1 /* Licensed to the Apache Software Foundation (ASF) under one or more
2 * contributor license agreements. See the NOTICE file distributed with
3 * this work for additional information regarding copyright ownership.
4 * The ASF licenses this file to You under the Apache License, Version 2.0
5 * (the "License"); you may not use this file except in compliance with
6 * the License. You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
19 * @brief Apache Multi-Processing Module library
21 * @defgroup APACHE_CORE_MPM Multi-Processing Module library
22 * @ingroup APACHE_CORE
29 #include "apr_thread_proc.h"
31 #include "scoreboard.h"
38 The MPM, "multi-processing model" provides an abstraction of the
39 interface with the OS for distributing incoming connections to
40 threads/process for processing. http_main invokes the MPM, and
41 the MPM runs until a shutdown/restart has been indicated.
42 The MPM calls out to the apache core via the ap_process_connection
43 function when a connection arrives.
45 The MPM may or may not be multithreaded. In the event that it is
46 multithreaded, at any instant it guarantees a 1:1 mapping of threads
47 ap_process_connection invocations.
49 Note: In the future it will be possible for ap_process_connection
50 to return to the MPM prior to finishing the entire connection; and
51 the MPM will proceed with asynchronous handling for the connection;
52 in the future the MPM may call ap_process_connection again -- but
53 does not guarantee it will occur on the same thread as the first call.
55 The MPM further guarantees that no asynchronous behaviour such as
56 longjmps and signals will interfere with the user code that is
57 invoked through ap_process_connection. The MPM may reserve some
58 signals for its use (i.e. SIGUSR1), but guarantees that these signals
59 are ignored when executing outside the MPM code itself. (This
60 allows broken user code that does not handle EINTR to function
63 The suggested server restart and stop behaviour will be "graceful".
64 However the MPM may choose to terminate processes when the user
65 requests a non-graceful restart/stop. When this occurs, the MPM kills
66 all threads with extreme prejudice, and destroys the pchild pool.
67 User cleanups registered in the pchild apr_pool_t will be invoked at
68 this point. (This can pose some complications, the user cleanups
69 are asynchronous behaviour not unlike longjmp/signal... but if the
70 admin is asking for a non-graceful shutdown, how much effort should
71 we put into doing it in a nice way?)
74 - The MPM does not set a SIGALRM handler, user code may use SIGALRM.
75 But the preferred method of handling timeouts is to use the
76 timeouts provided by the BUFF abstraction.
77 - The proper setting for SIGPIPE is SIG_IGN, if user code changes it
78 for any of their own processing, it must be restored to SIG_IGN
79 prior to executing or returning to any apache code.
80 TODO: add SIGPIPE debugging check somewhere to make sure it's SIG_IGN
84 * Pass control to the MPM for steady-state processing. It is responsible
85 * for controlling the parent and child processes. It will run until a
86 * restart/shutdown is indicated.
87 * @param pconf the configuration pool, reset before the config file is read
88 * @param plog the log pool, reset after the config file is read
89 * @param server_conf the global server config.
90 * @return DONE for shutdown OK otherwise.
93 AP_DECLARE_HOOK(int, mpm, (apr_pool_t *pconf, apr_pool_t *plog, server_rec *server_conf))
96 * Spawn a process with privileges that another module has requested
97 * @param r The request_rec of the current request
98 * @param newproc The resulting process handle.
99 * @param progname The program to run
100 * @param args the arguments to pass to the new program. The first
101 * one should be the program name.
102 * @param env The new environment apr_table_t for the new process. This
103 * should be a list of NULL-terminated strings.
104 * @param attr the procattr we should use to determine how to create the new
106 * @param p The pool to use.
