Remake Prometheus endpoint into a proper endpoint module

internal/endpoint/openmetrics/om.go

@@ -0,0 +1,106 @@
+/*
+Maddy Mail Server - Composable all-in-one email server.
+Copyright © 2019-2020 Max Mazurov <fox.cpp@disroot.org>, Maddy Mail Server contributors
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+package openmetrics
+
+import (
+	"fmt"
+	"net"
+	"net/http"
+	"sync"
+
+	"github.com/foxcpp/maddy/framework/config"
+	"github.com/foxcpp/maddy/framework/log"
+	"github.com/foxcpp/maddy/framework/module"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+const modName = "openmetrics"
+
+type Endpoint struct {
+	addrs  []string
+	logger log.Logger
+
+	listenersWg sync.WaitGroup
+	serv        http.Server
+	mux         *http.ServeMux
+}
+
+func New(_ string, args []string) (module.Module, error) {
+	return &Endpoint{
+		addrs:  args,
+		logger: log.Logger{Name: modName, Debug: log.DefaultLogger.Debug},
+	}, nil
+}
+
+func (e *Endpoint) Init(cfg *config.Map) error {
+	cfg.Bool("debug", false, false, &e.logger.Debug)
+	if _, err := cfg.Process(); err != nil {
+		return err
+	}
+
+	e.mux = http.NewServeMux()
+	e.mux.Handle("/metrics", promhttp.Handler())
+	e.serv.Handler = e.mux
+
+	for _, a := range e.addrs {
+		a := a
+		endp, err := config.ParseEndpoint(a)
+		if err != nil {
+			return fmt.Errorf("%s: malformed endpoint: %v", modName, err)
+		}
+		if endp.IsTLS() {
+			return fmt.Errorf("%s: TLS is not supported yet", modName)
+		}
+		l, err := net.Listen(endp.Network(), endp.Address())
+		if err != nil {
+			return fmt.Errorf("%s: %v", modName, err)
+		}
+
+		e.listenersWg.Add(1)
+		go func() {
+			e.logger.Println("listening on", endp.String())
+			err := e.serv.Serve(l)
+			if err != nil && err != http.ErrServerClosed {
+				e.logger.Error("serve failed", err, "endpoint", a)
+			}
+		}()
+	}
+
+	return nil
+}
+
+func (e *Endpoint) Name() string {
+	return modName
+}
+
+func (e *Endpoint) InstanceName() string {
+	return ""
+}
+
+func (e *Endpoint) Close() error {
+	if err := e.serv.Close(); err != nil {
+		return err
+	}
+	e.listenersWg.Wait()
+	return nil
+}
+
+func init() {
+	module.RegisterEndpoint(modName, New)
+}

internal/endpoint/smtp/metrics.go

@@ -72,7 +72,7 @@ var (
 			Namespace: "maddy",
 			Subsystem: "smtp",
 			Name:      "failed_commands",
-			Help:      "Messages rejected with 4xx code due to ratelimiting",
+			Help:      "Failed transaction commands (MAIL, RCPT, DATA)",
 		},
 		[]string{"module", "command", "smtp_code", "smtp_enchcode"},
 	)