perchild.c

Apache 2.0.63 is the current stable version of the 2.0 series, and is recommended over any previous

/* 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
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "apr_hash.h"
#include "apr_strings.h"
#include "apr_pools.h"
#include "apr_portable.h"
#include "apr_file_io.h"
#include "apr_signal.h"

#define APR_WANT_IOVEC
#include "apr_want.h"

#if APR_HAVE_UNISTD_H
#include <unistd.h>
#endif
#if APR_HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif

#if !APR_HAS_THREADS
#error The perchild MPM requires APR threads, but they are unavailable.
#endif  

#define CORE_PRIVATE 
 
#include "ap_config.h"
#include "httpd.h" 
#include "http_main.h" 
#include "http_log.h" 
#include "http_config.h"    /* for read_config */ 
#include "http_core.h"      /* for get_remote_host */ 
#include "http_protocol.h"
#include "http_connection.h"
#include "ap_mpm.h"
#include "unixd.h"
#include "mpm_common.h"
#include "ap_listen.h"
#include "mpm_default.h"
#include "mpm.h"
#include "scoreboard.h"
#include "util_filter.h"
#include "apr_poll.h"

#ifdef HAVE_POLL_H
#include <poll.h>
#endif
#ifdef HAVE_SYS_POLL_H
#include <sys/poll.h>
#endif

/* ### should be APR-ized */
#include <grp.h>
#include <pwd.h>
#include <sys/stat.h>
#include <sys/un.h>
#include <setjmp.h>
#ifdef HAVE_SYS_PROCESSOR_H
#include <sys/processor.h> /* for bindprocessor() */
#endif

/*
 * Define some magic numbers that we use for the state of the incomming
 * request. These must be < 0 so they don't collide with a file descriptor.
 */
#define AP_PERCHILD_THISCHILD -1
#define AP_PERCHILD_OTHERCHILD -2

/* Limit on the threads per process.  Clients will be locked out if more than
 * this * server_limit are needed.
 *
 * We keep this for one reason it keeps the size of the scoreboard file small
 * enough that we can read the whole thing without worrying too much about
 * the overhead.
 */
#ifndef DEFAULT_THREAD_LIMIT
#define DEFAULT_THREAD_LIMIT 64 
#endif

/* Admin can't tune ThreadLimit beyond MAX_THREAD_LIMIT.  We want
 * some sort of compile-time limit to help catch typos.
 */
#ifndef MAX_THREAD_LIMIT
#define MAX_THREAD_LIMIT 20000
#endif 

/* Limit on the total --- clients will be locked out if more servers than
 * this are needed.  It is intended solely to keep the server from crashing
 * when things get out of hand.
 *
 * We keep a hard maximum number of servers, for two reasons --- first off,
 * in case something goes seriously wrong, we want to stop the fork bomb
 * short of actually crashing the machine we're running on by filling some
 * kernel table.  Secondly, it keeps the size of the scoreboard file small
 * enough that we can read the whole thing without worrying too much about
 * the overhead.
 */
#ifndef DEFAULT_SERVER_LIMIT
#define DEFAULT_SERVER_LIMIT 8 
#endif

/* Admin can't tune ServerLimit beyond MAX_SERVER_LIMIT.  We want
 * some sort of compile-time limit to help catch typos.
 */
#ifndef MAX_SERVER_LIMIT
#define MAX_SERVER_LIMIT 20000
#endif

