include/ap_mpm.h - httpd - Git at Google

 /* ====================================================================
  * Copyright (c) 1995-1999 The Apache Group.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  *
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in
  *    the documentation and/or other materials provided with the
  *    distribution.
  *
  * 3. All advertising materials mentioning features or use of this
  *    software must display the following acknowledgment:
  *    "This product includes software developed by the Apache Group
  *    for use in the Apache HTTP server project (http://www.apache.org/)."
  *
  * 4. The names "Apache Server" and "Apache Group" must not be used to
  *    endorse or promote products derived from this software without
  *    prior written permission. For written permission, please contact
  *    apache@apache.org.
  *
  * 5. Products derived from this software may not be called "Apache"
  *    nor may "Apache" appear in their names without prior written
  *    permission of the Apache Group.
  *
  * 6. Redistributions of any form whatsoever must retain the following
  *    acknowledgment:
  *    "This product includes software developed by the Apache Group
  *    for use in the Apache HTTP server project (http://www.apache.org/)."
  *
  * THIS SOFTWARE IS PROVIDED BY THE APACHE GROUP ``AS IS'' AND ANY
  * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE APACHE GROUP OR
  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  * OF THE POSSIBILITY OF SUCH DAMAGE.
  * ====================================================================
  *
  * This software consists of voluntary contributions made by many
  * individuals on behalf of the Apache Group and was originally based
  * on public domain software written at the National Center for
  * Supercomputing Applications, University of Illinois, Urbana-Champaign.
  * For more information on the Apache Group and the Apache HTTP server
  * project, please see <http://www.apache.org/>.
  *
  */

 #ifndef AP_MMN_H
 #define AP_MMN_H

 /*
     The MPM, "multi-processing model" provides an abstraction of the
     interface with the OS for distributing incoming connections to
     threads/process for processing.  http_main invokes the MPM, and
     the MPM runs until a shutdown/restart has been indicated.
     The MPM calls out to the apache core via the ap_process_connection
     function when a connection arrives.

     The MPM may or may not be multithreaded.  In the event that it is
     multithreaded, at any instant it guarantees a 1:1 mapping of threads
     ap_process_connection invocations.

     Note: In the future it will be possible for ap_process_connection
     to return to the MPM prior to finishing the entire connection; and
     the MPM will proceed with asynchronous handling for the connection;
     in the future the MPM may call ap_process_connection again -- but
     does not guarantee it will occur on the same thread as the first call.

     The MPM further guarantees that no asynchronous behaviour such as
     longjmps and signals will interfere with the user code that is
     invoked through ap_process_connection.  The MPM may reserve some
     signals for its use (i.e. SIGUSR1), but guarantees that these signals
     are ignored when executing outside the MPM code itself.  (This
     allows broken user code that does not handle EINTR to function
     properly.)

     The suggested server restart and stop behaviour will be "graceful".
     However the MPM may choose to terminate processes when the user
     requests a non-graceful restart/stop.  When this occurs, the MPM kills
     all threads with extreme prejudice, and destroys the pchild pool.
     User cleanups registered in the pchild ap_context_t will be invoked at
     this point.  (This can pose some complications, the user cleanups
     are asynchronous behaviour not unlike longjmp/signal... but if the
     admin is asking for a non-graceful shutdown, how much effort should
     we put into doing it in a nice way?)

     unix/posix notes:
     - The MPM does not set a SIGALRM handler, user code may use SIGALRM.
 	But the preferred method of handling timeouts is to use the
 	timeouts provided by the BUFF/iol abstraction.
     - The proper setting for SIGPIPE is SIG_IGN, if user code changes it
         for any of their own processing, it must be restored to SIG_IGN
 	prior to executing or returning to any apache code.
     TODO: add SIGPIPE debugging check somewhere to make sure its SIG_IGN
 */

 /* run until a restart/shutdown is indicated, return 1 for shutdown
    0 otherwise */
 API_EXPORT(int) ap_mpm_run(ap_context_t *pconf, ap_context_t *plog, server_rec *server_conf);

 /* predicate indicating if a graceful stop has been requested ...
    used by the connection loop */
 API_EXPORT(int) ap_graceful_stop_signalled(void);

