/* This programm is written by G. Caronni in '97 <gec@acm.org> */

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <signal.h>
#include <string.h>


#define VERSION "1.1"
#define STOP_LOAD 1.6
#define RUN_LOAD 0.6
#define INTERVALL 60 /* seconds */
#define UPTIME          "/usr/ucb/uptime"

char *subprog[] = { "/home/caronni/desclient", "desclient", 
		    "-s", "keymaster.des.sollentuna.se", 
		    "-e", "gec@acm.org", "-n", "20", NULL};


int pid=0;
int verbose=0;

float getload(void)
{
  char buf[1024], *t;
  float load;
  FILE *p=popen(UPTIME,"r");
  
  if (!p) {
    perror("popen");
    if (verbose) printf("Collecting load stats failed.\n");
    if (verbose) printf("Terminating child...\n");
    kill (pid,SIGTERM);
    exit(2);
  }
  fgets(buf,sizeof(buf),p);
  pclose(p);
  t=strstr(buf,"load average");
  if (t) t=strtok(t,",");
  if (t) t=strtok(NULL,", ");
  if (t && sscanf(t,"%f",&load)==1) {
    if (verbose) printf("Scanned load: %0.2f\n",load);
  } else {
    if (verbose) printf("Parsing load stats failed.\n");
    if (verbose) printf("Terminating child...\n");
    kill (pid,SIGTERM);
    exit(2);
  }
  return load;
}


int main(int argc, char *argv[], char *envp[])
{
  
  extern int optind;
  extern char *optarg;
  int c;
  int errflg = 0;
  float stop_load, run_load;
  char **sprog=subprog;
  
  *envp=NULL;
  
  stop_load=run_load=0.0;
  
  while ((c = getopt(argc, argv, "vs:r:")) != EOF) {
    switch (c) {
    case 'v':
      verbose++;
      break;
    case 's':
      if (sscanf(optarg,"%f",&stop_load)!=1) errflg++;
      break;
    case 'r':
      if (sscanf(optarg,"%f",&run_load)!=1) errflg++;
      break;
    case '?':
      errflg++;
    }
  }
  if (!stop_load) {
    stop_load=STOP_LOAD;
    if (!run_load) run_load=RUN_LOAD;
  } else if (!run_load) run_load=stop_load;
  
  if (stop_load <= 1.0) errflg++;
  if (run_load > stop_load) errflg++;
  if (errflg) {
    (void)fprintf(stderr, 
		  "Usage: %s [-v] [-s stopload] [-r runload] [command to call]\n"
		  "       -v          verbose\n"
		  "       -s stopload process will be stopped if load surpassed\n"
		  "                   load specified must be higer than 1.0\n"
		  "       -r runload  process will be restarted at this load\n"
		  "                   load specified must be lower than stopload\n"
		  ,argv[0]);     
    exit(1);
  }
  if (optind < argc) sprog = &(argv[optind]); 
  
  if (verbose) {
    int i=0;
    printf("Load watcher (%s), runload: %0.2f, stopload: %0.2f, "
	   "command to be executed:\n",
	   VERSION, run_load,stop_load);
    while(sprog[i]) printf("%s ",sprog[i++]);
    printf("\n");
  }
  signal(SIGCHLD,SIG_IGN);
  
  /* ============================================ */
  if (!(pid=fork())) {
    execv(*sprog,sprog);
    perror("execv");
    exit(-1);
  }
  /* ============================================ */
  
  if (pid<0) {
    perror("fork");
    exit(-1);
  }
  sleep(1);
  
  while (1) {
    if (kill(pid,0)) {
      if (verbose) {
	perror("kill(pid,0)");
	fprintf(stderr, "Child process unreachable. Terminating...\n");
      }
      break;
    } 
    
    if (getload()>stop_load) {
      if (verbose) printf("Maximum load exceeded. Idling...\n");
      if (kill(pid,SIGSTOP)) {
	if (verbose) {
	  perror("kill(pid,SIGSTOP)");
	  fprintf(stderr,
		  "Child process unreachable. Terminating...\n");
	}
	break;
      }
      while(getload()>run_load) sleep (INTERVALL);
      if (verbose) printf("Load below threshold. Continuing...\n");
      if (kill(pid,SIGCONT)) {
	if (verbose) {
	  perror("kill(pid,SIGCONT)");
	  fprintf(stderr,
		  "Child process unreachable. Terminating...\n");
	}
	break;
      }
    }
    sleep(INTERVALL);
  }
  return 0;
}

/* EOT */