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/* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
/* The purpose of this file is to store the code that MOST mpm's will need
* this does not mean a function only goes into this file if every MPM needs
* it. It means that if a function is needed by more than one MPM, and
* future maintenance would be served by making the code common, then the
* function belongs here.
* This is going in src/main because it is not platform specific, it is
* specific to multi-process servers, but NOT to Unix. Which is why it
* does not belong in src/os/unix
* @file mpm_common.h
* @brief Multi-Processing Modules functions
* @defgroup APACHE_MPM Multi-Processing Modules
* @ingroup APACHE
* @{
#include "ap_config.h"
#include "ap_mpm.h"
#include "scoreboard.h"
#include <netinet/tcp.h> /* for TCP_NODELAY */
#include "apr_proc_mutex.h"
#ifdef __cplusplus
extern "C" {
/* The maximum length of the queue of pending connections, as defined
* by listen(2). Under some systems, it should be increased if you
* are experiencing a heavy TCP SYN flood attack.
* It defaults to 511 instead of 512 because some systems store it
* as an 8-bit datatype; 512 truncated to 8-bits is 0, while 511 is
* 255 when truncated.
/* Signal used to gracefully restart */
/* Signal used to gracefully restart (without SIG prefix) */
/* Signal used to gracefully restart (as a quoted string) */
/* Signal used to gracefully stop */
/* Signal used to gracefully stop (without SIG prefix) */
/* Signal used to gracefully stop (as a quoted string) */
* Callback function used for ap_reclaim_child_processes() and
* ap_relieve_child_processes(). The callback function will be
* called for each terminated child process.
typedef void ap_reclaim_callback_fn_t(int childnum, pid_t pid,
ap_generation_t gen);
#if (!defined(WIN32) && !defined(NETWARE)) || defined(DOXYGEN)
* Make sure all child processes that have been spawned by the parent process
* have died. This includes process registered as "other_children".
* @param terminate Either 1 or 0. If 1, send the child processes SIGTERM
* each time through the loop. If 0, give the process time to die
* on its own before signalling it.
* @param mpm_callback Callback invoked for each dead child process
* @note The MPM child processes which are reclaimed are those listed
* in the scoreboard as well as those currently registered via
* ap_register_extra_mpm_process().
AP_DECLARE(void) ap_reclaim_child_processes(int terminate,
ap_reclaim_callback_fn_t *mpm_callback);
* Catch any child processes that have been spawned by the parent process
* which have exited. This includes processes registered as "other_children".
* @param mpm_callback Callback invoked for each dead child process
* @note The MPM child processes which are relieved are those listed
* in the scoreboard as well as those currently registered via
* ap_register_extra_mpm_process().
AP_DECLARE(void) ap_relieve_child_processes(ap_reclaim_callback_fn_t *mpm_callback);
* Tell ap_reclaim_child_processes() and ap_relieve_child_processes() about
* an MPM child process which has no entry in the scoreboard.
* @param pid The process id of an MPM child process which should be
* reclaimed when ap_reclaim_child_processes() is called.
* @param gen The generation of this MPM child process.
* @note If an extra MPM child process terminates prior to calling
* ap_reclaim_child_processes(), remove it from the list of such processes
* by calling ap_unregister_extra_mpm_process().
AP_DECLARE(void) ap_register_extra_mpm_process(pid_t pid, ap_generation_t gen);
* Unregister an MPM child process which was previously registered by a
* call to ap_register_extra_mpm_process().
* @param pid The process id of an MPM child process which no longer needs to
* be reclaimed.
* @param old_gen Set to the server generation of the process, if found.
* @return 1 if the process was found and removed, 0 otherwise
AP_DECLARE(int) ap_unregister_extra_mpm_process(pid_t pid, ap_generation_t *old_gen);
* Safely signal an MPM child process, if the process is in the
* current process group. Otherwise fail.
