add daemon supervisor

The supervise-daemon process is meant to be a lightweight supervisor
which can monitor and restart a daemon if it crashes.

sh/Makefile

@@ -1,7 +1,8 @@
 DIR=	${LIBEXECDIR}/sh
 SRCS=	init.sh.in functions.sh.in gendepends.sh.in \
 	openrc-run.sh.in rc-functions.sh.in tmpfiles.sh.in ${SRCS-${OS}}
-INC=	rc-mount.sh functions.sh rc-functions.sh s6.sh start-stop-daemon.sh
+INC=	functions.sh rc-mount.sh rc-functions.sh s6.sh start-stop-daemon.sh \
+		supervise-daemon.sh
 BIN=	gendepends.sh init.sh openrc-run.sh tmpfiles.sh ${BIN-${OS}}
 
 INSTALLAFTER=	_installafter

sh/openrc-run.sh.in

@@ -154,6 +154,7 @@ start()
 	local func=ssd_start
 	case "$supervisor" in
 		s6) func=s6_start ;;
+		supervise-daemon) func=supervise_start ;;
 		?*)
 			ewarn "Invalid supervisor, \"$supervisor\", using start-stop-daemon"
 			;;
@@ -166,6 +167,7 @@ stop()
 	local func=ssd_stop
 	case "$supervisor" in
 		s6) func=s6_stop ;;
+		supervise-daemon) func=supervise_stop ;;
 		?*)
 			ewarn "Invalid supervisor, \"$supervisor\", using start-stop-daemon"
 			;;
@@ -178,6 +180,7 @@ status()
 	local func=ssd_status
 	case "$supervisor" in
 		s6) func=s6_status ;;
+		supervise-daemon) func=supervise_status ;;
 		?*)
 			ewarn "Invalid supervisor, \"$supervisor\", using start-stop-daemon"
 			;;
@@ -215,6 +218,7 @@ fi
 # load service supervisor functions
 sourcex "@LIBEXECDIR@/sh/s6.sh"
 sourcex "@LIBEXECDIR@/sh/start-stop-daemon.sh"
+sourcex "@LIBEXECDIR@/sh/supervise-daemon.sh"
 
 # Set verbose mode
 if yesno "${rc_verbose:-$RC_VERBOSE}"; then

sh/supervise-daemon.sh

@@ -0,0 +1,49 @@
+# start / stop / status functions for supervise-daemon
+
+# Copyright (c) 2016 The OpenRC Authors.
+# See the Authors file at the top-level directory of this distribution and
+# https://github.com/OpenRC/openrc/blob/master/AUTHORS
+#
+# This file is part of OpenRC. It is subject to the license terms in
+# the LICENSE file found in the top-level directory of this
+# distribution and at https://github.com/OpenRC/openrc/blob/master/LICENSE
+# This file may not be copied, modified, propagated, or distributed
+#    except according to the terms contained in the LICENSE file.
+
+supervise_start()
+{
+	if [ -z "$command" ]; then
+		ewarn "The command variable is undefined."
+		ewarn "There is nothing for ${name:-$RC_SVCNAME} to start."
+		return 1
+	fi
+
+	ebegin "Starting ${name:-$RC_SVCNAME}"
+	eval supervise-daemon --start \
+		${pidfile:+--pidfile} $pidfile \
+		${command_user+--user} $command_user \
+		$supervise_daemon_args \
+		$command \
+		-- $command_args $command_args_foreground
+	rc=$?
+	[ -n "${pidfile}" ] && service_set_value "pidfile" "${pidfile}"
+	eend $rc "failed to start $RC_SVCNAME"
+}
+
+supervise_stop()
+{
+	local startpidfile="$(service_get_value "pidfile")"
+	pidfile="${startpidfile:-$pidfile}"
+	[ -n "$pidfile" ] || return 0
+	ebegin "Stopping ${name:-$RC_SVCNAME}"
+	supervise-daemon --stop \
+		${pidfile:+--pidfile} $pidfile \
+		${stopsig:+--signal} $stopsig
+
+	eend $? "Failed to stop $RC_SVCNAME"
+}
+
+supervise_status()
+{
+	_status
+}