#ifndef lint
static char rcsId[] = "$Id: restart.c,v 1.2 2000/03/15 14:00:21 claude Exp $";
#endif /* lint */

/*
 * restart
 *
 * Keeps alive fragiles daemons like xfs....
 *
 * Claude Scarpelli <claude@genoscope.cns.fr>, 18 janvier 1999
 *
 * $Log: restart.c,v $
 * Revision 1.2  2000/03/15  14:00:21  claude
 * improved english translation
 *
 * Revision 1.1  1999/01/18  15:50:22  claude
 * Initial revision
 *
 *
 *
 *
 * perldoc:
 *
=head1 NAME

B<restart> - controls and restart daemons.

=head1 SYNOPSIS

B<restart> [B<-fv>] [B<-n> nexec] [B<-t> time] command [arguments...]

=head1 FLAGS

B<-f> starts the daemon B<restart> in the foreground, ie it does not B<fork()>,

B<-v> verbose

B<-n> number of process that can be started in the time interval specified with  B<-t> (default 30),

B<-t> time interval (default 60 seconds). No more that B<nexec> process can be started in the time interval. If this condition occurs, B<restart> stops.



=head1 PARAMETERS

B<command> The name of a utility that is to be invoked.

B<argument> Any string to be supplied as an argument to the command.

=head1 DESCRIPTION

Some daemons, like B</usr/bin/X11/xfs>, crash very often. B<restart> can be used to automagically restart them, in a controlled fashion.

=head1 NOTES

B<restart> logs in B<syslog()>, B<facility> LOG_LOCAL5, B<priority> LOG_INFO.


=head1 AUTHOR

Claude Scarpelli, CNS-Genoscope, <claude@genoscope.cns.fr>

$Source: /usr/local/src/system/divers/RCS/restart.c,v $

$Id: restart.c,v 1.2 2000/03/15 14:00:21 claude Exp $

=cut

 */



#include <stdlib.h>
#include <stdio.h>
#include <syslog.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <libgen.h>
#include <unistd.h>
#include <signal.h>
#include <errno.h>

static char usage[] = 
"%s: uage: %s [-fv] [-t time] [-n nb_exec] command [argument...]\n";



static int nexec = 30;		/* no more that nexec exec().... */
static unsigned int tslot = 60;	/* ....each 60 seconds */
static int verbose = 0;
static int foregroundmode = 0;	/* default: daemon mode */

static unsigned int n = 0;	/* number of exec in this time slot */
static int inprogress = 0;	/* != 0 if alarm() in progress */




static void
die_with_usage(char *progname){
  char *p = basename(progname);

  fprintf(stderr, usage, p, p);
  exit(1);
}



static void
daemonize(){
  pid_t pid = fork();
  pid_t pgid;

  switch(pid){
  case -1:
    perror("fork");
    syslog(LOG_INFO, "fork failed: %m");
    exit(1);
    break;
  case 0:
    if (verbose)
      syslog(LOG_INFO, "daemon running, pid = %d", getpid());

    pgid = setpgrp();
    if (verbose)
      syslog(LOG_INFO, "Process group ID is %d", pgid);

    return;
    break;
  default:
    if (verbose)
      syslog(LOG_INFO, "child started, with pid = %d", pid);
    exit(0);
    break;
  }
}
	     


static pid_t
spawn(char **argv){
  pid_t pid;


  switch (pid = fork()){
  case -1:
    if (foregroundmode)
      perror ("fork");

    syslog(LOG_INFO, "fork failed: %m");
    exit(1);
    break;
  case 0:
    execvp(argv[0], argv);
    if (foregroundmode)
      perror(argv[0]);

    syslog(LOG_INFO, "%s: %m", argv[0]);

