svc.c: added -w option to wait for service to be up

daemontools-x/doc/ChangeLog

@@ -8,6 +8,8 @@
 04. svps: use .svscan.pid from service directory of each svscan instance
 - 10/10/2024
 05. runpod.sh: set systemd only if not set
+- 20/10/2024
+06. svc.c: added -w option to wait for service to be up
 
 * Tue Aug 06 2024 12:48:42 +0000 Manvendra Bhangui <[email protected]> 1.1.5-1.1%{?dist}
 Release 1.1.5-1.1 Start 05/02/2024 End 06/08/2024

daemontools-x/supervise.8

@@ -106,9 +106,9 @@ another service is implemented by opening \fIs\fR/\fIsupervise\fR/\fIup\fR
 in write mode.
 
 \fIsupervise\fR(8) opens \fIs\fR/\fIsupervise\fR/\fIup\fR in write mode
-just before it executes ./run. Hence, if service \fIw\fR is up, write on
+just after it executes ./run. Hence, if service \fIw\fR is up, write on
 \fIw\fR/\fIsupervise\fR/\fIup\fR, returns immediately. If service \fIw\fR
-is down, the write will block till \fIw\fR is up and running. If servicee
+is down, the write will block untill \fIw\fR is up and running. If service
 \fIw\fR doesn't have \fBsupervise\fR running, \fPsupervise\fR will wait for
 60 seconds before opening the file \fIw\fR/\fIsupervise\fR/\fIup\fR again
 in write mode. The default value of 60 seconds gets overriden by the
@@ -128,8 +128,8 @@ returns, it means \fBsupervise\fR(8) is running.
 .IP \[bu] 2
 \fIs\fR/\fIsupervise\fR/\fIup\fR - clients can open this in write mode
 (O_WRONLY) to test if service \fIs\fR is up. Any client that opens this
-fifo will block until the service \fIs\fR is up. If write returns, it means
-service \fIs\fR is running.
+fifo in O_WRONLY mode, will block until the service \fIs\fR is up. If write
+returns, it means service \fIs\fR has executed \fIs\fR/\fIrun\fR.
 .PP
 \fBsupervise\fR logs informational, warning and error messages to
 descriptor 2. Informational messages can be turned on by setting the

daemontools-x/svc.8

@@ -1,25 +1,19 @@
+.\" vim: tw=75
 .TH svc 8
 .SH NAME
 svc \- controls services monitored by
 .BR supervise(8).
 .SH SYNOPSIS
-.B svc
-[
-.B \-udopchaitkx
-]
-.I services
+\fBsvc\fR [ \fB\-udopchaitkx\fR ] \fIservices\fR
+
 .SH DESCRIPTION
-.I services
-consists of any number of arguments, each argument naming a directory used by
-.BR supervise (8).
+\fIservices\fR consists of any number of arguments, each argument naming a
+directory used by \fBsupervise\fR(8).
 
-.B svc
-applies all the options to each
-.I service
-in turn.
+\fBsvc\fR applies all the options to each \fIservice\fR in turn.
 
 .SH OPTIONS
-.TP
+.TP 4
 .B \-u
 Up. If the
 .I service
@@ -112,6 +106,16 @@ a KILL signal.
 For all options above, the signal will be sent to the entire process group instead of just the pid of
 the \fIservice\fR.
 
+.TP
+.B \-w
+Wait. \fBsvc\fR(8) will wait for \fIservice\fR to be up.
+\fBsupervise\fR(8) opens the named pipe \fIservice\fR/\fIup\fR after
+executing \fIservice\fR/\fIrun\fR. \fBsvc\fR opens this named pipe in
+O_WRONLY mode in blocking mode, thus making \fBsvc\fR wait till the named
+pipe is opened by \fBsupervise\fR. This option can be used by any program
+to wait for a supervised service. This can also be used by \fBsupervise\fR
+to setup inter-dependencies between services.
+
 .TP
 .B \-x
 Exit.

daemontools-x/svc.c

@@ -1,40 +1,8 @@
 /*
- * $Log: svc.c,v $
- * Revision 1.11  2024-05-09 22:39:36+05:30  mbhangui
- * fix discarded-qualifier compiler warnings
- *
- * Revision 1.10  2023-03-04 14:42:52+05:30  Cprogrammer
- * check for supervise/ok in original service dir before run filesystem
- *
- * Revision 1.9  2020-11-30 23:19:48+05:30  Cprogrammer
- * change warning text message for missing directory in /run
- *
- * Revision 1.8  2020-11-30 22:53:40+05:30  Cprogrammer
- * continue instead of exit on run_init() failure
- *
- * Revision 1.7  2020-10-08 18:34:02+05:30  Cprogrammer
- * use /run, /var/run if system supports it
- *
- * Revision 1.6  2020-08-29 08:41:22+05:30  Cprogrammer
- * new option 'G' to send signal to entire process group
- *
- * Revision 1.5  2020-06-10 17:37:42+05:30  Cprogrammer
- * new option restart (stop and restart) a service
- *
- * Revision 1.4  2008-06-07 19:11:45+05:30  Cprogrammer
- * added sigquit, sigusr1, sigusr2 signals
- *
- * Revision 1.3  2004-10-22 20:31:16+05:30  Cprogrammer
- * added RCS id
- *
- * Revision 1.2  2004-10-12 00:09:01+05:30  Cprogrammer
- * replaced buffer functions with substdio
- *
- * Revision 1.1  2003-12-31 18:37:19+05:30  Cprogrammer
- * Initial revision
- *
+ * $Id: $
  */
 #include <unistd.h>
+#include <fcntl.h>
 #include "ndelay.h"
 #include "strerr.h"
 #include "error.h"
@@ -61,22 +29,24 @@ int             fdorigdir;
 int
 main(int argc, char **argv)
 {
-	int             opt, i;
+	int             opt, sopt = 0, i;
 	int             fd, exit_stat;
 	char           *dir;
 
