feat: Add labels for label-based metric scraping

Add prometheus.io labels to compose.metrics.yml so monitoring-ng can
auto-discover and scrape Traefik's metrics on the internal network when
enabled.

.env.sample

@@ -139,10 +139,14 @@ WRITE_TIMEOUT=0s
 #####################################################################
 
 ## Enable prometheus metrics collection
-## used used by the coop-cloud monitoring stack
-## BASIC_AUTH should also be enabled
+## Metrics are served unauthenticated on :8082, reachable only from
+## other services on the proxy network (e.g. monitoring-ng's Alloy,
+## which auto-discovers it via the prometheus.io/scrape label)
 #COMPOSE_FILE="$COMPOSE_FILE:compose.metrics.yml"
 #METRICS_ENABLED=1
+
+## Setting METRICS_FQDN also adds a public metrics endpoint (behind
+## basic auth). BASIC_AUTH should be enabled for this.
 #METRICS_FQDN=metrics.traefik.example.com
 
 #####################################################################
@@ -235,11 +239,3 @@ WRITE_TIMEOUT=0s
 
 ## Access logs
 #COMPOSE_FILE="$COMPOSE_FILE:compose.access-log.yml"
-
-## Behind a reverse proxy
-#
-# YAML array of subnets from which Traefik's trusts the x-real-ip
-# header when behind a reverse proxy.
-#
-# https://doc.traefik.io/traefik/reference/install-configuration/entrypoints/#opt-forwardedHeaders-trustedIPs
-#TRUSTED_IPS="['10.13.12.1']" # 10.13.12.1 is an example

abra.sh

@@ -1,4 +1,4 @@
-export TRAEFIK_YML_VERSION=v34
-export FILE_PROVIDER_YML_VERSION=v12
+export TRAEFIK_YML_VERSION=v35
+export FILE_PROVIDER_YML_VERSION=v13
 export ENTRYPOINT_VERSION=v5
 export ANUBIS_YML_VERSION=v1

compose.metrics.yml

@@ -3,3 +3,9 @@ services:
   app:
     environment:
       - METRICS_ENABLED
+    deploy:
+      labels:
+        # lets monitoring-ng's Alloy auto-discover and scrape metrics-internal
+        # via the proxy network.
+        - "prometheus.io/scrape=true"
+        - "prometheus.io/port=8082"

file-provider.yml.tmpl

@@ -32,6 +32,7 @@ http:
         stsSeconds: "31536000"
   {{ if eq (env "METRICS_ENABLED") "1" }}
   routers:
+    {{ if ne (env "METRICS_FQDN") "" }}
     traefik-metrics:
       rule: "Host(`{{ env "METRICS_FQDN" }}`)"
       entrypoints:
@@ -41,6 +42,14 @@ http:
       middlewares:
         - basicauth@file
       service: prometheus@internal
+    {{ end }}
+    # reachable from other services on the proxy network only (this port
+    # isn't published to the host), without auth
+    traefik-metrics-internal:
+      rule: "PathPrefix(`/`)"
+      entrypoints:
+        - metrics-internal
+      service: prometheus@internal
   {{ end }}
 
 tls:

release/next

@@ -0,0 +1 @@
+1. compose.metrics.yml now adds prometheus.io/scrape labels so services like monitoring-ng can automatically discover and scrape Traefik's metrics.

traefik.yml.tmpl

@@ -48,10 +48,6 @@ entrypoints:
           to: web-secure
   web-secure:
     address: ":443"
-{{ if ne (env "TRUSTED_IPS") "" }}
-    forwardedHeaders:
-      trustedIPs: {{ env "TRUSTED_IPS" }}
-{{ end }}
     transport:
       respondingTimeouts:
         readTimeout: {{ env "READ_TIMEOUT" }}
@@ -131,6 +127,10 @@ entrypoints:
   onion:
     address: ":9052"
   {{- end }}
+  {{- if eq (env "METRICS_ENABLED") "1" }}
+  metrics-internal:
+    address: ":8082"
+  {{- end }}
 
 ping:
   entryPoint: web