libs/corosio/src/corosio/src/detail/posix/resolver_service.hpp

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1		//
2		// Copyright (c) 2026 Steve Gerbino
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_DETAIL_POSIX_RESOLVER_SERVICE_HPP
11		#define BOOST_COROSIO_DETAIL_POSIX_RESOLVER_SERVICE_HPP
12
13		#include <boost/corosio/detail/platform.hpp>
14
15		#if BOOST_COROSIO_POSIX
16
17		#include <boost/corosio/detail/config.hpp>
18		#include <boost/corosio/resolver.hpp>
19		#include <boost/capy/ex/execution_context.hpp>
20
21		/*
22		POSIX Resolver Service
23		======================
24
25		POSIX getaddrinfo() is a blocking call that cannot be monitored with
26		epoll/kqueue/io_uring. We use a worker thread approach: each resolution
27		spawns a dedicated thread that runs the blocking call and posts completion
28		back to the scheduler.
29
30		This follows the timer_service pattern:
31		- posix_resolver_service is an abstract base class (no scheduler dependency)
32		- posix_resolver_service_impl is the concrete implementation
33		- get_resolver_service(ctx, sched) creates the service with scheduler ref
34
35		Thread-per-resolution Design
36		----------------------------
37		Simple, no thread pool complexity. DNS lookups are infrequent enough that
38		thread creation overhead is acceptable. Detached threads self-manage;
39		shared_ptr capture keeps impl alive until completion.
40
41		Cancellation
42		------------
43		getaddrinfo() cannot be interrupted mid-call. We use an atomic flag to
44		indicate cancellation was requested. The worker thread checks this flag
45		after getaddrinfo() returns and reports the appropriate error.
46		*/
47
48		namespace boost::corosio::detail {
49
50		struct scheduler;
51
52		//------------------------------------------------------------------------------
53
54		/** Abstract resolver service for POSIX backends.
55
56		This is the base class that defines the interface. The concrete
57		implementation (posix_resolver_service_impl) is created via
58		get_resolver_service() which passes the scheduler reference.
59		*/
60		class posix_resolver_service : public capy::execution_context::service
61		{
62		public:
63		/** Create a new resolver implementation. */
64		virtual resolver::resolver_impl& create_impl() = 0;
65
66		protected:
67	304	posix_resolver_service() = default;
68		};
69
70		//------------------------------------------------------------------------------
71
72		/** Get or create the resolver service for the given context.
73
74		This function is called by the concrete scheduler during initialization
75		to create the resolver service with a reference to itself.
76
77		@param ctx Reference to the owning execution_context.
78		@param sched Reference to the scheduler for posting completions.
79		@return Reference to the resolver service.
80		*/
81		posix_resolver_service&
82		get_resolver_service(capy::execution_context& ctx, scheduler& sched);
83
84		} // namespace boost::corosio::detail
85
86		#endif // BOOST_COROSIO_POSIX
87
88		#endif // BOOST_COROSIO_DETAIL_POSIX_RESOLVER_SERVICE_HPP
89