Plan 9 from Bell Labs 2009-07-18

sys/man/8/listen

@@ -3,7 +3,7 @@
 listen, listen1, tcp7, tcp9, tcp19, tcp21, tcp22, tcp23, tcp25, tcp53, tcp110, tcp113, tcp143, tcp513, tcp515, tcp564, tcp565, tcp566, tcp567, tcp993, tcp995, tcp1723, tcp17007, tcp17008, tcp17009, tcp17010, tcp17013 \- listen for calls on a network device
 .SH SYNOPSIS
 .B aux/listen
-.RB [ -q ]
+.RB [ -iq ]
 .RB [ -d
 .IR srvdir ]
 .RB [ -t
@@ -59,6 +59,9 @@ selects an alternate
 Option
 .B -q
 suppresses affirmative log information.
+Option
+.B -i
+suppresses the periodic scan of the service directories for changes.
 .PP
 Service names are made by concatenating the name of
 the network with the name of the service or port.

sys/src/cmd/aux/listen.c

@@ -34,6 +34,7 @@ void	listendir(char*, char*, int);
 char	listenlog[] = "listen";
 
 int	quiet;
+int	immutable;
 char	*cpu;
 char	*proto;
 Announce *announcements;
@@ -85,6 +86,7 @@ main(int argc, char *argv[])
 	trustdir = 0;
 	proto = "tcp";
 	quiet = 0;
+	immutable = 0;
 	argv0 = argv[0];
 	cpu = getenv("cputype");
 	if(cpu == 0)
@@ -103,6 +105,13 @@ main(int argc, char *argv[])
 	case 'n':
 		namespace = EARGF(usage());
 		break;
+	case 'i':
+		/*
+		 * fixed configuration, no periodic
+		 * rescan of the service directory.
+		 */
+		immutable = 1;
+		break;
 	default:
 		usage();
 	}ARGEND;
@@ -180,12 +189,12 @@ listendir(char *protodir, char *srvdir, int trusted)
 	notify(dingdong);
 
 	pid = getpid();
+	scandir(proto, protodir, srvdir);
 	for(;;){
 		/*
 		 * loop through announcements and process trusted services in
 		 * invoker's ns and untrusted in none's.
 		 */
-		scandir(proto, protodir, srvdir);
 		for(a = announcements; a; a = a->next){
 			if(a->announced > 0)
 				continue;
@@ -221,9 +230,20 @@ listendir(char *protodir, char *srvdir, int trusted)
 			}
 		}
 
-		/* pick up any children that gave up and sleep for at least 60 seconds */
+		/*
+		 * if not running a fixed configuration,
+		 * pick up any children that gave up and
+		 * sleep for at least 60 seconds.
+		 * If a service process dies in a fixed
+		 * configuration what should be done -
+		 * nothing? restart? restart after a delay?
+		 * - currently just wait for something to
+		 * die and delay at least 60 seconds
+		 * between restarts.
+		 */
 		start = time(0);
-		alarm(60*1000);
+		if(!immutable)
+			alarm(60*1000);
 		while((wm = wait()) != nil) {
 			for(a = announcements; a; a = a->next)
 				if(a->announced == wm->pid) {
@@ -234,8 +254,13 @@ listendir(char *protodir, char *srvdir, int trusted)
 						a->whined = 1;
 				}
 			free(wm);
+			if(immutable)
+				break;
+		}
+		if(!immutable){
+			alarm(0);
+			scandir(proto, protodir, srvdir);
 		}
-		alarm(0);
 		start = 60 - (time(0)-start);
 		if(start > 0)
 			sleep(start*1000);