metrics: move `metrics` up, outside `servers` (#6606)

* metrics: move `metrics`  up, outside `servers`

This change moves the metrics configuration from per-server level to a single config knob within the `http` app. Enabling `metrics` in any of the configured servers inside `http` enables metrics for all servers.

Fix #6604

Signed-off-by: Mohammed Al Sahaf <[email protected]>

* normalize domain name

---------

Signed-off-by: Mohammed Al Sahaf <[email protected]>

3 files changed, 24 insertions, 9 deletions

diff --git a/modules/caddyhttp/app.go b/modules/caddyhttp/app.go
index cd32e72d7..2d221265f 100644
--- a/modules/caddyhttp/app.go
+++ b/modules/caddyhttp/app.go
@@ -15,6 +15,7 @@
 package caddyhttp
 
 import (
+	"cmp"
 	"context"
 	"crypto/tls"
 	"fmt"
@@ -142,6 +143,10 @@ type App struct {
 	// affect functionality.
 	Servers map[string]*Server `json:"servers,omitempty"`
 
+	// If set, metrics observations will be enabled.
+	// This setting is EXPERIMENTAL and subject to change.
+	Metrics *Metrics `json:"metrics,omitempty"`
+
 	ctx    caddy.Context
 	logger *zap.Logger
 	tlsApp *caddytls.TLS
@@ -184,6 +189,10 @@ func (app *App) Provision(ctx caddy.Context) error {
 		return err
 	}
 
+	if app.Metrics != nil {
+		app.Metrics.init = sync.Once{}
+		app.Metrics.httpMetrics = &httpMetrics{}
+	}
 	// prepare each server
 	oldContext := ctx.Context
 	for srvName, srv := range app.Servers {
@@ -196,6 +205,15 @@ func (app *App) Provision(ctx caddy.Context) error {
 		srv.errorLogger = app.logger.Named("log.error")
 		srv.shutdownAtMu = new(sync.RWMutex)
 
+		if srv.Metrics != nil {
+			srv.logger.Warn("per-server 'metrics' is deprecated; use 'metrics' in the root 'http' app instead")
+			app.Metrics = cmp.Or[*Metrics](app.Metrics, &Metrics{
+				init:        sync.Once{},
+				httpMetrics: &httpMetrics{},
+			})
+			app.Metrics.PerHost = app.Metrics.PerHost || srv.Metrics.PerHost
+		}
+
 		// only enable access logs if configured
 		if srv.Logs != nil {
 			srv.accessLogger = app.logger.Named("log.access")
@@ -342,16 +360,11 @@ func (app *App) Provision(ctx caddy.Context) error {
 				srv.listenerWrappers = append([]caddy.ListenerWrapper{new(tlsPlaceholderWrapper)}, srv.listenerWrappers...)
 			}
 		}
-
 		// pre-compile the primary handler chain, and be sure to wrap it in our
 		// route handler so that important security checks are done, etc.
 		primaryRoute := emptyHandler
 		if srv.Routes != nil {
-			if srv.Metrics != nil {
-				srv.Metrics.init = sync.Once{}
-				srv.Metrics.httpMetrics = &httpMetrics{}
-			}
-			err := srv.Routes.ProvisionHandlers(ctx, srv.Metrics)
+			err := srv.Routes.ProvisionHandlers(ctx, app.Metrics)
 			if err != nil {
 				return fmt.Errorf("server %s: setting up route handlers: %v", srvName, err)
 			}
@@ -370,7 +383,7 @@ func (app *App) Provision(ctx caddy.Context) error {
 
 		// provision the named routes (they get compiled at runtime)
 		for name, route := range srv.NamedRoutes {
-			err := route.Provision(ctx, srv.Metrics)
+			err := route.Provision(ctx, app.Metrics)
 			if err != nil {
 				return fmt.Errorf("server %s: setting up named route '%s' handlers: %v", name, srvName, err)
 			}
diff --git a/modules/caddyhttp/metrics.go b/modules/caddyhttp/metrics.go
index 947721429..9bb97e0b4 100644
--- a/modules/caddyhttp/metrics.go
+++ b/modules/caddyhttp/metrics.go
@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"net/http"
+	"strings"
 	"sync"
 	"time"
 
@@ -133,8 +134,8 @@ func (h *metricsInstrumentedHandler) ServeHTTP(w http.ResponseWriter, r *http.Re
 	statusLabels := prometheus.Labels{"server": server, "handler": h.handler, "method": method, "code": ""}
 
 	if h.metrics.PerHost {
-		labels["host"] = r.Host
-		statusLabels["host"] = r.Host
+		labels["host"] = strings.ToLower(r.Host)
+		statusLabels["host"] = strings.ToLower(r.Host)
 	}
 
 	inFlight := h.metrics.httpMetrics.requestInFlight.With(labels)
diff --git a/modules/caddyhttp/server.go b/modules/caddyhttp/server.go
index 96001c6f9..24fecfd88 100644
--- a/modules/caddyhttp/server.go
+++ b/modules/caddyhttp/server.go
@@ -226,6 +226,7 @@ type Server struct {
 
 	// If set, metrics observations will be enabled.
 	// This setting is EXPERIMENTAL and subject to change.
+	// DEPRECATED: Use the app-level `metrics` field.
 	Metrics *Metrics `json:"metrics,omitempty"`
 
 	name string