108 AP_DECLARE(apr_status_t) ap_os_create_privileged_process(
109 const request_rec *r,
111 const char *progname,
112 const char * const *args,
113 const char * const *env,
114 apr_procattr_t *attr,
117 /** @defgroup mpmq MPM query
121 /** @defgroup thrdfrk Subtypes/Values returned for AP_MPMQ_IS_THREADED and AP_MPMQ_IS_FORKED
125 #define AP_MPMQ_NOT_SUPPORTED 0 /**< This value specifies that an
126 * MPM is not capable of
127 * threading or forking. */
128 #define AP_MPMQ_STATIC 1 /**< This value specifies that
129 * an MPM is using a static
130 * number of threads or daemons */
131 #define AP_MPMQ_DYNAMIC 2 /**< This value specifies that
132 * an MPM is using a dynamic
133 * number of threads or daemons */
136 /** @defgroup qstate Values returned for AP_MPMQ_MPM_STATE
140 #define AP_MPMQ_STARTING 0
141 #define AP_MPMQ_RUNNING 1
142 #define AP_MPMQ_STOPPING 2
145 /** @defgroup qcodes Query codes for ap_mpm_query()
149 /** Max # of daemons used so far */
150 #define AP_MPMQ_MAX_DAEMON_USED 1
151 /** MPM can do threading */
152 #define AP_MPMQ_IS_THREADED 2
153 /** MPM can do forking */
154 #define AP_MPMQ_IS_FORKED 3
155 /** The compiled max # daemons */
156 #define AP_MPMQ_HARD_LIMIT_DAEMONS 4
157 /** The compiled max # threads */
158 #define AP_MPMQ_HARD_LIMIT_THREADS 5
159 /** \# of threads/child by config */
160 #define AP_MPMQ_MAX_THREADS 6
161 /** Min # of spare daemons */
162 #define AP_MPMQ_MIN_SPARE_DAEMONS 7
163 /** Min # of spare threads */
164 #define AP_MPMQ_MIN_SPARE_THREADS 8
165 /** Max # of spare daemons */
166 #define AP_MPMQ_MAX_SPARE_DAEMONS 9
167 /** Max # of spare threads */
168 #define AP_MPMQ_MAX_SPARE_THREADS 10
169 /** Max # of requests per daemon */
170 #define AP_MPMQ_MAX_REQUESTS_DAEMON 11
171 /** Max # of daemons by config */
172 #define AP_MPMQ_MAX_DAEMONS 12
173 /** starting, running, stopping */
174 #define AP_MPMQ_MPM_STATE 13
175 /** MPM can process async connections */
176 #define AP_MPMQ_IS_ASYNC 14
177 /** MPM generation */
178 #define AP_MPMQ_GENERATION 15
179 /** MPM can drive serf internally */
180 #define AP_MPMQ_HAS_SERF 16
181 /** MPM supports suspending/resuming connections */
182 #define AP_MPMQ_CAN_SUSPEND 17
186 * Query a property of the current MPM.
187 * @param query_code One of AP_MPMQ_*
188 * @param result A location to place the result of the query
189 * @return APR_EGENERAL if an mpm-query hook has not been registered;
190 * APR_SUCCESS or APR_ENOTIMPL otherwise
191 * @remark The MPM doesn't register the implementing hook until the
192 * register_hooks hook is called, so modules cannot use ap_mpm_query()
193 * until after that point.
194 * @fn int ap_mpm_query(int query_code, int *result)
196 AP_DECLARE(apr_status_t) ap_mpm_query(int query_code, int *result);
200 typedef void (ap_mpm_callback_fn_t)(void *baton);
202 /* only added support in the Event MPM.... check for APR_ENOTIMPL */
203 AP_DECLARE(apr_status_t) ap_mpm_resume_suspended(conn_rec *c);
204 /* only added support in the Event MPM.... check for APR_ENOTIMPL */
205 AP_DECLARE(apr_status_t) ap_mpm_register_timed_callback(apr_time_t t,
206 ap_mpm_callback_fn_t *cbfn,
210 * Register a callback on the readability or writability on a group of sockets
211 * @param s Null-terminated list of sockets
212 * @param p pool for use between registration and callback
213 * @param for_read Whether the sockets are monitored for read or writability
214 * @param cbfn The callback function
215 * @param baton userdata for the callback function
216 * @return APR_SUCCESS if all sockets could be added to a pollset,
217 * APR_ENOTIMPL if no asynch support, or an apr_pollset_add error.
