Add prometheus metric requests_total with headers

Co-authored-by: Julien Salleyron <julien.salleyron@gmail.com>

docs/content/reference/static-configuration/cli-ref.md

@@ -354,6 +354,9 @@ Buckets for latency metrics. (Default: ```0.100000, 0.300000, 1.200000, 5.000000
 `--metrics.prometheus.entrypoint`:  
 EntryPoint (Default: ```traefik```)
 
+`--metrics.prometheus.headerlabels.<name>`:  
+Defines the extra labels for the requests_total metrics, and for each of them, the request header containing the value for this label.
+
 `--metrics.prometheus.manualrouting`:  
 Manual routing (Default: ```false```)
 

docs/content/reference/static-configuration/env-ref.md

@@ -354,6 +354,9 @@ Buckets for latency metrics. (Default: ```0.100000, 0.300000, 1.200000, 5.000000
 `TRAEFIK_METRICS_PROMETHEUS_ENTRYPOINT`:  
 EntryPoint (Default: ```traefik```)
 
+`TRAEFIK_METRICS_PROMETHEUS_HEADERLABELS_<NAME>`:  
+Defines the extra labels for the requests_total metrics, and for each of them, the request header containing the value for this label.
+
 `TRAEFIK_METRICS_PROMETHEUS_MANUALROUTING`:  
 Manual routing (Default: ```false```)
 

docs/content/reference/static-configuration/file.toml

@@ -272,6 +272,9 @@
     addServicesLabels = true
     entryPoint = "foobar"
     manualRouting = true
+    [metrics.prometheus.headerLabels]
+      label1 = "foobar"
+      label2 = "foobar"
   [metrics.datadog]
     address = "foobar"
     pushInterval = "42s"

docs/content/reference/static-configuration/file.yaml

@@ -298,6 +298,9 @@ metrics:
     addServicesLabels: true
     entryPoint: foobar
     manualRouting: true
+    headerLabels:
+      label1: foobar
+      label2: foobar
   datadog:
     address: foobar
     pushInterval: 42s