From Ape Wiki

[edit] APE Server watchdog

Set the SBIN_DIR define to the location of the bin folder for your APE server and compile it with

gcc watchdog.c -o aped_watchdog

Then launch your APE Server with

./aped_watchdog

The file ape.conf has to be in the same directory, If it's not the case specify the path to ape.conf with --cfg arguments.

./aped_watchdog --cfg /path/to/ape.conf

#include <sys/wait.h>
 
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <time.h>
#include <signal.h>
 
#define SBIN_DIR "/home/para/APE_rev/dir_2/APE_Server/bin"
#define BINPATH SBIN_DIR"/aped"
 
 
static volatile sig_atomic_t start_process    = 1;
 
static volatile pid_t pid = -1;
 
#define UNUSED(x) ( (void)(x) )
 
static void sigaction_handler(int sig, siginfo_t *si, void *context) {
	int exitcode;
 
	UNUSED(context);
	switch (sig) {
	case SIGINT: 
	case SIGTERM:
		/** forward the sig to the child */
		kill(pid, sig);
		break;
	case SIGHUP: /** do a graceful restart */
		/** do a graceful shutdown on the main process and start a new child */
		kill(pid, SIGINT);
 
		usleep(5 * 1000); /** wait 5 microsec */
 
		start_process = 1;
		break;
	case SIGCHLD:
		/** a child died, de-combie it */
		wait(&exitcode);
		break;
	}
}
 
int main(int argc, char **argv) {
	int is_shutdown = 0;
	struct sigaction act;
 
	UNUSED(argc);
 
	/**
	 * we are running as root BEWARE
	 */
 
	memset(&act, 0, sizeof(act));
	act.sa_handler = SIG_IGN;
	sigaction(SIGPIPE, &act, NULL);
	sigaction(SIGUSR1, &act, NULL);
 
	act.sa_sigaction = sigaction_handler;
	sigemptyset(&act.sa_mask);
	act.sa_flags = SA_SIGINFO;
 
	sigaction(SIGINT,  &act, NULL);
	sigaction(SIGTERM, &act, NULL);
	sigaction(SIGHUP,  &act, NULL);
	sigaction(SIGALRM, &act, NULL);
	sigaction(SIGCHLD, &act, NULL);
 
	/* check that the compiled in path has the right user,
	 *
	 * BEWARE: there is a race between the check here and the exec later
	 */
 
	while (!is_shutdown) {
		int exitcode = 0;
 
		if (start_process) {
			pid = fork();
 
			if (0 == pid) {
				/* i'm the child */
 
				argv[0] = BINPATH;
 
				execvp(BINPATH, argv);
 
				exit(1);
			} else if (-1 == pid) {
				/** error */
 
				return -1;
			}
 
			/* I'm the angel */
			start_process = 0;
		}
 
		if ((pid_t)-1 == waitpid(pid, &exitcode, 0)) {
			switch (errno) {
			case EINTR:
				/* someone sent a signal ... 
				 * do we have to shutdown or restart the process */
				break;
			case ECHILD:
				/** 
				 * make sure we are not in a race between the signal handler
				 * and the process restart */
				if (!start_process) is_shutdown = 1;
				break;
			default:
				break;
			}
		} else {
			/** process went away */
 
			if (WIFEXITED(exitcode)) {
				/** normal exit */
 
				is_shutdown = 1;
 
				fprintf(stderr, "%s.%d: child (pid=%d) exited normally with exitcode: %d\n", 
						__FILE__, __LINE__,
						pid,
						WEXITSTATUS(exitcode));
 
			} else if (WIFSIGNALED(exitcode)) {
				/** got a signal */
 
				fprintf(stderr, "%s.%d: child (pid=%d) exited unexpectedly with signal %d, restarting\n", 
						__FILE__, __LINE__,
						pid,
						WTERMSIG(exitcode));
 
				start_process = 1;
			}
		}
	}
 
	return 0;
}

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