HTML Diff fork/process_per

src/examples/cpp03/fork/process_per_connection.cpp		src/examples/cpp11/fork/process_per_connection.cpp
⋮		⋮
1	//	1	//
2	//·process_per_connection.cpp	2	//·process_per_connection.cpp
3	//·~~~~~~~~~~~~~~~~~~~~~~~~~~	3	//·~~~~~~~~~~~~~~~~~~~~~~~~~~
4	//	4	//
5	//·Copyright·(c)·2003-2020·Christopher·M.·Kohlhoff·(chris·at·kohlhoff·dot·com)	5	//·Copyright·(c)·2003-2020·Christopher·M.·Kohlhoff·(chris·at·kohlhoff·dot·com)
6	//	6	//
7	//·Distributed·under·the·Boost·Software·License,·Version·1.0.·(See·accompanying	7	//·Distributed·under·the·Boost·Software·License,·Version·1.0.·(See·accompanying
8	//·file·LICENSE_1_0.txt·or·copy·at·http://www.boost.org/LICENSE_1_0.txt)	8	//·file·LICENSE_1_0.txt·or·copy·at·http://www.boost.org/LICENSE_1_0.txt)
9	//	9	//
10		10
11	#include·<asio/io_context.hpp>	11	#include·<asio/io_context.hpp>
12	#include·<asio/ip/tcp.hpp>	12	#include·<asio/ip/tcp.hpp>
13	#include·<asio/signal_set.hpp>	13	#include·<asio/signal_set.hpp>
14	#include·<asio/write.hpp>	14	#include·<asio/write.hpp>
15	#include·<boost/array.hpp>
16	#include·<boost/bind/bind.hpp>
17	#include·<cstdlib>	15	#include·<cstdlib>
18	#include·<iostream>	16	#include·<iostream>
19	#include·<sys/types.h>	17	#include·<sys/types.h>
20	#include·<sys/wait.h>	18	#include·<sys/wait.h>
21	#include·<unistd.h>	19	#include·<unistd.h>
22		20
23	using·asio::ip::tcp;	21	using·asio::ip::tcp;
24		22
25	class·server	23	class·server
26	{	24	{
27	public:	25	public:
28	··server(asio::io_context&·io_context,·unsigned·short·port)	26	··server(asio::io_context&·io_context,·unsigned·short·port)
29	····:·io_context_(io_context),	27	····:·io_context_(io_context),
30	······signal_(io_context,·SIGCHLD),	28	······signal_(io_context,·SIGCHLD),
31	······acceptor_(io_context,·tcp::endpoint(tcp::v4(),·port)),	29	······acceptor_(io_context,·{tcp::v4(),·port}),
32	······socket_(io_context)	30	······socket_(io_context)
33	··{	31	··{
34	····start_signal_wait();	32	····wait_for_signal();
35	····start_accept();	33	····accept();
36	··}	34	··}
37		35
38	private:	36	private:
39	··void·start_signal_wait()	37	··void·wait_for_signal()
40	··{	38	··{
41	····signal_.async_wait(boost::bind(&server::handle_signal_wait,·this));	39	····signal_.async_wait(
		40	········[this](std::error_code·/ec/,·int·/signo/)
		41	········{
		42	··········//·Only·the·parent·process·should·check·for·this·signal.·We·can
		43	··········//·determine·whether·we·are·in·the·parent·by·checking·if·the·acceptor
		44	··········//·is·still·open.
		45	··········if·(acceptor_.is_open())
		46	··········{
		47	············//·Reap·completed·child·processes·so·that·we·don't·end·up·with
		48	············//·zombies.
		49	············int·status·=·0;
		50	············while·(waitpid(-1,·&status,·WNOHANG)·>·0)·{}
		51
		52	············wait_for_signal();
		53	··········}
		54	········});
		55	··}
		56
		57	··void·accept()
		58	··{
		59	····acceptor_.async_accept(
		60	········[this](std::error_code·ec,·tcp::socket·new_socket)
		61	········{
		62	··········if·(!ec)
		63	··········{
		64	············//·Take·ownership·of·the·newly·accepted·socket.
