caddyhttp: Implement named routes, `invoke` directive (#5107)

* caddyhttp: Implement named routes, `invoke` directive

* gofmt

* Add experimental marker

* Adjust route compile comments

4 files changed, 134 insertions, 19 deletions

diff --git a/modules/caddyhttp/app.go b/modules/caddyhttp/app.go
index 53b5782..0e02afd 100644
--- a/modules/caddyhttp/app.go
+++ b/modules/caddyhttp/app.go
@@ -293,11 +293,19 @@ func (app *App) Provision(ctx caddy.Context) error {
 		if srv.Errors != nil {
 			err := srv.Errors.Routes.Provision(ctx)
 			if err != nil {
-				return fmt.Errorf("server %s: setting up server error handling routes: %v", srvName, err)
+				return fmt.Errorf("server %s: setting up error handling routes: %v", srvName, err)
 			}
 			srv.errorHandlerChain = srv.Errors.Routes.Compile(errorEmptyHandler)
 		}
 
+		// provision the named routes (they get compiled at runtime)
+		for name, route := range srv.NamedRoutes {
+			err := route.Provision(ctx, srv.Metrics)
+			if err != nil {
+				return fmt.Errorf("server %s: setting up named route '%s' handlers: %v", name, srvName, err)
+			}
+		}
+
 		// prepare the TLS connection policies
 		err = srv.TLSConnPolicies.Provision(ctx)
 		if err != nil {
diff --git a/modules/caddyhttp/invoke.go b/modules/caddyhttp/invoke.go
new file mode 100644
index 0000000..97fd1cc
--- /dev/null
+++ b/modules/caddyhttp/invoke.go
@@ -0,0 +1,56 @@
+// Copyright 2015 Matthew Holt and The Caddy Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package caddyhttp
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/caddyserver/caddy/v2"
+)
+
+func init() {
+	caddy.RegisterModule(Invoke{})
+}
+
+// Invoke implements a handler that compiles and executes a
+// named route that was defined on the server.
+//
+// EXPERIMENTAL: Subject to change or removal.
+type Invoke struct {
+	// Name is the key of the named route to execute
+	Name string `json:"name,omitempty"`
+}
+
+// CaddyModule returns the Caddy module information.
+func (Invoke) CaddyModule() caddy.ModuleInfo {
+	return caddy.ModuleInfo{
+		ID:  "http.handlers.invoke",
+		New: func() caddy.Module { return new(Invoke) },
+	}
+}
+
+func (invoke *Invoke) ServeHTTP(w http.ResponseWriter, r *http.Request, next Handler) error {
+	server := r.Context().Value(ServerCtxKey).(*Server)
+	if route, ok := server.NamedRoutes[invoke.Name]; ok {
+		return route.Compile(next).ServeHTTP(w, r)
+	}
+	return fmt.Errorf("invoke: route '%s' not found", invoke.Name)
+}
+
+// Interface guards
+var (
+	_ MiddlewareHandler = (*Invoke)(nil)
+)
diff --git a/modules/caddyhttp/routes.go b/modules/caddyhttp/routes.go
index da25097..9be3d01 100644
--- a/modules/caddyhttp/routes.go
+++ b/modules/caddyhttp/routes.go
@@ -120,6 +120,59 @@ func (r Route) String() string {
 		r.Group, r.MatcherSetsRaw, handlersRaw, r.Terminal)
 }
 
