feature implement constant labels (#542)

Co-authored-by: Aleksey Smirnov <ale.p.smirnov@tbank.ru>

Author: lioshik

config/README.md

@@ -7,6 +7,7 @@
  - `<networks>`: string value consisting of IP, IP mask or named group, for example `"127.0.0.1"` or `"127.0.0.1/24"`.
  - `<host_name>`: string value consisting of host name, for example `"example.com"`
  - `<byte_size>`: string value matching the regular expression `/^\d+(\.\d+)?[KMGTP]?B?$/i`, for example `"100MB"`
+ - `<map[label_name]label_value>`: а map consisting of string keys and string values for optional custom labels in metrics
 
 ### Global configuration consist of:
 ```yml
@@ -237,6 +238,9 @@ allowed_networks: <network_groups>, <networks> ... | optional
 
 # Prometheus metric namespace
 namespace: <string> | optional
+
+# Labels that should be added to each sent prometheus metrics
+constant_labels: <map[label_name]label_value>
 ```
 
 ### <user_config>

config/config.go

@@ -492,6 +492,9 @@ type Metrics struct {
 	// Prometheus metric namespace
 	Namespace string `yaml:"namespace,omitempty"`
 
+	// Constant labels which will be added to each sent prometheus metric
+	ConstantLabels map[string]string `yaml:"constant_labels,omitempty"`
+
 	// Catches all undefined fields and must be empty after parsing.
 	XXX map[string]interface{} `yaml:",inline"`
 }

docs/src/content/docs/cn/index.md

@@ -487,6 +487,8 @@ server:
   # By default access to `/metrics` is unrestricted.
   metrics:
     allowed_networks: ["office"]
+    # You can specify constant labels which will be added to each sent prometheus metric
+    constant_labels: {}
 
 # Configs for input users.
 users:

docs/src/content/docs/configuration/default.md

@@ -177,6 +177,8 @@ server:
   metrics:
     allowed_networks: ["office"]
     namespace: ""
+    # You can specify constant labels which will be added to each sent prometheus metric
+    constant_labels: {}
 
   # Proxy settings enable parsing proxy headers in cases where
   # CHProxy is run behind another proxy.

internal/topology/metrics.go

@@ -13,19 +13,23 @@ var (
 
 func initMetrics(cfg *config.Config) {
 	namespace := cfg.Server.Metrics.Namespace
+	constLabels := cfg.Server.Metrics.ConstantLabels
+
 	HostHealth = prometheus.NewGaugeVec(
 		prometheus.GaugeOpts{
-			Namespace: namespace,
-			Name:      "host_health",
-			Help:      "Health state of hosts by clusters",
+			Namespace:   namespace,
+			Name:        "host_health",
+			Help:        "Health state of hosts by clusters",
+			ConstLabels: constLabels,
 		},
 		[]string{"cluster", "replica", "cluster_node"},
 	)
 	HostPenalties = prometheus.NewCounterVec(
 		prometheus.CounterOpts{
-			Namespace: namespace,
-			Name:      "host_penalties_total",
-			Help:      "Total number of given penalties by host",
+			Namespace:   namespace,
+			Name:        "host_penalties_total",
+			Help:        "Total number of given penalties by host",
+			ConstLabels: constLabels,
 		},
 		[]string{"cluster", "replica", "cluster_node"},
 	)

main_test.go

@@ -640,7 +640,16 @@ func TestServe(t *testing.T) {
 			"testdata/http.metrics.namespace.yml",
 			func(t *testing.T) {
 				resp := httpGet(t, "http://127.0.0.1:9090/metrics", http.StatusOK)
-				assert.GreaterOrEqual(t, len(getStringFromResponse(t, resp.Body)), 10000)
+				metricsString := getStringFromResponse(t, resp.Body)
+				assert.GreaterOrEqual(t, len(metricsString), 10000)
+				assert.GreaterOrEqual(
+					t,
+					strings.Count(
+						metricsString,
+						`constant_label1="value1",constant_label2="value2"`,
+					),
+					10,
+				)
 				resp.Body.Close()
 			},
 			startHTTP,
@@ -973,6 +982,11 @@ func TestServe(t *testing.T) {
 	}
 
 	cfg := &config.Config{}
+	cfg.Server.Metrics.ConstantLabels = map[string]string{
+		"constant_label1": "value1",
+		"constant_label2": "value2",
+	}
+
 	registerMetrics(cfg)
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {