Create freebsd-rc-service.sh

This script exports FreeBSD rc service status information whether a
given service is running or not.

Sponsored by:  Klara Inc.
Sponsored by:  ELW – Entsorgungsbetriebe der Landeshauptstadt Wiesbaden
Signed-off-by: Mateusz Piotrowski <[email protected]>

freebsd-rc-service.sh

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+#! /bin/sh -
+#
+# Expose metrics about the status of FreeBSD rc(8) services.
+#
+# SYNOPSIS
+#	freebsd-rc-service.sh [-i ignored]
+#	freebsd-rc-service.sh -h
+#
+# DESCIPTION
+# This script should probably run as UID 0 in order to be able to successfully
+# get the status of each service (e.g., as of FreBSD 14.0-CURRENT, the cron's
+# PID file is readable only to UID 0).
+#
+# A status metric is provided for a service if:
+# - The service is enabled.
+# - The service provides a status command.
+# - The service is not ignored via the -i flag.
+#
+# This script accepts the following flags:
+# -h		Print help and exit.
+# -i ignored	Ignore specified services. Services have to be listed
+#		by their absolute paths,
+#		e.g., "/etc/rc.d/sendmail /etc/rc.d/ip6addrctl".
+#
+# METRICS
+# This script provides the following metrics:
+#
+# - freebsd_rc_service_status{path="PATH"} STATUS
+#   where:
+#   - PATH is an absolute path to the service script
+#   - STATUS is the exit code of the "quietstatus" command of the script.
+#
+# --
+#
+# Copyright 2022 Mateusz Piotrowski <[email protected]>
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# Author: Mateusz Piotrowski <[email protected]>
+
+#
+# Functions
+#
+
+help() {
+
+	cat 1>&2 <<EOF
+Usage: $0 [-i ignored]
+       $0 -h
+EOF
+}
+
+# Not all rc(8) services provide the status command. In general, that's a good
+# (but not ideal) indication of which services are long-running programs like
+# web servers.
+list_services_with_status() {
+
+	service -e | xargs -n 1 -J {} -- {} 2>&1 1>/dev/null | awk '/status/{print $2}'
+}
+
+# SYNOPSIS
+#	filter_ignored_services "all_services" "ignored_services"
+filter_ignored_services() {
+	_all_services="$1"
+	shift
+	_ignored_services="$1"
+	shift
+
+	if [ "$_ignored_services" = "" ]; then
+		printf '%s\n' "$_all_services"
+	else
+		# Assemble a grep invocation that filters out all the ignored
+		# services.
+		set -x
+		set -- grep -v
+		for _is in $_ignored_services; do
+			set -- "$@" -e "$_is"
+		done
+		printf '%s\n' $_all_services | "$@"
+	fi
+}
+
+#
+# Preambule
+#
+
+set -u
+
+#
+# Parse command-line arguments.
+#
+
+ignored_services=""
+OPTIND=1
+while getopts hi: opt; do
+	case "$opt" in
+	h)
+		help
+		exit 0
+		;;
+	i)
+		ignored_services="$OPTARG"
+		;;
+	?)
+		exit 1
+		;;
+	esac
+done
+if [ "$OPTIND" -ne 0 ]; then
+	shift "$(( OPTIND - 1 ))"
+fi
+
+#
+# Main
+#
+
+unfiltered_services=$(list_services_with_status)
+services=$(filter_ignored_services "$unfiltered_services" "$ignored_services")
+
+echo '# HELP freebsd_rc_service_status Status of a FreeBSD rc(8) service.'
+echo '# TYPE freebsd_rc_service_status gauge'
+
+for s in $services; do
+	$s quietstatus >/dev/null 2>&1
+	isrunning="$?"
+	echo "freebsd_rc_service_status{path=\"${s}\"} ${isrunning}"
+done