218 * @remark When activity is found on any 1 socket in the list, all are removed
219 * from the pollset and only 1 callback is issued.
222 AP_DECLARE(apr_status_t) ap_mpm_register_socket_callback(apr_socket_t **s,
225 ap_mpm_callback_fn_t *cbfn,
228 * Register a callback on the readability or writability on a group of sockets, with a timeout
229 * @param s Null-terminated list of sockets
230 * @param p pool for use between registration and callback
231 * @param for_read Whether the sockets are monitored for read or writability
232 * @param cbfn The callback function
233 * @param tofn The callback function if the timeout expires
234 * @param baton userdata for the callback function
235 * @param timeout timeout for I/O in microseconds, unlimited if <= 0
236 * @return APR_SUCCESS if all sockets could be added to a pollset,
237 * APR_ENOTIMPL if no asynch support, or an apr_pollset_add error.
238 * @remark When activity is found on any 1 socket in the list, all are removed
239 * from the pollset and only 1 callback is issued.
240 * @remark For each call, only one of tofn or cbfn will be called, never both.
243 AP_DECLARE(apr_status_t) ap_mpm_register_socket_callback_timeout(apr_socket_t **s,
246 ap_mpm_callback_fn_t *cbfn,
247 ap_mpm_callback_fn_t *tofn,
252 AP_DECLARE(apr_status_t) ap_mpm_unregister_socket_callback(apr_socket_t **s,
255 typedef enum mpm_child_status {
262 * Allow a module to remain aware of MPM child process state changes,
263 * along with the generation and scoreboard slot of the process changing
266 * With some MPMs (event and worker), an active MPM child process may lose
267 * its scoreboard slot if the child process is exiting and the scoreboard
268 * slot is needed by other processes. When this occurs, the hook will be
269 * called with the MPM_CHILD_LOST_SLOT state.
271 * @param s The main server_rec.
272 * @param pid The id of the MPM child process.
273 * @param gen The server generation of that child process.
274 * @param slot The scoreboard slot number, or -1. It will be -1 when an
275 * MPM child process exits, and that child had previously lost its
277 * @param state One of the mpm_child_status values. Modules should ignore
278 * unrecognized values.
281 AP_DECLARE_HOOK(void,child_status,(server_rec *s, pid_t pid, ap_generation_t gen,
282 int slot, mpm_child_status state))
285 * Allow a module to be notified when the last child process of a generation
288 * @param s The main server_rec.
289 * @param gen The server generation which is now completely finished.
292 AP_DECLARE_HOOK(void,end_generation,(server_rec *s, ap_generation_t gen))
294 /* Defining GPROF when compiling uses the moncontrol() function to
295 * disable gprof profiling in the parent, and enable it only for
296 * request processing in children (or in one_process mode). It's
297 * absolutely required to get useful gprof results under linux
298 * because the profile itimers and such are disabled across a
299 * fork(). It's probably useful elsewhere as well.
302 extern void moncontrol(int);
303 #define AP_MONCONTROL(x) moncontrol(x)
305 #define AP_MONCONTROL(x)
308 #ifdef AP_ENABLE_EXCEPTION_HOOK
309 typedef struct ap_exception_info_t {
312 } ap_exception_info_t;
315 * Run the fatal_exception hook for each module; this hook is run
316 * from some MPMs in the event of a child process crash, if the
317 * server was built with --enable-exception-hook and the
318 * EnableExceptionHook directive is On.
319 * @param ei information about the exception
322 AP_DECLARE_HOOK(int,fatal_exception,(ap_exception_info_t *ei))
323 #endif /*AP_ENABLE_EXCEPTION_HOOK*/