    _exit(1);
    break;
  }
  
  return pid;
}  


static void
doc(int signum){
  return;
}

static void
bip(int signum){
  inprogress = 0;
  return;
}


int
main(int argc, char **argv){
  int c;
  int error = 0;
  struct sigaction s;

  openlog(basename(argv[0]), LOG_PID, LOG_LOCAL5);


  while((c = getopt(argc, argv, "fvt:n:")) != EOF)
    switch (c){
    case 'f':
      foregroundmode++;
      break;
    case 't':
      tslot = atoi(optarg);
      break;
    case 'n':
      nexec = atoi(optarg);
      break;
    case 'v':
      verbose++;
      break;
    default:
      error++;
      break;
    }

  if ((tslot <= 0) || (nexec <= 0)){
    fprintf(stderr, "-t and -n args (%d %d) must be > 0\n",
	    tslot,
	    nexec);
    syslog(LOG_INFO, "-t and -n args (%d %d) must be > 0\n",
	   tslot,
	   nexec);

    error++;
  }

  if ((argc - optind) < 1)
    error++;

  if (error)
    die_with_usage(argv[0]);


  if (!foregroundmode)
    daemonize();

  if (verbose){
    if (foregroundmode)
      fprintf(stderr, 
"launching and controlling %s, but not more than %d times per %d seconds\n",
	      argv[optind],
	      nexec,
	      tslot);

    syslog(LOG_INFO,
"launching and controlling %s, but not more than %d times per %d seconds\n",
	   argv[optind],
	   nexec,
	   tslot);
  }


  s.sa_sigaction = doc;
  s.sa_mask = 0;
  s.sa_flags = SA_RESTART;

  sigaction(SIGCHLD, &s, NULL);

  s.sa_sigaction = bip;
  s.sa_mask = 0;
  s.sa_flags = SA_RESTART;

  sigaction(SIGALRM, &s, NULL);



  argv += optind;

  for(;;){
    pid_t pid, wpid;
    int wstatus;

    if (!inprogress){
      inprogress++;
      n = 0;

      alarm(tslot);
    }

    n++;

    if (n >= nexec){
      if (foregroundmode)
	fprintf(stderr, "%d exec() in this time slot, exiting\n", n);

      syslog(LOG_INFO, "%d exec() in this time slot, exiting\n", n);

      exit(1);
    }

    if (verbose){
      if (foregroundmode)
	fprintf(stderr, "starting %s, %dth in this time slot\n", 
		argv[0], n);

      syslog(LOG_INFO, "starting %s, %dth in this time slot\n", 
	     argv[0], n);
    }


    if ((pid = spawn(argv)) <= 0){
      if (foregroundmode)
	fprintf(stderr, "spawn failed, exiting\n");

      syslog(LOG_INFO, "spawn failed, exiting\n");

      exit(1);
    }

    
    if (verbose){
      if (foregroundmode)
	fprintf(stderr, "child process %d started\n", pid);

      syslog(LOG_INFO, "child process %d started\n", pid);
    }

    for (;;){
      wpid = wait(&wstatus);

      if (verbose){
	if (foregroundmode)
	  fprintf(stderr, "wait: pid = %d, status = 0x%08x\n",
		  wpid, wstatus);

	syslog(LOG_INFO, "wait: pid = %d, status = 0x%08x\n",
	       wpid, wstatus);
      }

      
      if (wpid != pid){
	if (foregroundmode)
	  fprintf(stderr, 
		  "spurious wait (pid = %d, status 0x%08x, errno = %d)\n", 
		  wpid, wstatus, errno);

	syslog(LOG_INFO, "spurious wait (pid = %d, status 0x%08x, %m)\n", 
	       wpid, wstatus);

	continue;
      }

    
      if (wstatus){
	if (WIFSTOPPED(wstatus) || WIFCONTINUED(wstatus))
	  continue;

	if (WIFSIGNALED(wstatus)){
	  if (foregroundmode)
	    fprintf(stderr, "child process terminated by signal %d\n",
		    WTERMSIG(wstatus));

	  syslog(LOG_INFO, "child process terminated by signal %d\n",
		    WTERMSIG(wstatus));

	  break;
	}

	if (foregroundmode)
	  fprintf(stderr, "child process terminated with return code %d\n",
		  WEXITSTATUS(wstatus));

	syslog(LOG_INFO, "child process terminated with return code %d\n",
	       WEXITSTATUS(wstatus));

	break;

      }
      if (foregroundmode)
	fprintf(stderr, "child process terminated with return code %d\n",
		WEXITSTATUS(wstatus));

      syslog(LOG_INFO, "child process terminated with return code %d\n",
	     WEXITSTATUS(wstatus));

      break;
    }

  }
}