* @param pid the process id of a child process to signal
* @param sig the signal number to send
* @return APR_SUCCESS if signal is sent, otherwise an error as per kill(3);
* APR_EINVAL is returned if passed either an invalid (< 1) pid, or if
* the pid is not in the current process group
AP_DECLARE(apr_status_t) ap_mpm_safe_kill(pid_t pid, int sig);
* Log why a child died to the error log, if the child died without the
* parent signalling it.
* @param pid The child that has died
* @param why The return code of the child process
* @param status The status returned from ap_wait_or_timeout
* @return 0 on success, APEXIT_CHILDFATAL if MPM should terminate
AP_DECLARE(int) ap_process_child_status(apr_proc_t *pid, apr_exit_why_e why, int status);
AP_DECLARE(apr_status_t) ap_fatal_signal_setup(server_rec *s, apr_pool_t *in_pconf);
AP_DECLARE(apr_status_t) ap_fatal_signal_child_setup(server_rec *s);
#endif /* (!WIN32 && !NETWARE) || DOXYGEN */
* Pool cleanup for end-generation hook implementation
* (core httpd function)
apr_status_t ap_mpm_end_gen_helper(void *unused);
* Run the monitor hook (once every ten calls), determine if any child
* process has died and, if none died, sleep one second.
* @param status The return code if a process has died
* @param exitcode The returned exit status of the child, if a child process
* dies, or the signal that caused the child to die.
* @param ret The process id of the process that died
* @param p The pool to allocate out of
* @param s The server_rec to pass
AP_DECLARE(void) ap_wait_or_timeout(apr_exit_why_e *status, int *exitcode,
apr_proc_t *ret, apr_pool_t *p,
server_rec *s);
#if defined(TCP_NODELAY)
* Turn off the nagle algorithm for the specified socket. The nagle algorithm
* says that we should delay sending partial packets in the hopes of getting
* more data. There are bad interactions between persistent connections and
* Nagle's algorithm that have severe performance penalties.
* @param s The socket to disable nagle for.
void ap_sock_disable_nagle(apr_socket_t *s);
#define ap_sock_disable_nagle(s) /* NOOP */
* Convert a username to a numeric ID
* @param name The name to convert
* @return The user id corresponding to a name
* @fn uid_t ap_uname2id(const char *name)
AP_DECLARE(uid_t) ap_uname2id(const char *name);
* Convert a group name to a numeric ID
* @param name The name to convert
* @return The group id corresponding to a name
* @fn gid_t ap_gname2id(const char *name)
AP_DECLARE(gid_t) ap_gname2id(const char *name);
* The initgroups() function initializes the group access list by reading the
* group database /etc/group and using all groups of which user is a member.
* The additional group basegid is also added to the list.
* @param name The user name - must be non-NULL
* @param basegid The basegid to add
* @return returns 0 on success
* @fn int initgroups(const char *name, gid_t basegid)
int initgroups(const char *name, gid_t basegid);
#if !defined(WIN32) || defined(DOXYGEN)
typedef struct ap_pod_t ap_pod_t;
struct ap_pod_t {
apr_file_t *pod_in;
apr_file_t *pod_out;
apr_pool_t *p;
* Open the pipe-of-death. The pipe of death is used to tell all child
* processes that it is time to die gracefully.
* @param p The pool to use for allocating the pipe
* @param pod the pipe-of-death that is created.
AP_DECLARE(apr_status_t) ap_mpm_pod_open(apr_pool_t *p, ap_pod_t **pod);
* Check the pipe to determine if the process has been signalled to die.
AP_DECLARE(apr_status_t) ap_mpm_pod_check(ap_pod_t *pod);
* Close the pipe-of-death
* @param pod the pipe-of-death to close.
AP_DECLARE(apr_status_t) ap_mpm_pod_close(ap_pod_t *pod);
* Write data to the pipe-of-death, signalling that one child process
* should die.
* @param pod the pipe-of-death to write to.
AP_DECLARE(apr_status_t) ap_mpm_pod_signal(ap_pod_t *pod);
* Write data to the pipe-of-death, signalling that all child process
* should die.
* @param pod The pipe-of-death to write to.