		65	············socket_·=·std::move(new_socket);
		66
		67	············//·Inform·the·io_context·that·we·are·about·to·fork.·The·io_context
		68	············//·cleans·up·any·internal·resources,·such·as·threads,·that·may
		69	············//·interfere·with·forking.
		70	············io_context_.notify_fork(asio::io_context::fork_prepare);
		71
		72	············if·(fork()·==·0)
		73	············{
		74	··············//·Inform·the·io_context·that·the·fork·is·finished·and·that·this
		75	··············//·is·the·child·process.·The·io_context·uses·this·opportunity·to
		76	··············//·create·any·internal·file·descriptors·that·must·be·private·to
		77	··············//·the·new·process.
		78	··············io_context_.notify_fork(asio::io_context::fork_child);
		79
		80	··············//·The·child·won't·be·accepting·new·connections,·so·we·can·close
		81	··············//·the·acceptor.·It·remains·open·in·the·parent.
		82	··············acceptor_.close();
		83
		84	··············//·The·child·process·is·not·interested·in·processing·the·SIGCHLD
		85	··············//·signal.
		86	··············signal_.cancel();
		87
		88	··············read();
		89	············}
		90	············else
		91	············{
		92
		93	··············//·Inform·the·io_context·that·the·fork·is·finished·(or·failed)
		94	··············//·and·that·this·is·the·parent·process.·The·io_context·uses·this
		95	··············//·opportunity·to·recreate·any·internal·resources·that·were
		96	··············//·cleaned·up·during·preparation·for·the·fork.
		97	··············io_context_.notify_fork(asio::io_context::fork_parent);
		98
		99	··············//·The·parent·process·can·now·close·the·newly·accepted·socket.·It
		100	··············//·remains·open·in·the·child.
		101	··············socket_.close();
		102
		103	··············accept();
		104	············}
		105	··········}
		106	··········else
		107	··········{
		108	············std::cerr·<<·"Accept·error:·"·<<·ec.message()·<<·std::endl;
		109	············accept();
		110	··········}
		111	········});
42	··}	112	··}
43		113
44	··void·handle_signal_wait()	114	··void·read()
45	··{
46	····//·Only·the·parent·process·should·check·for·this·signal.·We·can·determine
47	····//·whether·we·are·in·the·parent·by·checking·if·the·acceptor·is·still·open.
48	····if·(acceptor_.is_open())
49	····{
50	······//·Reap·completed·child·processes·so·that·we·don't·end·up·with·zombies.
51	······int·status·=·0;
52	······while·(waitpid(-1,·&status,·WNOHANG)·>·0)·{}
53
54	······start_signal_wait();
55	····}
56	··}
57
58	··void·start_accept()
59	··{
60	····acceptor_.async_accept(socket_,
61	········boost::bind(&server::handle_accept,·this,·boost::placeholders::_1));
62	··}
63
64	··void·handle_accept(const·asio::error_code&·ec)
65	··{
66	····if·(!ec)
67	····{
68	······//·Inform·the·io_context·that·we·are·about·to·fork.·The·io_context·cleans
69	······//·up·any·internal·resources,·such·as·threads,·that·may·interfere·with
70	······//·forking.
71	······io_context_.notify_fork(asio::io_context::fork_prepare);
72
73	······if·(fork()·==·0)
74	······{
75	········//·Inform·the·io_context·that·the·fork·is·finished·and·that·this·is·the
76	········//·child·process.·The·io_context·uses·this·opportunity·to·create·any
77	········//·internal·file·descriptors·that·must·be·private·to·the·new·process.
78	········io_context_.notify_fork(asio::io_context::fork_child);
79
80	········//·The·child·won't·be·accepting·new·connections,·so·we·can·close·the
81	········//·acceptor.·It·remains·open·in·the·parent.
