Add static 'site' label to all metrics

README.adoc

@@ -40,7 +40,7 @@ image::examples/grafana.png[Grafana]
 
 === Docker
 
-. `docker run -d --name fronius-exporter -p "8080:8080" quay.io/ccremer/fronius-exporter`
+. `docker run -d --name fronius-exporter -p "8080:8080" quay.io/ccremer/fronius-exporter --help`
 
 === Helm Chart
 
@@ -53,7 +53,7 @@ With https://ccremer.github.io/charts/fronius-exporter[fronius-exporter]
 
 [source,console]
 ----
-fronius-exporter --url http://symo.ip.or.hostname/solar_api/v1/GetPowerFlowRealtimeData.fcgi
+fronius-exporter --symo.url http://symo.ip.or.hostname/solar_api/v1/GetPowerFlowRealtimeData.fcgi --symo.site my-site-name
 ----
 
 Upon each call to `/metrics`, the exporter will do a GET request on the given URL, and translate the JSON response to Prometheus metrics format.
@@ -71,7 +71,7 @@ All flags are also configurable with Environment variables.
 * Replace the `.` delimiter with `__`
 * CLI flags take precedence
 
-.Following calls are requivalent
+.Following calls are equivalent
 ----
 fronius-exporter --symo.url http://...
 SYMO__URL=http://... fronius-exporter

cfg/config.go

@@ -3,6 +3,7 @@ package cfg
 import (
 	"fmt"
 	"net/http"
+	"net/url"
 	"os"
 	"strings"
 	"time"
@@ -33,14 +34,15 @@ func setupCliFlags(version string, fs *flag.FlagSet, config *Configuration) {
 		fmt.Fprintf(os.Stderr, "Usage of %s (%s):\n", os.Args[0], version)
 		fs.PrintDefaults()
 	}
-	fs.String("bind-addr", config.BindAddr, "IP Address to bind to listen for Prometheus scrapes")
-	fs.String("log.level", config.Log.Level, "Logging level")
-	fs.BoolP("log.verbose", "v", config.Log.Verbose, "Shortcut for --log.level=debug")
+	fs.String("bind-addr", config.BindAddr, "IP Address to bind to listen for Prometheus scrapes.")
+	fs.String("log.level", config.Log.Level, "Logging level.")
+	fs.BoolP("log.verbose", "v", config.Log.Verbose, "Shortcut for --log.level=debug.")
 	fs.StringSlice("symo.header", config.Symo.Headers,
-		"List of \"key: value\" headers to append to the requests going to Fronius Symo")
-	fs.StringP("symo.url", "u", config.Symo.URL, "Target URL of Fronius Symo device")
+		"List of \"key: value\" headers to append to the requests going to Fronius Symo. Example: --symo.header \"authorization=Basic <base64>\".")
+	fs.StringP("symo.url", "u", config.Symo.URL, "Target URL of Fronius Symo device.")
+	fs.StringP("symo.site", "s", config.Symo.Site, "Site name of the Fronius Symo device, it's added as a static label to the metrics. Defaults to the hostname in --symo.url.")
 	fs.Int64("symo.timeout", int64(config.Symo.Timeout.Seconds()),
-		"Timeout in seconds when collecting metrics from Fronius Symo. Should not be larger than the scrape interval")
+		"Timeout in seconds when collecting metrics from Fronius Symo. Should not be larger than the scrape interval.")
 
 }
 
@@ -56,6 +58,8 @@ func postLoadProcess(config *Configuration) {
 	}
 	config.Symo.Headers = parsedHeaders
 
+	config.Symo.Site = getSiteOrHostName(config.Symo.Site, config.Symo.URL)
+
 	level, err := log.ParseLevel(config.Log.Level)
 	if err != nil {
 		log.WithError(err).Warn("Could not parse log level, fallback to info level")
@@ -130,3 +134,17 @@ func ConvertHeaders(headers []string, header *http.Header) {
 		header.Set(key, value)
 	}
 }
+
+// getSiteOrHostName returns the site name as it was given in the config.
+// If that's empty, it returns the hostname or IP address given in the Symo URL.
+// If the URL cannot be parsed either, it returns empty string.
+func getSiteOrHostName(site, rawURL string) string {
+	if site != "" {
+		return site
+	}
+	u, err := url.Parse(rawURL)
+	if err != nil {
+		return ""
+	}
+	return u.Host
+}

cfg/config_test.go

@@ -212,3 +212,33 @@ func Test_parseHeaderString(t *testing.T) {
 		})
 	}
 }
+
+func Test_getSiteOrHostName(t *testing.T) {
+	tests := map[string]struct {
+		site     string
+		url      string
+		expected string
+	}{
+		"GivenEmptySite_ThenReturnHostnameFromURL": {
+			site:     "",
+			url:      "http://hostname.tld:8080/somepath",
+			expected: "hostname.tld:8080",
+		},
+		"GivenConfiguredSite_ThenReturnSameValue": {
+			site:     "my-site",
+			url:      "http://hostname.tld:8080/somepath",
+			expected: "my-site",
+		},
+		"GivenEmptySite_WhenUrlInvalid_ThenReturnEmpty": {
+			site:     "",
+			url:      "hostname.tld",
+			expected: "",
+		},
+	}
+	for name, tt := range tests {
+		t.Run(name, func(t *testing.T) {
+			result := getSiteOrHostName(tt.site, tt.url)
+			assert.Equal(t, tt.expected, result)
+		})
+	}
+}