+// Provision sets up both the matchers and handlers in the route.
+func (r *Route) Provision(ctx caddy.Context, metrics *Metrics) error {
+	err := r.ProvisionMatchers(ctx)
+	if err != nil {
+		return err
+	}
+	return r.ProvisionHandlers(ctx, metrics)
+}
+
+// ProvisionMatchers sets up all the matchers by loading the
+// matcher modules. Only call this method directly if you need
+// to set up matchers and handlers separately without having
+// to provision a second time; otherwise use Provision instead.
+func (r *Route) ProvisionMatchers(ctx caddy.Context) error {
+	// matchers
+	matchersIface, err := ctx.LoadModule(r, "MatcherSetsRaw")
+	if err != nil {
+		return fmt.Errorf("loading matcher modules: %v", err)
+	}
+	err = r.MatcherSets.FromInterface(matchersIface)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+// ProvisionHandlers sets up all the handlers by loading the
+// handler modules. Only call this method directly if you need
+// to set up matchers and handlers separately without having
+// to provision a second time; otherwise use Provision instead.
+func (r *Route) ProvisionHandlers(ctx caddy.Context, metrics *Metrics) error {
+	handlersIface, err := ctx.LoadModule(r, "HandlersRaw")
+	if err != nil {
+		return fmt.Errorf("loading handler modules: %v", err)
+	}
+	for _, handler := range handlersIface.([]any) {
+		r.Handlers = append(r.Handlers, handler.(MiddlewareHandler))
+	}
+
+	// pre-compile the middleware handler chain
+	for _, midhandler := range r.Handlers {
+		r.middleware = append(r.middleware, wrapMiddleware(ctx, midhandler, metrics))
+	}
+	return nil
+}
+
+// Compile prepares a middleware chain from the route list.
+// This should only be done once during the request, just
+// before the middleware chain is executed.
+func (r Route) Compile(next Handler) Handler {
+	return wrapRoute(r)(next)
+}
+
 // RouteList is a list of server routes that can
 // create a middleware chain.
 type RouteList []Route
@@ -139,12 +192,7 @@ func (routes RouteList) Provision(ctx caddy.Context) error {
 // to provision a second time; otherwise use Provision instead.
 func (routes RouteList) ProvisionMatchers(ctx caddy.Context) error {
 	for i := range routes {
-		// matchers
-		matchersIface, err := ctx.LoadModule(&routes[i], "MatcherSetsRaw")
-		if err != nil {
-			return fmt.Errorf("route %d: loading matcher modules: %v", i, err)
-		}
-		err = routes[i].MatcherSets.FromInterface(matchersIface)
+		err := routes[i].ProvisionMatchers(ctx)
 		if err != nil {
 			return fmt.Errorf("route %d: %v", i, err)
 		}
@@ -158,25 +206,18 @@ func (routes RouteList) ProvisionMatchers(ctx caddy.Context) error {
 // to provision a second time; otherwise use Provision instead.
 func (routes RouteList) ProvisionHandlers(ctx caddy.Context, metrics *Metrics) error {
 	for i := range routes {
-		handlersIface, err := ctx.LoadModule(&routes[i], "HandlersRaw")
+		err := routes[i].ProvisionHandlers(ctx, metrics)
 		if err != nil {
-			return fmt.Errorf("route %d: loading handler modules: %v", i, err)
-		}
-		for _, handler := range handlersIface.([]any) {
-			routes[i].Handlers = append(routes[i].Handlers, handler.(MiddlewareHandler))
-		}
-
-		// pre-compile the middleware handler chain
-		for _, midhandler := range routes[i].Handlers {
-			routes[i].middleware = append(routes[i].middleware, wrapMiddleware(ctx, midhandler, metrics))
+			return fmt.Errorf("route %d: %v", i, err)
 		}
 	}
 	return nil
 }
 
 // Compile prepares a middleware chain from the route list.
-// This should only be done once: after all the routes have
-// been provisioned, and before serving requests.
+// This should only be done either once during provisioning
+// for top-level routes, or on each request just before the
+// middleware chain is executed for subroutes.
 func (routes RouteList) Compile(next Handler) Handler {
 	mid := make([]Middleware, 0, len(routes))
 	for _, route := range routes {
diff --git a/modules/caddyhttp/server.go b/modules/caddyhttp/server.go
index 411ec72..d2de09b 100644
--- a/modules/caddyhttp/server.go
+++ b/modules/caddyhttp/server.go
@@ -102,6 +102,16 @@ type Server struct {
 	// The error routes work exactly like the normal routes.
 	Errors *HTTPErrorConfig `json:"errors,omitempty"`
 
+	// NamedRoutes describes a mapping of reusable routes that can be
+	// invoked by their name. This can be used to optimize memory usage
+	// when the same route is needed for many subroutes, by having
+	// the handlers and matchers be only provisioned once, but used from
+	// many places. These routes are not executed unless they are invoked
+	// from another route.
+	//
+	// EXPERIMENTAL: Subject to change or removal.
+	NamedRoutes map[string]*Route `json:"named_routes,omitempty"`
+
 	// How to handle TLS connections. At least one policy is
 	// required to enable HTTPS on this server if automatic
 	// HTTPS is disabled or does not apply.