Remake Prometheus endpoint into a proper endpoint module

.mkdocs.yml

@@ -24,6 +24,7 @@ nav:
   - unicode.md
   - upgrading.md
   - specifications.md
+  - openmetrics.md
   - Manual pages:
     - man/_generated_maddy.1.md
     - man/_generated_maddy-auth.5.md

docs/man/maddy.5.scd

@@ -181,6 +181,17 @@ logrotate daemon. Send SIGUSR1 to maddy process to make it reopen log files.
 Enable verbose logging for all modules. You don't need that unless you are
 reporting a bug.
 
+# Prometheus/OpenMetrics endpoint
+
+```
+openmetrics tcp://127.0.0.1:9749 { }
+```
+
+This will enable HTTP listener that will serve telemetry in OpenMetrics format.
+(It is compatible with Prometheus).
+
+See openmetrics.md documentation page the list of metrics exposed.
+
 # Signals
 
 *SIGTERM, SIGINT, SIGHUP*

docs/openmetrics.md

@@ -0,0 +1,40 @@
+# OpenMetrics/Promethus telemetry
+
+Various server statistics is provided in OpenMetrics format by "openmetrics"
+module.
+
+To enable it, add following line to the server config:
+```
+openmetrics tcp://127.0.0.1:9749 { }
+```
+
+Scrape endpoint would be `http://127.0.0.1:9749/metrics`.
+
+## Metrics
+
+```
+# AUTH command failures due to invalid credentials.
+maddy_smtp_failed_logins{module}
+# Failed SMTP transaction commands (MAIL, RCPT, DATA).
+maddy_smtp_failed_commands{module, command, smtp_code, smtp_enchcode}
+# Messages rejected with 4xx code due to ratelimiting.
+maddy_smtp_ratelimit_deferred{module}
+# Amount of started SMTP trasanactions started.
+maddy_smtp_started_transactions{module}
+# Amount of aborted SMTP trasanactions started.
+maddy_smtp_aborted_transactions{module}
+# Amount of completed SMTP trasanactions.
+maddy_smtp_completed_transactions{module}
+# Number of times a check returned 'reject' result (may be more than processed
+# messages if check does so on per-recipient basis)
+maddy_check_reject{check}
+# Number of times a check returned 'quarantine' result (may be more than
+# processed messages if check does so on per-recipient basis).
+maddy_check_quarantined{check}
+# Amount of queued messages
+maddy_queue_length{module, location}
+# Outbound connections established with specific TLS security level
+maddy_remote_conns_tls_level{module, level}
+# Outbound connections established with specific MX security level
+maddy_remote_conns_mx_level{module, level}
+```

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"},
 	)

maddy.go

@@ -23,7 +23,6 @@ import (
 	"flag"
 	"fmt"
 	"io"
-	"net"
 	"net/http"
 	"os"
 	"path/filepath"
@@ -37,7 +36,6 @@ import (
 	"github.com/foxcpp/maddy/framework/hooks"
 	"github.com/foxcpp/maddy/framework/log"
 	"github.com/foxcpp/maddy/framework/module"
-	"github.com/prometheus/client_golang/prometheus/promhttp"
 
 	// Import packages for side-effect of module registration.
 	_ "github.com/foxcpp/maddy/internal/auth/dovecot_sasl"
@@ -56,6 +54,7 @@ import (
 	_ "github.com/foxcpp/maddy/internal/check/spf"
 	_ "github.com/foxcpp/maddy/internal/endpoint/dovecot_sasld"
 	_ "github.com/foxcpp/maddy/internal/endpoint/imap"
+	_ "github.com/foxcpp/maddy/internal/endpoint/openmetrics"
 	_ "github.com/foxcpp/maddy/internal/endpoint/smtp"
 	_ "github.com/foxcpp/maddy/internal/imap_filter"
 	_ "github.com/foxcpp/maddy/internal/imap_filter/command"
@@ -116,8 +115,6 @@ var (
 	profileEndpoint   *string
 	blockProfileRate  *int
 	mutexProfileFract *int
-
-	prometheusEndpoint string
 )
 
 func BuildInfo() string {
@@ -226,25 +223,6 @@ func initDebug() {
 	}
 }
 
-func startPrometheusHTTP(endpoint string) error {
-	mux := http.NewServeMux()
-	mux.Handle("/metrics", promhttp.Handler())
-
-	l, err := net.Listen("tcp", prometheusEndpoint)
-	if err != nil {
-		return err
-	}
-
-	log.Println("listening on", prometheusEndpoint, "for Prometheus scraping")
-	go func() {
-		err := http.Serve(l, mux)
-		if err != nil && err != http.ErrServerClosed {
-			log.Println("prometheus listener fail:", err)
-		}
-	}()
-	return nil
-}
-
 func InitDirs() error {
 	if config.StateDirectory == "" {
 		config.StateDirectory = DefaultStateDirectory
@@ -304,7 +282,6 @@ func ReadGlobals(cfg []config.Node) (map[string]interface{}, []config.Node, erro
 	globals := config.NewMap(nil, config.Node{Children: cfg})
 	globals.String("state_dir", false, false, DefaultStateDirectory, &config.StateDirectory)
 	globals.String("runtime_dir", false, false, DefaultRuntimeDirectory, &config.RuntimeDirectory)
-	globals.String("prometheus_endpoint", false, false, "", &prometheusEndpoint)
 	globals.String("hostname", false, false, "", nil)
 	globals.String("autogenerated_msg_domain", false, false, "", nil)
 	globals.Custom("tls", false, false, nil, tls.TLSDirective, nil)
@@ -324,13 +301,6 @@ func moduleMain(cfg []config.Node) error {
 		return err
 	}
 
-	// Set by ReadGlobals.
-	if prometheusEndpoint != "" {
-		if err := startPrometheusHTTP(prometheusEndpoint); err != nil {
-			return err
-		}
-	}
-
 	if err := InitDirs(); err != nil {
 		return err
 	}