/*
 * Actual definitions of config globals
 */

static int threads_to_start = 0;         /* Worker threads per child */
static int min_spare_threads = 0;
static int max_spare_threads = 0;
static int max_threads = 0;
static int server_limit = DEFAULT_SERVER_LIMIT;
static int first_server_limit;
static int thread_limit = DEFAULT_THREAD_LIMIT;
static int first_thread_limit;
static int changed_limit_at_restart;
static int num_daemons = 0;
static int curr_child_num = 0;
static int workers_may_exit = 0;
static int requests_this_child;
static int num_listensocks = 0;
static ap_pod_t *pod;
static jmp_buf jmpbuffer;

struct child_info_t {
    uid_t uid;
    gid_t gid;
    int input;       /* The socket descriptor */
    int output;      /* The socket descriptor */
};

typedef struct {
    const char *sockname;       /* The base name for the socket */
    const char *fullsockname;   /* socket base name + extension */
    int        input;           /* The socket descriptor */
    int        output;          /* The socket descriptor */
} perchild_server_conf;

typedef struct child_info_t child_info_t;

/* Tables used to determine the user and group each child process should
 * run as.  The hash table is used to correlate a server name with a child
 * process.
 */
static child_info_t *child_info_table;
static int          *thread_socket_table;
struct ap_ctable    *ap_child_table;

/*
 * The max child slot ever assigned, preserved across restarts.  Necessary
 * to deal with NumServers changes across AP_SIG_GRACEFUL restarts.  We 
 * use this value to optimize routines that have to scan the entire child 
 * table.
 *
 * XXX - It might not be worth keeping this code in. There aren't very
 * many child processes in this MPM.
 */
int ap_max_daemons_limit = -1;
int ap_threads_per_child; /* XXX not part of API!  axe it! */

module AP_MODULE_DECLARE_DATA mpm_perchild_module;

static apr_file_t *pipe_of_death_in = NULL;
static apr_file_t *pipe_of_death_out = NULL;
static apr_thread_mutex_t *pipe_of_death_mutex;

/* *Non*-shared http_main globals... */

server_rec *ap_server_conf;

/* one_process --- debugging mode variable; can be set from the command line
 * with the -X flag.  If set, this gets you the child_main loop running
 * in the process which originally started up (no detach, no make_child),
 * which is a pretty nice debugging environment.  (You'll get a SIGHUP
 * early in standalone_main; just continue through.  This is the server
 * trying to kill off any child processes which it might have lying
 * around --- Apache doesn't keep track of their pids, it just sends
 * SIGHUP to the process group, ignoring it in the root process.
 * Continue through and you'll be fine.).
 */

static int one_process = 0;

#ifdef DEBUG_SIGSTOP
int raise_sigstop_flags;
#endif

static apr_pool_t *pconf;              /* Pool for config stuff */
static apr_pool_t *pchild;             /* Pool for httpd child stuff */
static apr_pool_t *thread_pool_parent; /* Parent of per-thread pools */
static apr_thread_mutex_t *thread_pool_parent_mutex;

static int child_num;
static unsigned int my_pid; /* Linux getpid() doesn't work except in 
                      main thread. Use this instead */
/* Keep track of the number of worker threads currently active */
static int worker_thread_count;
static apr_thread_mutex_t *worker_thread_count_mutex;
static int *worker_thread_free_ids;
static apr_threadattr_t *worker_thread_attr;

/* Keep track of the number of idle worker threads */
static int idle_thread_count;
static apr_thread_mutex_t *idle_thread_count_mutex;

/* Locks for accept serialization */
#ifdef NO_SERIALIZED_ACCEPT
#define SAFE_ACCEPT(stmt) APR_SUCCESS
#else
#define SAFE_ACCEPT(stmt) (stmt)
static apr_proc_mutex_t *process_accept_mutex;
#endif /* NO_SERIALIZED_ACCEPT */
static apr_thread_mutex_t *thread_accept_mutex;

