Commit fb449146 authored by Ryan Bloom's avatar Ryan Bloom
Browse files

First pass at the pipe_of_death logic for the prefork MPM. This does 

pass some initial testing, but it needs to be banged on more.  It looks
like if the server gets a lot of requests to restart all at once, there
are potential problems, but other than that this does seem to solve our
current restart issues.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@89282 13f79535-47bb-0310-9956-ffa450edef68
parent da4e6658

include/httpd.h

+2 −0
Original line number Diff line number Diff line
@@ -1542,6 +1542,8 @@ const char *ap_strstr_c(const char *s, const char *c); 


#endif



#define AP_NORESTART		APR_OS_START_USEERR + 1



#ifdef __cplusplus

}

#endif

include/mpm_common.h

+43 −0
Original line number Diff line number Diff line
@@ -164,6 +164,49 @@ AP_DECLARE(gid_t) ap_gname2id(const char *name); 


#define AP_MPM_HARD_LIMITS_FILE APACHE_MPM_DIR "/mpm_default.h"



#ifdef AP_MPM_USES_POD



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

 */

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

 */

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 p The pool to use when allocating any required structures.

 */

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 p The pool to use when allocating any required structures.

 * @param num The number of child processes to kill

 */

AP_DECLARE(void) ap_mpm_pod_killpg(ap_pod_t *pod, int num);

#endif



#ifdef __cplusplus

}

#endif

server/mpm/prefork/mpm.h

+1 −0
Original line number Diff line number Diff line
@@ -68,6 +68,7 @@ 


#define MPM_NAME "Prefork"



#define AP_MPM_USES_POD 1

#define AP_MPM_NEEDS_RECLAIM_CHILD_PROCESSES 1

#define MPM_SYNC_CHILD_TABLE() (ap_sync_scoreboard_image())

#define MPM_CHILD_PID(i) (ap_scoreboard_image->parent[i].pid)

server/mpm/prefork/prefork.c

+31 −36
Original line number Diff line number Diff line
@@ -140,6 +140,8 @@ static int ap_daemons_min_free=0; 
static int ap_daemons_max_free=0;

static int ap_daemons_limit=0;



static ap_pod_t *pod;



/*

 * The max child slot ever assigned, preserved across restarts.  Necessary

 * to deal with MaxClients changes across SIGWINCH restarts.  We use this
@@ -182,6 +184,8 @@ int tpf_child = 0; 
char tpf_server_name[INETD_SERVNAME_LENGTH+1];

#endif /* TPF */



int die_now = 0;



#ifdef GPROF

/* 

 * change directory for gprof to plop the gmon.out file
@@ -232,7 +236,7 @@ static void clean_child_exit(int code) 
    if (pchild) {

	apr_pool_destroy(pchild);

    }

    ap_scoreboard_image->parent[my_child_num].process_status = SB_WORKING;

    ap_mpm_pod_close(pod);

    chdir_for_gprof();

    exit(code);

}
@@ -378,15 +382,7 @@ static void just_die(int sig) 
static void please_die_gracefully(int sig)

{

    /* clean_child_exit(0); */

    ap_scoreboard_image->parent[my_child_num].process_status = SB_IDLE_DIE;

    if (sig == SIGHUP) {

        (void) ap_update_child_status(AP_CHILD_THREAD_FROM_ID(my_child_num),

                                      SERVER_GRACEFUL, (request_rec *) NULL);

    }

    else {

        (void) ap_update_child_status(AP_CHILD_THREAD_FROM_ID(my_child_num),

                                      SERVER_IDLE_KILL, (request_rec *) NULL);

    }

    die_now = 1;

}



/* volatile just in case */
@@ -414,9 +410,11 @@ static void restart(int sig) 
	return;

    }

    restart_pending = 1;

#if 0

    if ((is_graceful = (sig == SIGWINCH))) {

        apr_pool_cleanup_kill(pconf, NULL, ap_cleanup_scoreboard);

    }

#endif

}



static void set_signals(void)
@@ -479,12 +477,9 @@ static void set_signals(void) 


    /* we want to ignore HUPs and WINCH while we're busy processing one */

    sigaddset(&sa.sa_mask, SIGHUP);

    sigaddset(&sa.sa_mask, SIGWINCH);

    sa.sa_handler = restart;

    if (sigaction(SIGHUP, &sa, NULL) < 0)

	ap_log_error(APLOG_MARK, APLOG_WARNING, errno, ap_server_conf, "sigaction(SIGHUP)");

    if (sigaction(SIGWINCH, &sa, NULL) < 0)

	ap_log_error(APLOG_MARK, APLOG_WARNING, errno, ap_server_conf, "sigaction(SIGWINCH)");

