Add IMGPROXY_PROMETHEUS_NAMESPACE config (#405)

* Add IMGPROXY_PROMETHEUS_NAMESPACE config

* Add documentations about IMGPROXY_PROMETHEUS_NAMESPACE

Co-authored-by: Alexey Remizov <alexey.remizov@sport24.ru>

config.go

@@ -231,7 +231,8 @@ type config struct {
 	NewRelicAppName string
 	NewRelicKey     string
 
-	PrometheusBind string
+	PrometheusBind      string
+	PrometheusNamespace string
 
 	BugsnagKey        string
 	BugsnagStage      string
@@ -389,6 +390,7 @@ func configure() error {
 	strEnvConfig(&conf.NewRelicKey, "IMGPROXY_NEW_RELIC_KEY")
 
 	strEnvConfig(&conf.PrometheusBind, "IMGPROXY_PROMETHEUS_BIND")
+	strEnvConfig(&conf.PrometheusNamespace, "IMGPROXY_PROMETHEUS_NAMESPACE")
 
 	strEnvConfig(&conf.BugsnagKey, "IMGPROXY_BUGSNAG_KEY")
 	strEnvConfig(&conf.BugsnagStage, "IMGPROXY_BUGSNAG_STAGE")

docs/prometheus.md

@@ -3,7 +3,9 @@
 imgproxy can collect its metrics for Prometheus. To use this feature, do the following:
 
 1. Set `IMGPROXY_PROMETHEUS_BIND` environment variable. Note that you can't bind the main server and Prometheus to the same port;
-2. Collect the metrics from any path on the specified binding.
+2. Set `IMGPROXY_PROMETHEUS_NAMESPACE` to prepend prefix to the names of metrics.
+   I.e. with `IMGPROXY_PROMETHEUS_NAMESPACE=imgproxy` names will look like `imgproxy_requests_total`.  
+3. Collect the metrics from any path on the specified binding.
 
 imgproxy will collect the following metrics:
 

prometheus.go

@@ -32,58 +32,69 @@ func initPrometheus() {
 	}
 
 	prometheusRequestsTotal = prometheus.NewCounter(prometheus.CounterOpts{
-		Name: "requests_total",
-		Help: "A counter of the total number of HTTP requests imgproxy processed.",
+		Namespace: conf.PrometheusNamespace,
+		Name:      "requests_total",
+		Help:      "A counter of the total number of HTTP requests imgproxy processed.",
 	})
 
 	prometheusErrorsTotal = prometheus.NewCounterVec(prometheus.CounterOpts{
-		Name: "errors_total",
-		Help: "A counter of the occurred errors separated by type.",
+		Namespace: conf.PrometheusNamespace,
+		Name:      "errors_total",
+		Help:      "A counter of the occurred errors separated by type.",
 	}, []string{"type"})
 
 	prometheusRequestDuration = prometheus.NewHistogram(prometheus.HistogramOpts{
-		Name: "request_duration_seconds",
-		Help: "A histogram of the response latency.",
+		Namespace: conf.PrometheusNamespace,
+		Name:      "request_duration_seconds",
+		Help:      "A histogram of the response latency.",
 	})
 
 	prometheusDownloadDuration = prometheus.NewHistogram(prometheus.HistogramOpts{
-		Name: "download_duration_seconds",
-		Help: "A histogram of the source image downloading latency.",
+		Namespace: conf.PrometheusNamespace,
+		Name:      "download_duration_seconds",
+		Help:      "A histogram of the source image downloading latency.",
 	})
 
 	prometheusProcessingDuration = prometheus.NewHistogram(prometheus.HistogramOpts{
-		Name: "processing_duration_seconds",
-		Help: "A histogram of the image processing latency.",
+		Namespace: conf.PrometheusNamespace,
+		Name:      "processing_duration_seconds",
+		Help:      "A histogram of the image processing latency.",
 	})
 
 	prometheusBufferSize = prometheus.NewHistogramVec(prometheus.HistogramOpts{
-		Name: "buffer_size_bytes",
-		Help: "A histogram of the buffer size in bytes.",
+		Namespace: conf.PrometheusNamespace,
+		Name:      "buffer_size_bytes",
+		Help:      "A histogram of the buffer size in bytes.",
 	}, []string{"type"})
 
 	prometheusBufferDefaultSize = prometheus.NewGaugeVec(prometheus.GaugeOpts{
-		Name: "buffer_default_size_bytes",
-		Help: "A gauge of the buffer default size in bytes.",
+		Namespace: conf.PrometheusNamespace,
+		Name:      "buffer_default_size_bytes",
+		Help:      "A gauge of the buffer default size in bytes.",
 	}, []string{"type"})
 
 	prometheusBufferMaxSize = prometheus.NewGaugeVec(prometheus.GaugeOpts{
-		Name: "buffer_max_size_bytes",
-		Help: "A gauge of the buffer max size in bytes.",
+		Namespace: conf.PrometheusNamespace,
+		Name:      "buffer_max_size_bytes",
+		Help:      "A gauge of the buffer max size in bytes.",
 	}, []string{"type"})
 
 	prometheusVipsMemory = prometheus.NewGauge(prometheus.GaugeOpts{
-		Name: "vips_memory_bytes",
-		Help: "A gauge of the vips tracked memory usage in bytes.",
+		Namespace: conf.PrometheusNamespace,
+		Name:      "vips_memory_bytes",
+		Help:      "A gauge of the vips tracked memory usage in bytes.",
 	})
 
 	prometheusVipsMaxMemory = prometheus.NewGauge(prometheus.GaugeOpts{
-		Name: "vips_max_memory_bytes",
-		Help: "A gauge of the max vips tracked memory usage in bytes.",
+		Namespace: conf.PrometheusNamespace,
+		Name:      "vips_max_memory_bytes",
+		Help:      "A gauge of the max vips tracked memory usage in bytes.",
 	})
 
 	prometheusVipsAllocs = prometheus.NewGauge(prometheus.GaugeOpts{
-		Name: "vips_allocs",
-		Help: "A gauge of the number of active vips allocations.",
+		Namespace: conf.PrometheusNamespace,
+		Name:      "vips_allocs",
+		Help:      "A gauge of the number of active vips allocations.",
 	})
 
 	prometheus.MustRegister(