 /*
  * ap_start_shutdown() and ap_start_restart() are functions to initiate
  * shutdown or restart without relying on signals.
  *
  * These should only be called from the parent process itself, since the
  * parent process will use the shutdown_pending and restart_pending variables
  * to determine whether to shutdown or restart. The child process should
  * call signal_parent() directly to tell the parent to die -- this will
  * cause neither of those variable to be set, which the parent will
  * assume means something serious is wrong (which it will be, for the
  * child to force an exit) and so do an exit anyway.
  */

 void ap_start_shutdown(void);
 void ap_start_restart(int graceful);

 /*
  * ap_signal_parent() - used to send a signal to the parent process.
  */
 void ap_signal_parent(ap_context_t *p, const char* signal, const char* server_root);

 #ifdef HAS_OTHER_CHILD
 /*
  * register an other_child -- a child which the main loop keeps track of
  * and knows it is different than the rest of the scoreboard.
  *
  * pid is the pid of the child.
  *
  * maintenance is a function that is invoked with a reason, the data
  * pointer passed here, and when appropriate a status result from waitpid().
  *
  * write_fd is an fd that is probed for writing by select() if it is ever
  * unwritable, then maintenance is invoked with reason OC_REASON_UNWRITABLE.
  * This is useful for log pipe children, to know when they've blocked.  To
  * disable this feature, use -1 for write_fd.
  */
 API_EXPORT(void) ap_register_other_child(int pid,
        void (*maintenance) (int reason, void *data, ap_wait_t status), void *data,
 				      int write_fd);
 #define OC_REASON_DEATH		0	/* child has died, caller must call
 					 * unregister still */
 #define OC_REASON_UNWRITABLE	1	/* write_fd is unwritable */
 #define OC_REASON_RESTART	2	/* a restart is occuring, perform
 					 * any necessary cleanup (including
 					 * sending a special signal to child)
 					 */
 #define OC_REASON_UNREGISTER	3	/* unregister has been called, do
 					 * whatever is necessary (including
 					 * kill the child) */
 #define OC_REASON_LOST		4	/* somehow the child exited without
 					 * us knowing ... buggy os? */

 /*
  * unregister an other_child.  Note that the data pointer is used here, and
  * is assumed to be unique per other_child.  This is because the pid and
  * write_fd are possibly killed off separately.
  */
 API_EXPORT(void) ap_unregister_other_child(void *data);

 #endif

 #endif
	/* ====================================================================
	* Copyright (c) 1995-1999 The Apache Group. All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	*
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	*
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in
	* the documentation and/or other materials provided with the
	* distribution.
	*
	* 3. All advertising materials mentioning features or use of this
	* software must display the following acknowledgment:
	* "This product includes software developed by the Apache Group
	* for use in the Apache HTTP server project (http://www.apache.org/)."
	*
	* 4. The names "Apache Server" and "Apache Group" must not be used to
	* endorse or promote products derived from this software without
	* prior written permission. For written permission, please contact
	* apache@apache.org.
	*
	* 5. Products derived from this software may not be called "Apache"
	* nor may "Apache" appear in their names without prior written
	* permission of the Apache Group.
	*
	* 6. Redistributions of any form whatsoever must retain the following
	* acknowledgment:
	* "This product includes software developed by the Apache Group
	* for use in the Apache HTTP server project (http://www.apache.org/)."
	*
	* THIS SOFTWARE IS PROVIDED BY THE APACHE GROUP ``AS IS'' AND ANY
	* EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
	* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE APACHE GROUP OR
	* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
	* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
	* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
	* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
	* OF THE POSSIBILITY OF SUCH DAMAGE.
	* ====================================================================
	*
	* This software consists of voluntary contributions made by many
	* individuals on behalf of the Apache Group and was originally based
	* on public domain software written at the National Center for
	* Supercomputing Applications, University of Illinois, Urbana-Champaign.
	* For more information on the Apache Group and the Apache HTTP server
	* project, please see <http://www.apache.org/>.
	*
	*/

	#ifndef AP_MMN_H
	#define AP_MMN_H

	/*
	The MPM, "multi-processing model" provides an abstraction of the
	interface with the OS for distributing incoming connections to
	threads/process for processing. http_main invokes the MPM, and
	the MPM runs until a shutdown/restart has been indicated.
	The MPM calls out to the apache core via the ap_process_connection
	function when a connection arrives.

	The MPM may or may not be multithreaded. In the event that it is
	multithreaded, at any instant it guarantees a 1:1 mapping of threads
	ap_process_connection invocations.