 	sig_ignore(sig_pipe);
-	while ((opt = getopt(argc, argv, "udropchUaitkxq12G")) != opteof) {
+	while ((opt = getopt(argc, argv, "udropchUaitkxq12Gw")) != opteof) {
 		if (opt == '?')
 			strerr_die1x(100,
 				 "svc options: u up, d down, r restart, o once, x exit, p pause, c continue h hup\n"
 				 "             a alarm, i interrupt, t term, k kill, q quit, U|1 SIGUSR1, 2 SIGUSR2\n"
 				 "             G process group");
 		else
 		if (datalen < sizeof data) {
-			if (byte_chr(data, datalen, opt) == datalen)
+			if (opt != 'w' && byte_chr(data, datalen, opt) == datalen)
 				data[datalen++] = opt;
 		}
+		if (opt == 'w')
+			sopt = opt;
 	}
 	argv += optind;
 	if ((fdorigdir = open_read(".")) == -1)
@@ -125,19 +95,40 @@ main(int argc, char **argv)
 			}
 		}
 #endif
-		if (fd == -1 && (fd = open_write("supervise/control")) == -1) {
+		if (datalen && fd == -1 && (fd = open_write("supervise/control")) == -1) {
 			if (errno == error_nodevice || errno == error_noent) {
 				strerr_warn4(WARN, "unable to control ", dir, ": supervise not running: ", 0);
 				exit_stat = 2;
-			} else
+			} else {
+				exit_stat = 1;
 				strerr_warn4(WARN, "unable to control ", dir, ": ", &strerr_sys);
-		} else {
+			}
+		} else
+		if (datalen) {
 			ndelay_off(fd);
 			substdio_fdbuf(&b, write, fd, bspace, sizeof bspace);
 			if (substdio_putflush(&b, data, datalen) == -1)
 				strerr_warn4(WARN, "error writing commands to ", dir, ": ", &strerr_sys);
 			close(fd);
 		}
+		if (sopt == 'w') {
+			if (datalen)
+				sleep(1);
+			while (1) {
+				if ((fd = open("supervise/up", O_WRONLY, 0)) == -1) { /* this should block if service is down */
+					if (errno == error_nodevice || errno == error_noent) {
+						sleep(1);
+						continue;
+					} else {
+						strerr_warn4(WARN, "unable to wait for ", dir, ": ", &strerr_sys);
+						break;
+					}
+				} else { /*- service is up */
+					close(fd);
+					break;
+				}
+			}
+		}
 		if (fchdir(fdorigdir) == -1)
 			strerr_die2sys(111, FATAL, "unable to revert directory: ");
 	} /* while ((dir = *argv++)) */
@@ -151,3 +142,40 @@ getversion_svc_c()
 
 	x++;
 }
+
+/*
+ * $Log: svc.c,v $
+ * Revision 1.11  2024-05-09 22:39:36+05:30  mbhangui
+ * fix discarded-qualifier compiler warnings
+ *
+ * Revision 1.10  2023-03-04 14:42:52+05:30  Cprogrammer
+ * check for supervise/ok in original service dir before run filesystem
+ *
+ * Revision 1.9  2020-11-30 23:19:48+05:30  Cprogrammer
+ * change warning text message for missing directory in /run
+ *
+ * Revision 1.8  2020-11-30 22:53:40+05:30  Cprogrammer
+ * continue instead of exit on run_init() failure
+ *
+ * Revision 1.7  2020-10-08 18:34:02+05:30  Cprogrammer
+ * use /run, /var/run if system supports it
+ *
+ * Revision 1.6  2020-08-29 08:41:22+05:30  Cprogrammer
+ * new option 'G' to send signal to entire process group
+ *
+ * Revision 1.5  2020-06-10 17:37:42+05:30  Cprogrammer
+ * new option restart (stop and restart) a service
+ *
+ * Revision 1.4  2008-06-07 19:11:45+05:30  Cprogrammer
+ * added sigquit, sigusr1, sigusr2 signals
+ *
+ * Revision 1.3  2004-10-22 20:31:16+05:30  Cprogrammer
+ * added RCS id
+ *
+ * Revision 1.2  2004-10-12 00:09:01+05:30  Cprogrammer
+ * replaced buffer functions with substdio
+ *
+ * Revision 1.1  2003-12-31 18:37:19+05:30  Cprogrammer
+ * Initial revision
+ *
+ */