cfg/types.go

@@ -17,6 +17,7 @@ type (
 	// SymoConfig configures the Fronius Symo device
 	SymoConfig struct {
 		URL     string        `koanf:"url"`
+		Site    string        `koanf:"site"`
 		Timeout time.Duration `koanf:"timeout"`
 		Headers []string      `koanf:"header"`
 	}

metrics.go

@@ -12,61 +12,77 @@ import (
 var (
 	namespace           = "fronius"
 	scrapeDurationGauge = promauto.NewGauge(prometheus.GaugeOpts{
-		Namespace: namespace,
-		Name:      "scrape_duration_seconds",
-		Help:      "Time it took to scrape the device in seconds",
+		Namespace:   namespace,
+		Name:        "scrape_duration_seconds",
+		ConstLabels: getConstantLabels(),
+		Help:        "Time it took to scrape the device in seconds",
 	})
 	scrapeErrorCount = promauto.NewCounter(prometheus.CounterOpts{
-		Namespace: namespace,
-		Name:      "scrape_error_count",
-		Help:      "Number of scrape errors",
+		Namespace:   namespace,
+		Name:        "scrape_error_count",
+		ConstLabels: getConstantLabels(),
+		Help:        "Number of scrape errors",
 	})
 
 	inverterPowerGaugeVec = promauto.NewGaugeVec(prometheus.GaugeOpts{
-		Namespace: namespace,
-		Name:      "inverter_power",
-		Help:      "Power flow of the inverter in Watt",
+		Namespace:   namespace,
+		Name:        "inverter_power",
+		ConstLabels: getConstantLabels(),
+		Help:        "Power flow of the inverter in Watt",
 	}, []string{"inverter"})
 
 	sitePowerLoadGauge = promauto.NewGauge(prometheus.GaugeOpts{
-		Namespace: namespace,
-		Name:      "site_power_load",
-		Help:      "Site power load in Watt",
+		Namespace:   namespace,
+		Name:        "site_power_load",
+		ConstLabels: getConstantLabels(),
+		Help:        "Site power load in Watt",
 	})
 	sitePowerGridGauge = promauto.NewGauge(prometheus.GaugeOpts{
-		Namespace: namespace,
-		Name:      "site_power_grid",
-		Help:      "Site power supplied to or provided from the grid in Watt",
+		Namespace:   namespace,
+		Name:        "site_power_grid",
+		ConstLabels: getConstantLabels(),
+		Help:        "Site power supplied to or provided from the grid in Watt",
 	})
 	sitePowerAccuGauge = promauto.NewGauge(prometheus.GaugeOpts{
-		Namespace: namespace,
-		Name:      "site_power_accu",
-		Help:      "Site power supplied to or provided from the accumulator(s) in Watt",
+		Namespace:   namespace,
+		Name:        "site_power_accu",
+		ConstLabels: getConstantLabels(),
+		Help:        "Site power supplied to or provided from the accumulator(s) in Watt",
 	})
 	sitePowerPhotovoltaicsGauge = promauto.NewGauge(prometheus.GaugeOpts{
-		Namespace: namespace,
-		Name:      "site_power_photovoltaic",
-		Help:      "Site power supplied to or provided from the accumulator(s) in Watt",
+		Namespace:   namespace,
+		Name:        "site_power_photovoltaic",
+		ConstLabels: getConstantLabels(),
+		Help:        "Site power supplied to or provided from the accumulator(s) in Watt",
 	})
 
 	siteAutonomyRatioGauge = promauto.NewGauge(prometheus.GaugeOpts{
-		Namespace: namespace,
-		Name:      "site_autonomy_ratio",
-		Help:      "Relative autonomy ratio of the site",
+		Namespace:   namespace,
+		Name:        "site_autonomy_ratio",
+		ConstLabels: getConstantLabels(),
+		Help:        "Relative autonomy ratio of the site",
 	})
 	siteSelfConsumptionRatioGauge = promauto.NewGauge(prometheus.GaugeOpts{
-		Namespace: namespace,
-		Name:      "site_selfconsumption_ratio",
-		Help:      "Relative self consumption ratio of the site",
+		Namespace:   namespace,
+		Name:        "site_selfconsumption_ratio",
+		ConstLabels: getConstantLabels(),
+		Help:        "Relative self consumption ratio of the site",
 	})
 
 	siteEnergyGaugeVec = promauto.NewGaugeVec(prometheus.GaugeOpts{
-		Namespace: namespace,
-		Name:      "site_energy_consumption",
-		Help:      "Energy consumption in kWh",
+		Namespace:   namespace,
+		Name:        "site_energy_consumption",
+		ConstLabels: getConstantLabels(),
+		Help:        "Energy consumption in kWh",
 	}, []string{"time_frame"})
 )
 
+func getConstantLabels() prometheus.Labels {
+	return map[string]string{
+		"site": config.Symo.Site,
+	}
+}
+
 func collectMetricsFromTarget(client *fronius.SymoClient) {
 	start := time.Now()
 	log.WithFields(log.Fields{