AP_DECLARE(apr_status_t) ap_mpm_query(int query_code, int *result)
{
    switch(query_code){
        case AP_MPMQ_MAX_DAEMON_USED:
            *result = ap_max_daemons_limit;
            return APR_SUCCESS;
        case AP_MPMQ_IS_THREADED:
            *result = AP_MPMQ_DYNAMIC;
            return APR_SUCCESS;
        case AP_MPMQ_IS_FORKED:
            *result = AP_MPMQ_STATIC;
            return APR_SUCCESS;
        case AP_MPMQ_HARD_LIMIT_DAEMONS:
            *result = server_limit;
            return APR_SUCCESS;
        case AP_MPMQ_HARD_LIMIT_THREADS:
            *result = thread_limit;
            return APR_SUCCESS;
        case AP_MPMQ_MAX_THREADS:
            *result = max_threads;
            return APR_SUCCESS;
        case AP_MPMQ_MIN_SPARE_DAEMONS:
            *result = 0;
            return APR_SUCCESS;
        case AP_MPMQ_MIN_SPARE_THREADS:    
            *result = min_spare_threads;
            return APR_SUCCESS;
        case AP_MPMQ_MAX_SPARE_DAEMONS:
            *result = 0;
            return APR_SUCCESS;
        case AP_MPMQ_MAX_SPARE_THREADS:
            *result = max_spare_threads;
            return APR_SUCCESS;
        case AP_MPMQ_MAX_REQUESTS_DAEMON:
            *result = ap_max_requests_per_child;
            return APR_SUCCESS; 
        case AP_MPMQ_MAX_DAEMONS:
            *result = num_daemons;
            return APR_SUCCESS;
    }
    return APR_ENOTIMPL;
}

/* a clean exit from a child with proper cleanup */
static void clean_child_exit(int code)
{
    if (pchild) {
        apr_pool_destroy(pchild);
    }
    exit(code);
}

static void just_die(int sig)
{
    clean_child_exit(0);
}

/*****************************************************************
 * Connection structures and accounting...
 */

/* volatile just in case */
static int volatile shutdown_pending;
static int volatile restart_pending;
static int volatile is_graceful;
static int volatile child_fatal;
/* we don't currently track ap_my_generation, but mod_status 
 * references it so it must be defined */
ap_generation_t volatile ap_my_generation=0;

/*
 * ap_start_shutdown() and ap_start_restart(), below, are a first stab at
 * functions to initiate shutdown or restart without relying on signals. 
 * Previously this was initiated in sig_term() and restart() signal handlers, 
 * but we want to be able to start a shutdown/restart from other sources --
 * e.g. on Win32, from the service manager. Now the service manager can
 * call ap_start_shutdown() or ap_start_restart() as appropiate.  Note that
 * these functions can also be called by the child processes, since global
 * variables are no longer used to pass on the required action to the parent.
 *
 * 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.
 */

static void ap_start_shutdown(void)
{
    if (shutdown_pending == 1) {
        /* Um, is this _probably_ not an error, if the user has
         * tried to do a shutdown twice quickly, so we won't
         * worry about reporting it.
         */
        return;
    }
    shutdown_pending = 1;
}

/* do a graceful restart if graceful == 1 */
static void ap_start_restart(int graceful)
{

    if (restart_pending == 1) {
        /* Probably not an error - don't bother reporting it */
        return;
    }
    restart_pending = 1;
    is_graceful = graceful;
}

static void sig_term(int sig)
{
    ap_start_shutdown();
}

static void restart(int sig)
{
#ifndef WIN32
    ap_start_restart(sig == AP_SIG_GRACEFUL);
#else
    ap_start_restart(1);
#endif
}

static void set_signals(void)
{
#ifndef NO_USE_SIGACTION
    struct sigaction sa;
#endif

    if (!one_process) {
        ap_fatal_signal_setup(ap_server_conf, pconf);
    }

#ifndef NO_USE_SIGACTION
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = 0;

    sa.sa_handler = sig_term;
    if (sigaction(SIGTERM, &sa, NULL) < 0)
        ap_log_error(APLOG_MARK, APLOG_WARNING, errno, ap_server_conf,
                     "sigaction(SIGTERM)");
#ifdef SIGINT
    if (sigaction(SIGINT, &sa, NULL) < 0)
        ap_log_error(APLOG_MARK, APLOG_WARNING, errno, ap_server_conf,
                     "sigaction(SIGINT)");
#endif