82	········acceptor_.close();
83
84	········//·The·child·process·is·not·interested·in·processing·the·SIGCHLD·signal.
85	········signal_.cancel();
86
87	········start_read();
88	······}
89	······else
90	······{
91	········//·Inform·the·io_context·that·the·fork·is·finished·(or·failed)·and·that
92	········//·this·is·the·parent·process.·The·io_context·uses·this·opportunity·to
93	········//·recreate·any·internal·resources·that·were·cleaned·up·during
94	········//·preparation·for·the·fork.
95	········io_context_.notify_fork(asio::io_context::fork_parent);
96
97	········socket_.close();
98	········start_accept();
99	······}
100	····}
101	····else
102	····{
103	······std::cerr·<<·"Accept·error:·"·<<·ec.message()·<<·std::endl;
104	······start_accept();
105	····}
106	··}
107
108	··void·start_read()
109	··{	115	··{
110	····socket_.async_read_some(asio::buffer(data_),	116	····socket_.async_read_some(asio::buffer(data_),
111	········boost::bind(&server::handle_read,·this,	117	········[this](std::error_code·ec,·std::size_t·length)
112	··········boost::placeholders::_1,·boost::placeholders::_2));	118	········{
		119	··········if·(!ec)
		120	············write(length);
		121	········});
113	··}	122	··}
114		123
115	··void·handle_read(const·asio::error_code&·ec,·std::size_t·length)	124	··void·write(std::size_t·length)
116	··{
117	····if·(!ec)
118	······start_write(length);
119	··}
120
121	··void·start_write(std::size_t·length)
122	··{	125	··{
123	····asio::async_write(socket_,·asio::buffer(data_,·length),	126	····asio::async_write(socket_,·asio::buffer(data_,·length),
124	········boost::bind(&server::handle_write,·this,·boost::placeholders::_1));	127	········[this](std::error_code·ec,·std::size_t·/length/)
125	··}	128	········{
126		129	··········if·(!ec)
127	··void·handle_write(const·asio::error_code&·ec)	130	············read();
128	··{	131	········});
129	····if·(!ec)
130	······start_read();
131	··}	132	··}
132		133
133	··asio::io_context&·io_context_;	134	··asio::io_context&·io_context_;
134	··asio::signal_set·signal_;	135	··asio::signal_set·signal_;
135	··tcp::acceptor·acceptor_;	136	··tcp::acceptor·acceptor_;
136	··tcp::socket·socket_;	137	··tcp::socket·socket_;
137	··boost::array<char,·1024>·data_;	138	··std::array<char,·1024>·data_;
138	};	139	};
139		140
140	int·main(int·argc,·char*·argv[])	141	int·main(int·argc,·char*·argv[])
141	{	142	{
142	··try	143	··try
143	··{	144	··{
144	····if·(argc·!=·2)	145	····if·(argc·!=·2)
145	····{	146	····{
146	······std::cerr·<<·"Usage:·process_per_connection·<port>\n";	147	······std::cerr·<<·"Usage:·process_per_connection·<port>\n";
147	······return·1;	148	······return·1;
148	····}	149	····}
149		150
150	····asio::io_context·io_context;	151	····asio::io_context·io_context;
151		152
152	····using·namespace·std;·//·For·atoi.	153	····using·namespace·std;·//·For·atoi.
153	····server·s(io_context,·atoi(argv[1]));	154	····server·s(io_context,·atoi(argv[1]));
154		155
155	····io_context.run();	156	····io_context.run();
156	··}	157	··}
157	··catch·(std::exception&·e)	158	··catch·(std::exception&·e)
158	··{	159	··{
159	····std::cerr·<<·"Exception:·"·<<·e.what()·<<·std::endl;	160	····std::cerr·<<·"Exception:·"·<<·e.what()·<<·std::endl;
160	··}	161	··}
161	}	162	}