4 files changed, 28 insertions, 2 deletions
diff --git a/modules/caddyhttp/app.go b/modules/caddyhttp/app.go
index 4df8689a5..5dbecf9b2 100644
--- a/modules/caddyhttp/app.go
+++ b/modules/caddyhttp/app.go
@@ -198,6 +198,9 @@ func (app *App) Provision(ctx caddy.Context) error {
 		// only enable access logs if configured
 		if srv.Logs != nil {
 			srv.accessLogger = app.logger.Named("log.access")
+			if srv.Logs.Trace {
+				srv.traceLogger = app.logger.Named("log.trace")
+			}
 		}
 
 		// the Go standard library does not let us serve only HTTP/2 using
diff --git a/modules/caddyhttp/logging.go b/modules/caddyhttp/logging.go
index 1fab1e8e8..823763e91 100644
--- a/modules/caddyhttp/logging.go
+++ b/modules/caddyhttp/logging.go
@@ -65,6 +65,17 @@ type ServerLogConfig struct {
 	// and this includes some request and response headers, i.e `Cookie`,
 	// `Set-Cookie`, `Authorization`, and `Proxy-Authorization`.
 	ShouldLogCredentials bool `json:"should_log_credentials,omitempty"`
+
+	// Log each individual handler that is invoked.
+	// Requires that the log emit at DEBUG level.
+	//
+	// NOTE: This may log the configuration of your
+	// HTTP handler modules; do not enable this in
+	// insecure contexts when there is sensitive
+	// data in the configuration.
+	//
+	// EXPERIMENTAL: Subject to change or removal.
+	Trace bool `json:"trace,omitempty"`
 }
 
 // wrapLogger wraps logger in one or more logger named
diff --git a/modules/caddyhttp/routes.go b/modules/caddyhttp/routes.go
index 9db4f2520..6f2371495 100644
--- a/modules/caddyhttp/routes.go
+++ b/modules/caddyhttp/routes.go
@@ -326,8 +326,10 @@ func wrapMiddleware(_ caddy.Context, mh MiddlewareHandler, metrics *Metrics) Mid
 		nextCopy := next
 
 		return HandlerFunc(func(w http.ResponseWriter, r *http.Request) error {
-			// TODO: This is where request tracing could be implemented
-			// TODO: see what the std lib gives us in terms of stack tracing too
+			// EXPERIMENTAL: Trace each module that gets invoked
+			if server, ok := r.Context().Value(ServerCtxKey).(*Server); ok && server != nil {
+				server.logTrace(handlerToUse)
+			}
 			return handlerToUse.ServeHTTP(w, r, nextCopy)
 		})
 	}
diff --git a/modules/caddyhttp/server.go b/modules/caddyhttp/server.go
index 1d621456d..96a819b40 100644
--- a/modules/caddyhttp/server.go
+++ b/modules/caddyhttp/server.go
@@ -234,6 +234,7 @@ type Server struct {
 	logger       *zap.Logger
 	accessLogger *zap.Logger
 	errorLogger  *zap.Logger
+	traceLogger  *zap.Logger
 	ctx          caddy.Context
 
 	server      *http.Server
@@ -738,6 +739,15 @@ func (s *Server) shouldLogRequest(r *http.Request) bool {
 	return !s.Logs.SkipUnmappedHosts
 }
 
+// logTrace will log that this middleware handler is being invoked.
+// It emits at DEBUG level.
+func (s *Server) logTrace(mh MiddlewareHandler) {
+	if s.Logs == nil || !s.Logs.Trace {
+		return
+	}
+	s.traceLogger.Debug(caddy.GetModuleName(mh), zap.Any("module", mh))
+}
+
 // logRequest logs the request to access logs, unless skipped.
 func (s *Server) logRequest(
 	accLog *zap.Logger, r *http.Request, wrec ResponseRecorder, duration *time.Duration,