make use of lock file

Signed-off-by: Andy Green <andy.green@linaro.org>

README-test-server

@@ -177,6 +177,29 @@ Incrementing numbers should appear in the browser display.
 
 By default the test server logs to both stderr and syslog.
 
+
+Running test server as a Daemon
+-------------------------------
+
+You can use the -D option on the test server to have it fork into the
+background and return immediately.  In this daemonized mode all stderr is
+disabled and logging goes only to syslog, eg, /var/log/messages or similar.
+
+The server maintains a lockfile at /tmp/.lwsts-lock that contains the pid
+of the master process, and deletes this file when the master process
+terminates.
+
+To stop the daemon, do
+
+  kill `cat /tmp/.lwsts-lock`
+
+If it finds a stale lock (the pid mentioned in the file does not exist
+any more) it will delete the lock and create a new one during startup.
+
+If the lock is valid, the daemon will exit with a note on stderr that
+it was already running.s
+
+
 Using SSL on the server side
 ----------------------------
 

lib/daemonize.c

@@ -21,7 +21,7 @@
 #include <unistd.h>
 #include <errno.h>
 
-static int pid_daemon;
+int pid_daemon;
 static char lock_path[PATH_MAX];
 
 static void
@@ -64,6 +64,14 @@ child_handler(int signum)
 	}
 }
 
+static void lws_daemon_closing(int sigact)
+{
+	if (getpid() == pid_daemon)
+		unlink(lock_path);
+
+	kill(getpid(), SIGKILL);
+}
+
 /*
  * You just need to call this from your main(), when it
  * returns you are all set "in the background" decoupled
@@ -76,11 +84,31 @@ int
 lws_daemonize(const char *_lock_path)
 {
 	pid_t sid, parent;
+	int fd;
+	char buf[10];
+	int n, ret;
+	struct sigaction act;
 
 	/* already a daemon */
 	if (getppid() == 1)
 		return (1);
 
+	fd = open(_lock_path, O_RDONLY);
+	if (fd > 0) {
+		n = read(fd, buf, sizeof buf);
+		close(fd);
+		if (n) {
+			n = atoi(buf);
+			ret = kill(n, 0);
+			if (ret >= 0) {
+				fprintf(stderr, "Daemon already running from pid %d, aborting\n", n);
+				exit(1);
+			}
+			fprintf(stderr, "Removing stale lock file %s from dead pid %d\n", _lock_path, n);
+			unlink(lock_path);
+		}
+	}
+
 	strncpy(lock_path, _lock_path, sizeof lock_path);
 	lock_path[sizeof(lock_path) - 1] = '\0';
 
@@ -114,6 +142,7 @@ lws_daemonize(const char *_lock_path)
 
 	/* At this point we are executing as the child process */
 	parent = getppid();
+	pid_daemon = getpid();
 
 	/* Cancel certain signals */
 	signal(SIGCHLD, SIG_DFL); /* A child process dies */
@@ -161,6 +190,13 @@ lws_daemonize(const char *_lock_path)
 	/* Tell the parent process that we are A-okay */
 	kill(parent, SIGUSR1);
 
+	act.sa_handler = lws_daemon_closing;
+	sigemptyset(&act.sa_mask);
+	act.sa_flags = 0;
+	act.sa_restorer = NULL;
+	
+	sigaction(SIGTERM, &act, NULL);
+
 	/* return to continue what is now "the daemon" */
 
 	return (0);

lib/libwebsockets.c

@@ -703,6 +703,10 @@ libwebsocket_service_fd(struct libwebsocket_context *context,
 	if (context->last_timeout_check_s != tv.tv_sec) {
 		context->last_timeout_check_s = tv.tv_sec;
 
+		/* if our parent went down, don't linger around */
+		if (context->started_with_parent && kill(context->started_with_parent, 0) < 0)
+			kill(getpid(), SIGTERM);
+
 		/* global timeout check once per second */
 
 		for (n = 0; n < context->fds_count; n++) {
@@ -1443,12 +1447,17 @@ libwebsocket_create_context(int port, const char *interf,
 	}
 #endif
 
-
 	context = (struct libwebsocket_context *) malloc(sizeof(struct libwebsocket_context));
 	if (!context) {
 		lwsl_err("No memory for websocket context\n");
 		return NULL;
 	}
+#ifndef NO_DAEMONIZE
+	extern int pid_daemon;
+	context->started_with_parent = pid_daemon;
+	lwsl_notice(" Started with daemon pid %d\n", pid_daemon);
+#endif
+
 	context->protocols = protocols;
 	context->listen_port = port;
 	context->http_proxy_port = 0;
@@ -1975,10 +1984,14 @@ libwebsockets_fork_service_loop(struct libwebsocket_context *context)
  * solaris, could remember ppid right after fork and wait for it to change.
  */
 
-        if (getppid() == 1)
-            break;
+		/* if our parent went down, don't linger around */
+		if (context->started_with_parent && kill(context->started_with_parent, 0) < 0)
+			kill(getpid(), SIGTERM);
+
+	        if (getppid() == 1)
+	            break;
 //#endif
-    }
+	}
 
 
 	return 1;

lib/private-libwebsockets.h

@@ -257,6 +257,8 @@ struct libwebsocket_context {
 	unsigned int options;
 	unsigned long last_timeout_check_s;
 
+	int started_with_parent;
+
 	int fd_random;
 	int listen_service_modulo;
 	int listen_service_count;

test-server/test-server.c

@@ -43,7 +43,6 @@ int count_pollfds;
 
 #endif /* EXTERNAL_POLL */
 
-//#define LWS_NO_FORK
 
 /*
  * This demo server shows how to use libwebsockets for one or more
@@ -562,6 +561,7 @@ int main(int argc, char **argv)
 		}
 	}
 
+#ifndef NO_DAEMONIZE
 	/* 
 	 * normally lock path would be /var/lock/lwsts or similar, to
 	 * simplify getting started without having to take care about
@@ -571,7 +571,7 @@ int main(int argc, char **argv)
 		fprintf(stderr, "Failed to daemonize\n");
 		return 1;
 	}
-
+#endif
 	/* we will only try to log things according to our debug_level */
 	setlogmask(LOG_UPTO (LOG_DEBUG));
 	openlog("lwsts", syslog_options, LOG_DAEMON);
@@ -685,6 +685,8 @@ int main(int argc, char **argv)
 		lwsl_err("Unable to fork service loop %d\n", n);
 		return 1;
 	}
+	if (n)
+		exit(0);
 
 	while (1) {