T973: add basic node_exporter implementation

data/templates/node_exporter/node_exporter.service.j2

@@ -0,0 +1,17 @@
+{% set vrf_command = 'ip vrf exec ' ~ vrf ~ ' runuser -u node_exporter -- ' if vrf is vyos_defined else '' %}
+[Unit]
+Description=Node Exporter
+Documentation=https://github.com/prometheus/node_exporter
+After=network.target
+
+[Service]
+{% if vrf is not vyos_defined %}
+User=node_exporter
+{% endif %}
+ExecStart={{ vrf_command }}/usr/sbin/node_exporter \
+{% for address in listen_address %}
+        --web.listen-address={{ address }}:{{ port }}
+{% endfor %}
+
+[Install]
+WantedBy=multi-user.target

debian/vyos-1x.postinst

@@ -21,6 +21,11 @@ if ! grep -q '^openvpn' /etc/passwd; then
     adduser --quiet --firstuid 100 --system --group --shell /usr/sbin/nologin openvpn
 fi
 
+# node_exporter should get its own user
+if ! grep -q '^node_exporter' /etc/passwd; then
+    adduser --quiet --firstuid 100 --system --group --shell /bin/false node_exporter
+fi
+
 # We need to have a group for RADIUS service users to use it inside PAM rules
 if ! grep -q '^radius' /etc/group; then
     addgroup --firstgid 1000 --quiet radius

interface-definitions/service_monitoring_node_exporter.xml.in

@@ -0,0 +1,28 @@
+<?xml version="1.0"?>
+<interfaceDefinition>
+  <node name="service">
+    <children>
+      <node name="monitoring">
+        <children>
+          <node name="node-exporter" owner="${vyos_conf_scripts_dir}/service_monitoring_node-exporter.py">
+            <properties>
+              <help>Prometheus exporter for hardware and operating system metrics</help>
+              <priority>1280</priority>
+            </properties>
+            <children>
+              #include <include/listen-address.xml.i>
+              <leafNode name="listen-address">
+                <defaultValue>0.0.0.0</defaultValue>
+              </leafNode>
+              #include <include/port-number.xml.i>
+              <leafNode name="port">
+                <defaultValue>9100</defaultValue>
+              </leafNode>
+              #include <include/interface/vrf.xml.i>
+            </children>
+          </node>
+        </children>
+      </node>
+    </children>
+  </node>
+</interfaceDefinition>

smoketest/scripts/cli/test_service_monitoring_node-exporter.py

@@ -0,0 +1,64 @@
+#!/usr/bin/env python3
+#
+# Copyright (C) 2020-2024 VyOS maintainers and contributors
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 or later as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import unittest
+
+from base_vyostest_shim import VyOSUnitTestSHIM
+from vyos.utils.process import process_named_running
+from vyos.utils.file import read_file
+
+PROCESS_NAME = 'node_exporter'
+base_path = ['service', 'monitoring', 'node-exporter']
+service_file = '/etc/systemd/system/node_exporter.service'
+listen_if = 'dum3421'
+listen_ip = '192.0.2.1'
+
+
+class TestMonitoringNodeExporter(VyOSUnitTestSHIM.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        # call base-classes classmethod
+        super(TestMonitoringNodeExporter, cls).setUpClass()
+        # create a test interfaces
+        cls.cli_set(
+            cls, ['interfaces', 'dummy', listen_if, 'address', listen_ip + '/32']
+        )
+
+    @classmethod
+    def tearDownClass(cls):
+        cls.cli_delete(cls, ['interfaces', 'dummy', listen_if])
+        super(TestMonitoringNodeExporter, cls).tearDownClass()
+
+    def tearDown(self):
+        self.cli_delete(base_path)
+        self.cli_commit()
+        self.assertFalse(process_named_running(PROCESS_NAME))
+
+    def test_01_basic_config(self):
+        self.cli_set(base_path + ['listen-address', listen_ip])
+
+        # commit changes
+        self.cli_commit()
+
+        file_content = read_file(service_file)
+        self.assertIn(f'{listen_ip}:9100', file_content)
+
+        # Check for running process
+        self.assertTrue(process_named_running(PROCESS_NAME))
+
+
+if __name__ == '__main__':
+    unittest.main(verbosity=2)

src/conf_mode/service_monitoring_node-exporter.py

@@ -0,0 +1,104 @@
+#!/usr/bin/env python3
+#
+# Copyright (C) 2021-2024 VyOS maintainers and contributors
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 or later as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import os
+
+from sys import exit
+
+from vyos.config import Config
+from vyos.configdict import is_node_changed
+from vyos.configverify import verify_vrf
+from vyos.template import render
+from vyos.utils.process import call
+from vyos import ConfigError
+from vyos import airbag
+
+
+airbag.enable()
+
+service_file = '/etc/systemd/system/node_exporter.service'
+systemd_service = 'node_exporter.service'
+
+
+def get_config(config=None):
+    if config:
+        conf = config
+    else:
+        conf = Config()
+    base = ['service', 'monitoring', 'node-exporter']
+    if not conf.exists(base):
+        return None
+
+    config_data = conf.get_config_dict(
+        base, key_mangling=('-', '_'), get_first_key=True
+    )
+    config_data = conf.merge_defaults(config_data, recursive=True)
+
+    tmp = is_node_changed(conf, base + ['vrf'])
+    if tmp:
+        config_data.update({'restart_required': {}})
+
+    return config_data
+
+
+def verify(config_data):
+    # bail out early - looks like removal from running config
+    if not config_data:
+        return None
+
+    verify_vrf(config_data)
+    return None
+
+
+def generate(config_data):
+    if not config_data:
+        # Delete systemd files
+        if os.path.isfile(service_file):
+            os.unlink(service_file)
+        return None
+
+    # Render node_exporter service_file
+    render(service_file, 'node_exporter/node_exporter.service.j2', config_data)
+    return None
+
+
+def apply(config_data):
+    # Reload systemd manager configuration
+    call('systemctl daemon-reload')
+    if not config_data:
+        call(f'systemctl stop {systemd_service}')
+        return
+
+    # we need to restart the service if e.g. the VRF name changed
+    systemd_action = 'reload-or-restart'
+    if 'restart_required' in config_data:
+        systemd_action = 'restart'
+
+    call(f'systemctl {systemd_action} {systemd_service}')
+
+    # Telegraf include custom rsyslog config changes
+    call('systemctl reload-or-restart rsyslog')
+
+
+if __name__ == '__main__':
+    try:
+        c = get_config()
+        verify(c)
+        generate(c)
+        apply(c)
+    except ConfigError as e:
+        print(e)
+        exit(1)