#else

    if (!one_process) {

	apr_signal(SIGSEGV, sig_coredump);
@@ -513,7 +508,7 @@ static void set_signals(void) 
    apr_signal(SIGHUP, restart);

#endif /* SIGHUP */

#ifdef SIGWINCH

    apr_signal(SIGWINCH, restart);

    apr_signal(SIGWINCH, SIG_IGN);

#endif /* SIGWINCH */

#ifdef SIGPIPE

    apr_signal(SIGPIPE, SIG_IGN);
@@ -533,9 +528,6 @@ static apr_socket_t *csd; 
static int requests_this_child;

static fd_set main_fds;



#define I_AM_TO_SHUTDOWN()                                                   \

(ap_scoreboard_image->parent[my_child_num].process_status != SB_WORKING)

   

int ap_graceful_stop_signalled(void)

{

    /* not ever called anymore... */
@@ -581,12 +573,11 @@ static void child_main(int child_num_arg) 
    apr_signal(SIGHUP, please_die_gracefully);



    ap_sync_scoreboard_image();

    while (!I_AM_TO_SHUTDOWN()) {

    while (!die_now) {



	/* Prepare to receive a SIGWINCH due to graceful restart so that

	 * we can exit cleanly.

	 */

	apr_signal(SIGWINCH, please_die_gracefully);

        apr_signal(SIGTERM, just_die);



	/*
@@ -669,13 +660,20 @@ static void child_main(int child_num_arg) 
	     */

	    for (;;) {

                ap_sync_scoreboard_image();

		if (I_AM_TO_SHUTDOWN()) {

		if (die_now) {

		    /* we didn't get a socket, and we were told to die */

		    clean_child_exit(0);

		}

		stat = apr_accept(&csd, sd, ptrans);

		if (stat == APR_SUCCESS || !APR_STATUS_IS_EINTR(stat))

		    break;

                /* In reality, this could be done later, but to keep it

                 * consistent with MPMs that have a thread race-condition,

                 * we will do it here.

                 */

                if (!ap_mpm_pod_check(pod)) {

                    die_now = 1;

                }

	    }



	    if (stat == APR_SUCCESS)
@@ -777,19 +775,13 @@ static void child_main(int child_num_arg) 
	    }



            ap_sync_scoreboard_image();

	    if (I_AM_TO_SHUTDOWN()) {

	    if (die_now) {

		clean_child_exit(0);

	    }

	}



	SAFE_ACCEPT(accept_mutex_off());	/* unlock after "accept" */



	/* We've got a socket, let's at least process one request off the

	 * socket before we accept a graceful restart request.  We set

	 * the signal to ignore because we don't want to disturb any

	 * third party code.

	 */

	apr_signal(SIGWINCH, SIG_IGN);

	/*

	 * We now have a connection, so set it up with the appropriate

	 * socket options, file descriptors, and read/write buffers.
@@ -894,7 +886,6 @@ static int make_child(server_rec *s, int slot) 
	 * requested there's no race condition here.

	 */

	apr_signal(SIGHUP, please_die_gracefully);

	apr_signal(SIGWINCH, please_die_gracefully);

	apr_signal(SIGTERM, just_die);

        ap_scoreboard_image->parent[slot].process_status = SB_WORKING;

	child_main(slot);
@@ -940,7 +931,7 @@ static int idle_spawn_rate = 1; 
#endif

static int hold_off_on_exponential_spawning;



static void perform_idle_server_maintenance(void)

static void perform_idle_server_maintenance(apr_pool_t *p)

{

    int i;

    int to_kill;
@@ -1002,7 +993,7 @@ static void perform_idle_server_maintenance(void) 
	 * shut down gracefully, in case it happened to pick up a request

	 * while we were counting

	 */

	kill(ap_scoreboard_image->parent[to_kill].pid, SIGWINCH);

	ap_mpm_pod_signal(pod);

	idle_spawn_rate = 1;

    }

    else if (idle_count < ap_daemons_min_free) {
@@ -1088,6 +1079,7 @@ int ap_mpm_run(apr_pool_t *_pconf, apr_pool_t *plog, server_rec *s) 
{

    int index;

    int remaining_children_to_start;

    apr_status_t rv;



    pconf = _pconf;
@@ -1099,6 +1091,11 @@ int ap_mpm_run(apr_pool_t *_pconf, apr_pool_t *plog, server_rec *s) 
	/* XXX: hey, what's the right way for the mpm to indicate a fatal error? */

	return 1;

    }

    if ((rv = ap_mpm_pod_open(pconf, &pod))) {

        ap_log_error(APLOG_MARK, APLOG_CRIT, rv, s,

		"Could not open pipe-of-death.");

        return 1;

