791 :
792 : @code
793 : // WRONG: calling join() from inside a worker coroutine
794 : void run( launcher launch ) override
795 : {
796 : launch( ex, [this]() -> capy::task<>
797 : {
798 : srv_.join(); // DEADLOCK: blocks the executor
799 : co_return;
800 : }());
801 : }
802 :
803 : // WRONG: calling join() while ioc.run() is still active
804 : std::thread t( [&]{ ioc.run(); } );
805 : srv.stop();
806 : srv.join(); // DEADLOCK: ioc.run() still running in thread t
807 : @endcode
808 :
809 : @par Thread Safety
810 : May be called from any thread, but will deadlock if called
811 : from within the io_context event loop or from a worker coroutine.
812 :
813 : @see stop, start
814 : */
815 : void join();
816 :
817 : private:
818 : capy::task<> do_stop();
819 : };
820 :
821 : #ifdef _MSC_VER
822 : #pragma warning(pop)
823 : #endif
824 :
825 : } // namespace boost::corosio
826 :
827 : #endif
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