* @param num The number of child processes to kill
AP_DECLARE(void) ap_mpm_pod_killpg(ap_pod_t *pod, int num);
#endif /* !WIN32 || DOXYGEN */
* Check that exactly one MPM is loaded
* Returns NULL if yes, error string if not.
AP_DECLARE(const char *) ap_check_mpm(void);
* These data members are common to all mpms. Each new mpm
* should either use the appropriate ap_mpm_set_* function
* in their command table or create their own for custom or
* OS specific needs. These should work for most.
* The maximum number of requests each child thread or
* process handles before dying off
AP_DECLARE_DATA extern int ap_max_requests_per_child;
const char *ap_mpm_set_max_requests(cmd_parms *cmd, void *dummy,
const char *arg);
* The filename used to store the process id.
AP_DECLARE_DATA extern const char *ap_pid_fname;
const char *ap_mpm_set_pidfile(cmd_parms *cmd, void *dummy,
const char *arg);
void ap_mpm_dump_pidfile(apr_pool_t *p, apr_file_t *out);
* The directory that the server changes directory to dump core.
AP_DECLARE_DATA extern char ap_coredump_dir[MAX_STRING_LEN];
AP_DECLARE_DATA extern int ap_coredumpdir_configured;
const char *ap_mpm_set_coredumpdir(cmd_parms *cmd, void *dummy,
const char *arg);
* Set the timeout period for a graceful shutdown.
AP_DECLARE_DATA extern int ap_graceful_shutdown_timeout;
AP_DECLARE(const char *)ap_mpm_set_graceful_shutdown(cmd_parms *cmd, void *dummy,
const char *arg);
AP_INIT_TAKE1("GracefulShutdownTimeout", ap_mpm_set_graceful_shutdown, NULL, \
RSRC_CONF, "Maximum time in seconds to wait for child " \
"processes to complete transactions during shutdown")
int ap_signal_server(int *, apr_pool_t *);
void ap_mpm_rewrite_args(process_rec *);
AP_DECLARE_DATA extern apr_uint32_t ap_max_mem_free;
extern const char *ap_mpm_set_max_mem_free(cmd_parms *cmd, void *dummy,
const char *arg);
AP_DECLARE_DATA extern apr_size_t ap_thread_stacksize;
extern const char *ap_mpm_set_thread_stacksize(cmd_parms *cmd, void *dummy,
const char *arg);
/* core's implementation of child_status hook */
extern void ap_core_child_status(server_rec *s, pid_t pid, ap_generation_t gen,
int slot, mpm_child_status status);
extern const char *ap_mpm_set_exception_hook(cmd_parms *cmd, void *dummy,
const char *arg);
AP_DECLARE_HOOK(int,monitor,(apr_pool_t *p, server_rec *s))
/* register modules that undertake to manage system security */
AP_DECLARE(int) ap_sys_privileges_handlers(int inc);
AP_DECLARE_HOOK(int, drop_privileges, (apr_pool_t * pchild, server_rec * s))
/* implement the ap_mpm_query() function
* The MPM should return OK+APR_ENOTIMPL for any unimplemented query codes;
* modules which intercede for specific query codes should DECLINE for others.
AP_DECLARE_HOOK(int, mpm_query, (int query_code, int *result, apr_status_t *rv))
/* register the specified callback */
AP_DECLARE_HOOK(apr_status_t, mpm_register_timed_callback,
(apr_time_t t, ap_mpm_callback_fn_t *cbfn, void *baton))
/* get MPM name (e.g., "prefork" or "event") */
AP_DECLARE_HOOK(const char *,mpm_get_name,(void))
/* mutex type string for accept mutex, if any; MPMs should use the
* same mutex type for ease of configuration
#define AP_ACCEPT_MUTEX_TYPE "mpm-accept"
/* internal pre-config logic for MPM-related settings, callable only from
* core's pre-config hook
void mpm_common_pre_config(apr_pool_t *pconf);
#ifdef __cplusplus
#endif /* !APACHE_MPM_COMMON_H */
/** @} */
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