    }



    SAFE_ACCEPT(accept_mutex_init(pconf));

    if (!is_graceful) {
@@ -1209,7 +1206,7 @@ int ap_mpm_run(apr_pool_t *_pconf, apr_pool_t *plog, server_rec *s) 
	    continue;

	}



	perform_idle_server_maintenance();

	perform_idle_server_maintenance(pconf);

#ifdef TPF

    shutdown_pending = os_check_server(tpf_server_name);

    ap_check_signals();
@@ -1244,7 +1241,6 @@ int ap_mpm_run(apr_pool_t *_pconf, apr_pool_t *plog, server_rec *s) 


    /* we've been told to restart */

    apr_signal(SIGHUP, SIG_IGN);

    apr_signal(SIGWINCH, SIG_IGN);

    if (one_process) {

	/* not worth thinking about */

	return 1;
@@ -1264,12 +1260,11 @@ int ap_mpm_run(apr_pool_t *_pconf, apr_pool_t *plog, server_rec *s) 


    if (is_graceful) {

	ap_log_error(APLOG_MARK, APLOG_NOERRNO|APLOG_NOTICE, 0, ap_server_conf,

		    "SIGWINCH received.  Doing graceful restart");

		    "Graceful restart requested, doing restart");



	/* kill off the idle ones */

	if (unixd_killpg(getpgrp(), SIGWINCH) < 0) {

	    ap_log_error(APLOG_MARK, APLOG_WARNING, errno, ap_server_conf, "killpg SIGWINCH");

	}

        ap_mpm_pod_killpg(pod, ap_daemons_limit);



#ifndef SCOREBOARD_FILE

	/* This is mostly for debugging... so that we know what is still

	    * gracefully dealing with existing request.  But we can't really

server/mpm_common.c

+84 −0
Original line number Diff line number Diff line
@@ -78,6 +78,7 @@ 
#include "mpm.h"

#include "mpm_common.h"

#include "ap_mpm.h"

#include "ap_listen.h"



#ifdef HAVE_PWD_H

#include <pwd.h>
@@ -338,4 +339,87 @@ int initgroups(const char *name, gid_t basegid) 
}

#endif /* def NEED_INITGROUPS */



#ifdef AP_MPM_USES_POD



AP_DECLARE(apr_status_t) ap_mpm_pod_open(apr_pool_t *p, ap_pod_t **pod)

{

    apr_status_t rv;



    *pod = apr_palloc(p, sizeof(**pod));

    rv = apr_file_pipe_create(&((*pod)->pod_in), &((*pod)->pod_out), p);

    apr_file_pipe_timeout_set((*pod)->pod_out, 0);

    (*pod)->p = p;

    return rv;

}



AP_DECLARE(apr_status_t) ap_mpm_pod_check(ap_pod_t *pod)

{

    char c;

    apr_size_t len = 1;

    apr_status_t rv;



    rv = apr_file_read(pod->pod_in, &c, &len);



    if ((rv == APR_SUCCESS) && (len == 1)) {

        return APR_SUCCESS;

    }

    if (rv != APR_SUCCESS) {

        return rv;

    }

    return AP_NORESTART;

}



AP_DECLARE(apr_status_t) ap_mpm_pod_close(ap_pod_t *pod)

{

    apr_status_t rv;



    rv = apr_file_close(pod->pod_out);

    if (rv != APR_SUCCESS) {

        return rv;

    }



    rv = apr_file_close(pod->pod_in);

    if (rv != APR_SUCCESS) {

        return rv;

    }

    return rv;

}



AP_DECLARE(apr_status_t) ap_mpm_pod_signal(ap_pod_t *pod)

{

    apr_socket_t *sock;

    apr_sockaddr_t *sa;

    apr_status_t rv;

    char char_of_death = '!';

    apr_size_t one = 1;



    do {

        if ((rv = apr_file_write(pod->pod_out, &char_of_death, &one))

                                 != APR_SUCCESS) {

            if (APR_STATUS_IS_EINTR(rv)) {

                continue;

            }

            else {

                ap_log_error(APLOG_MARK, APLOG_WARNING, rv, ap_server_conf,

                             "write pipe_of_death");

                return rv;

            }

        }

    } while (1);

    

    apr_sockaddr_info_get(&sa, "127.0.0.1", APR_UNSPEC, ap_listeners->bind_addr->port, 0, pod->p);

    apr_socket_create(&sock, sa->family, SOCK_STREAM, pod->p);

    apr_connect(sock, sa);    

    apr_socket_close(sock);



    return APR_SUCCESS;

}



AP_DECLARE(void) ap_mpm_pod_killpg(ap_pod_t *pod, int num)

{

    int i;

    for (i = 0; i < num; i++) {

        ap_mpm_pod_signal(pod);

    }

}

#endif