T6477: Add telegraf loki output plugin

data/templates/telegraf/telegraf.j2

@@ -41,6 +41,21 @@
   bucket = "{{ influxdb.bucket }}"
 ### End InfluxDB2 ###
 {% endif %}
+{% if loki is vyos_defined %}
+### Loki ###
+[[outputs.loki]]
+  ## The domain of Loki
+  domain = "{{ loki.url }}:{{ loki.port }}"
+{%     if loki.authentication.username is vyos_defined and loki.authentication.password is vyos_defined  %}
+  ## Basic Authentication
+  username = "{{ loki.authentication.username }}"
+  password = "{{ loki.authentication.password }}"
+{%     endif %}
+{%     if loki.metric_name_label is vyos_defined %}
+metric_name_label = "{{ loki.metric_name_label }}"
+{%     endif %}
+### End Loki ###
+{% endif %}
 {% if prometheus_client is vyos_defined %}
 ### Prometheus ###
 [[outputs.prometheus_client]]

interface-definitions/service_monitoring_telegraf.xml.in

@@ -148,6 +148,39 @@
                   #include <include/url-http-https.xml.i>
                 </children>
               </node>
+              <node name="loki">
+                <properties>
+                  <help>Output plugin Loki</help>
+                </properties>
+                <children>
+                  <node name="authentication">
+                    <properties>
+                      <help>HTTP basic authentication parameters</help>
+                    </properties>
+                    <children>
+                      #include <include/generic-username.xml.i>
+                      #include <include/generic-password.xml.i>
+                    </children>
+                  </node>
+                  <leafNode name="metric-name-label">
+                    <properties>
+                      <help>Metric name label</help>
+                      <valueHelp>
+                        <format>txt</format>
+                        <description>Label to use for the metric name</description>
+                      </valueHelp>
+                      <constraint>
+                        #include <include/constraint/alpha-numeric-hyphen-underscore-dot.xml.i>
+                      </constraint>
+                    </properties>
+                  </leafNode>
+                  #include <include/port-number.xml.i>
+                  <leafNode name="port">
+                    <defaultValue>3100</defaultValue>
+                  </leafNode>
+                  #include <include/url-http-https.xml.i>
+                </children>
+              </node>
               <leafNode name="source">
                 <properties>
                   <help>Source parameters for monitoring</help>

smoketest/scripts/cli/test_service_monitoring_telegraf.py

@@ -17,6 +17,7 @@
 import unittest
 
 from base_vyostest_shim import VyOSUnitTestSHIM
+from vyos.configsession import ConfigSessionError
 
 from vyos.utils.process import process_named_running
 from vyos.utils.file import read_file
@@ -63,5 +64,33 @@ def test_01_basic_config(self):
         for input in inputs:
             self.assertIn(input, config)
 
+    def test_02_loki(self):
+        label = 'r123'
+        loki_url = 'http://localhost'
+        port = '3100'
+        loki_username = 'VyOS'
+        loki_password = 'PassW0Rd_VyOS'
+
+        self.cli_set(base_path + ['loki', 'url', loki_url])
+        self.cli_set(base_path + ['loki', 'port', port])
+        self.cli_set(base_path + ['loki', 'metric-name-label', label])
+
+        self.cli_set(base_path + ['loki', 'authentication', 'username', loki_username])
+        # password not set
+        with self.assertRaises(ConfigSessionError):
+            self.cli_commit()
+        self.cli_set(base_path + ['loki', 'authentication', 'password', loki_password])
+
+        # commit changes
+        self.cli_commit()
+
+        config = read_file(TELEGRAF_CONF)
+        self.assertIn(f'[[outputs.loki]]', config)
+        self.assertIn(f'domain = "{loki_url}:{port}"', config)
+        self.assertIn(f'metric_name_label = "{label}"', config)
+        self.assertIn(f'username = "{loki_username}"', config)
+        self.assertIn(f'password = "{loki_password}"', config)
+
+
 if __name__ == '__main__':
     unittest.main(verbosity=2)

src/conf_mode/service_monitoring_telegraf.py

@@ -1,6 +1,6 @@
 #!/usr/bin/env python3
 #
-# Copyright (C) 2021-2023 VyOS maintainers and contributors
+# 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
@@ -113,6 +113,9 @@ def get_config(config=None):
     if not conf.exists(base + ['azure-data-explorer']):
         del monitoring['azure_data_explorer']
 
+    if not conf.exists(base + ['loki']):
+        del monitoring['loki']
+
     return monitoring
 
 def verify(monitoring):
@@ -159,6 +162,19 @@ def verify(monitoring):
         if 'url' not in monitoring['splunk']:
             raise ConfigError(f'Monitoring splunk "url" is mandatory!')
 
+    # Verify Loki
+    if 'loki' in monitoring:
+        if 'url' not in monitoring['loki']:
+            raise ConfigError(f'Monitoring loki "url" is mandatory!')
+        if 'authentication' in monitoring['loki']:
+            if (
+                'username' not in monitoring['loki']['authentication']
+                or 'password' not in monitoring['loki']['authentication']
+            ):
+                raise ConfigError(
+                    f'Authentication "username" and "password" are mandatory!'
+                )
+
     return None
 
 def generate(monitoring):