	Note: In the future it will be possible for ap_process_connection
	to return to the MPM prior to finishing the entire connection; and
	the MPM will proceed with asynchronous handling for the connection;
	in the future the MPM may call ap_process_connection again -- but
	does not guarantee it will occur on the same thread as the first call.

	The MPM further guarantees that no asynchronous behaviour such as
	longjmps and signals will interfere with the user code that is
	invoked through ap_process_connection. The MPM may reserve some
	signals for its use (i.e. SIGUSR1), but guarantees that these signals
	are ignored when executing outside the MPM code itself. (This
	allows broken user code that does not handle EINTR to function
	properly.)

	The suggested server restart and stop behaviour will be "graceful".
	However the MPM may choose to terminate processes when the user
	requests a non-graceful restart/stop. When this occurs, the MPM kills
	all threads with extreme prejudice, and destroys the pchild pool.
	User cleanups registered in the pchild ap_context_t will be invoked at
	this point. (This can pose some complications, the user cleanups
	are asynchronous behaviour not unlike longjmp/signal... but if the
	admin is asking for a non-graceful shutdown, how much effort should
	we put into doing it in a nice way?)

	unix/posix notes:
	- The MPM does not set a SIGALRM handler, user code may use SIGALRM.
	But the preferred method of handling timeouts is to use the
	timeouts provided by the BUFF/iol abstraction.
	- The proper setting for SIGPIPE is SIG_IGN, if user code changes it
	for any of their own processing, it must be restored to SIG_IGN
	prior to executing or returning to any apache code.
	TODO: add SIGPIPE debugging check somewhere to make sure its SIG_IGN
	*/

	/* run until a restart/shutdown is indicated, return 1 for shutdown
	0 otherwise */
	API_EXPORT(int) ap_mpm_run(ap_context_t pconf, ap_context_t plog, server_rec *server_conf);

	/* predicate indicating if a graceful stop has been requested ...
	used by the connection loop */
	API_EXPORT(int) ap_graceful_stop_signalled(void);

	/*
	* ap_start_shutdown() and ap_start_restart() are functions to initiate
	* shutdown or restart without relying on signals.
	*
	* These should only be called from the parent process itself, since the
	* parent process will use the shutdown_pending and restart_pending variables
	* to determine whether to shutdown or restart. The child process should
	* call signal_parent() directly to tell the parent to die -- this will
	* cause neither of those variable to be set, which the parent will
	* assume means something serious is wrong (which it will be, for the
	* child to force an exit) and so do an exit anyway.
	*/

	void ap_start_shutdown(void);
	void ap_start_restart(int graceful);

	/*
	* ap_signal_parent() - used to send a signal to the parent process.
	*/
	void ap_signal_parent(ap_context_t p, const char signal, const char* server_root);

	#ifdef HAS_OTHER_CHILD
	/*
	* register an other_child -- a child which the main loop keeps track of
	* and knows it is different than the rest of the scoreboard.
	*
	* pid is the pid of the child.
	*
	* maintenance is a function that is invoked with a reason, the data
	* pointer passed here, and when appropriate a status result from waitpid().
	*
	* write_fd is an fd that is probed for writing by select() if it is ever
	* unwritable, then maintenance is invoked with reason OC_REASON_UNWRITABLE.
	* This is useful for log pipe children, to know when they've blocked. To
	* disable this feature, use -1 for write_fd.
	*/
	API_EXPORT(void) ap_register_other_child(int pid,
	void (maintenance) (int reason, void data, ap_wait_t status), void *data,
	int write_fd);
	#define OC_REASON_DEATH 0 /* child has died, caller must call
	* unregister still */
	#define OC_REASON_UNWRITABLE 1 /* write_fd is unwritable */
	#define OC_REASON_RESTART 2 /* a restart is occuring, perform
	* any necessary cleanup (including
	* sending a special signal to child)
	*/
	#define OC_REASON_UNREGISTER 3 /* unregister has been called, do
	* whatever is necessary (including
	* kill the child) */
	#define OC_REASON_LOST 4 /* somehow the child exited without
	* us knowing ... buggy os? */

	/*
	* unregister an other_child. Note that the data pointer is used here, and
	* is assumed to be unique per other_child. This is because the pid and
	* write_fd are possibly killed off separately.
	*/
	API_EXPORT(void) ap_unregister_other_child(void *data);

	#endif

	#endif