Modified Prometheus extension to support adding a prefix to metric names (#13272)

* Modified Prometheus extension to allow for a configurable prefix on metric names.

* Added reference in config_definitions.json and updated docs.

* Fixed whitespace in config_definitions.json.

* Added reference to prometheus.prefix in settings.php

* Defined prefix var as private in Prometheus.php

LibreNMS/Data/Store/Prometheus.php

@@ -38,6 +38,7 @@ class Prometheus extends BaseDatastore
     private $base_uri;
     private $default_opts;
     private $enabled;
+    private $prefix;
 
     public function __construct(\GuzzleHttp\Client $client)
     {
@@ -47,6 +48,10 @@ class Prometheus extends BaseDatastore
         $url = Config::get('prometheus.url');
         $job = Config::get('prometheus.job', 'librenms');
         $this->base_uri = "$url/metrics/job/$job/instance/";
+        $this->prefix = Config::get('prometheus.prefix', '');
+        if ($this->prefix) {
+            $this->prefix = "$this->prefix" . '_';
+        }
 
         $this->default_opts = [
             'headers' => ['Content-Type' => 'text/plain'],
@@ -82,7 +87,7 @@ class Prometheus extends BaseDatastore
 
             foreach ($fields as $k => $v) {
                 if ($v !== null) {
-                    $vals .= "$k $v\n";
+                    $vals .= $this->prefix . "$k $v\n";
                 }
             }
 

doc/Extensions/metrics/Prometheus.md

@@ -34,8 +34,30 @@ continue to function as normal.
 $config['prometheus']['enable'] = true;
 $config['prometheus']['url'] = 'http://127.0.0.1:9091';
 $config['prometheus']['job'] = 'librenms'; # Optional
+$config['prometheus']['prefix'] = 'librenms'; # Optional
 ```
 
+## Prefix
+
+Setting the 'prefix' option will cause all metric names to begin with 
+the configured value.
+
+For instance without setting this option metric names will be something 
+like this:
+
+OUTUCASTPKTS
+ifOutUcastPkts_rate
+INOCTETS
+ifInErrors_rate
+
+Configuring a prefix name, for example 'librenms', instead caused those 
+metrics to be exposed with the following names:
+
+librenms_OUTUCASTPKTS
+librenms_ifOutUcastPkts_rate
+librenms_INOCTETS
+librenms_ifInErrors_rate
+
 ## Sample Prometheus Scrape Config (for scraping the Push Gateway)
 
 ```yml

misc/config_definitions.json

@@ -4771,6 +4771,13 @@
             "section": "prometheus",
             "order": 3
         },
+        "prometheus.prefix": {
+            "default": "",
+            "type": "text",
+            "group": "poller",
+            "section": "prometheus",
+            "order": 4
+        },
         "public_status": {
             "default": false,
             "group": "auth",

resources/lang/en/settings.php

@@ -1176,6 +1176,10 @@ return [
                 'description' => 'Attach Device sysName',
                 'help' => 'Attach sysName information put to Prometheus.',
             ],
+            'prefix' => [
+                'description' => 'Prefix',
+                'help' => 'Optional text to prepend to exported metric names',
+            ],
         ],
         'public_status' => [
             'description' => 'Show status publicly',