Add config module

The config module supports adding configuration to the exporter via a config file. This supports adding authentication details in a config file so that /probe requests can specify authentication for endpoints

Signed-off-by: Joe Adams <github@joeadams.io>

cmd/postgres_exporter/main.go

@@ -20,6 +20,7 @@ import (
 	"github.com/go-kit/log"
 	"github.com/go-kit/log/level"
 	"github.com/prometheus-community/postgres_exporter/collector"
+	"github.com/prometheus-community/postgres_exporter/config"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"github.com/prometheus/common/promlog"
@@ -31,6 +32,11 @@ import (
 )
 
 var (
+	c = config.ConfigHandler{
+		Config: &config.Config{},
+	}
+
+	configFile             = kingpin.Flag("config.file", "Promehteus exporter configuration file.").Default("postres_exporter.yml").String()
 	listenAddress          = kingpin.Flag("web.listen-address", "Address to listen on for web interface and telemetry.").Default(":9187").Envar("PG_EXPORTER_WEB_LISTEN_ADDRESS").String()
 	webConfig              = webflag.AddFlags(kingpin.CommandLine)
 	metricPath             = kingpin.Flag("web.telemetry-path", "Path under which to expose metrics.").Default("/metrics").Envar("PG_EXPORTER_WEB_TELEMETRY_PATH").String()
@@ -85,6 +91,11 @@ func main() {
 		return
 	}
 
+	if err := c.ReloadConfig(*configFile, logger); err != nil {
+		// This is not fatal, but it means that auth must be provided for every dsn.
+		level.Error(logger).Log("msg", "Error loading config", "err", err)
+	}
+
 	dsns, err := getDataSources()
 	if err != nil {
 		level.Error(logger).Log("msg", "Failed reading data sources", "err", err.Error())

cmd/postgres_exporter/probe.go

@@ -14,11 +14,14 @@
 package main
 
 import (
+	"fmt"
 	"net/http"
 	"time"
 
 	"github.com/go-kit/log"
+	"github.com/go-kit/log/level"
 	"github.com/prometheus-community/postgres_exporter/collector"
+	"github.com/prometheus-community/postgres_exporter/config"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 )
@@ -26,15 +29,38 @@ import (
 func handleProbe(logger log.Logger) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		ctx := r.Context()
+		conf := c.GetConfig()
 		params := r.URL.Query()
 		target := params.Get("target")
 		if target == "" {
 			http.Error(w, "target is required", http.StatusBadRequest)
 			return
 		}
+		var authModule config.AuthModule
+		authModuleName := params.Get("auth_module")
+		if authModuleName == "" {
+			level.Info(logger).Log("msg", "no auth_module specified, using default")
+		} else {
+			var ok bool
+			authModule, ok = conf.AuthModules[authModuleName]
+			if !ok {
+				http.Error(w, fmt.Sprintf("auth_module %s not found", authModuleName), http.StatusBadRequest)
+				return
+			}
+			if authModule.UserPass.Username == "" || authModule.UserPass.Password == "" {
+				http.Error(w, fmt.Sprintf("auth_module %s has no username or password", authModuleName), http.StatusBadRequest)
+				return
+			}
+		}
+
+		dsn, err := authModule.ConfigureTarget(target)
+		if err != nil {
+			level.Error(logger).Log("msg", "failed to configure target", "err", err)
+			http.Error(w, fmt.Sprintf("could not configure dsn for target: %v", err), http.StatusBadRequest)
+			return
+		}
 
 		// TODO: Timeout
-		// TODO: Auth Module
 
 		probeSuccessGauge := prometheus.NewGauge(prometheus.GaugeOpts{
 			Name: "probe_success",
@@ -46,18 +72,14 @@ func handleProbe(logger log.Logger) http.HandlerFunc {
 		})
 
 		tl := log.With(logger, "target", target)
-		_ = tl
 
 		start := time.Now()
 		registry := prometheus.NewRegistry()
 		registry.MustRegister(probeSuccessGauge)
 		registry.MustRegister(probeDurationGauge)
 
-		// TODO(@sysadmind): this is a temp hack until we have a proper auth module
-		target = "postgres://postgres:test@localhost:5432/circle_test?sslmode=disable"
-
 		// Run the probe
-		pc, err := collector.NewProbeCollector(tl, registry, target)
+		pc, err := collector.NewProbeCollector(tl, registry, dsn)
 		if err != nil {
 			probeSuccessGauge.Set(0)
 			probeDurationGauge.Set(time.Since(start).Seconds())

config/config.go

@@ -0,0 +1,126 @@
+// Copyright 2022 The Prometheus 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 config
+
+import (
+	"fmt"
+	"net/url"
+	"os"
+	"strings"
+	"sync"
+
+	"github.com/go-kit/log"
+	"github.com/prometheus/client_golang/prometheus"
+	"gopkg.in/yaml.v3"
+)
+
+var (
+	configReloadSuccess = prometheus.NewGauge(prometheus.GaugeOpts{
+		Namespace: "postgres_exporter",
+		Name:      "config_last_reload_successful",
+		Help:      "Postgres exporter config loaded successfully.",
+	})
+
+	configReloadSeconds = prometheus.NewGauge(prometheus.GaugeOpts{
+		Namespace: "postgres_exporter",
+		Name:      "config_last_reload_success_timestamp_seconds",
+		Help:      "Timestamp of the last successful configuration reload.",
+	})
+)
+
+func init() {
+	prometheus.MustRegister(configReloadSuccess)
+	prometheus.MustRegister(configReloadSeconds)
+}
+
+type Config struct {
+	AuthModules map[string]AuthModule `yaml:"auth_modules"`
+}
+
+type AuthModule struct {
+	Type     string   `yaml:"type"`
+	UserPass UserPass `yaml:"userpass,omitempty"`
+	// Add alternative auth modules here
+	Options map[string]string `yaml:"options"`
+}
+
+type UserPass struct {
+	Username string `yaml:"username"`
+	Password string `yaml:"password"`
+}
+
+type ConfigHandler struct {
+	sync.RWMutex
+	Config *Config
+}
+
+func (ch *ConfigHandler) GetConfig() *Config {
+	ch.RLock()
+	defer ch.RUnlock()
+	return ch.Config
+}
+
+func (ch *ConfigHandler) ReloadConfig(f string, logger log.Logger) error {
+	config := &Config{}
+	var err error
+	defer func() {
+		if err != nil {
+			configReloadSuccess.Set(0)
+		} else {
+			configReloadSuccess.Set(1)
+			configReloadSeconds.SetToCurrentTime()
+		}
+	}()
+
+	yamlReader, err := os.Open(f)
+	if err != nil {
+		return fmt.Errorf("Error opening config file %q: %s", f, err)
+	}
+	defer yamlReader.Close()
+	decoder := yaml.NewDecoder(yamlReader)
+	decoder.KnownFields(true)
+
+	if err = decoder.Decode(config); err != nil {
+		return fmt.Errorf("Error parsing config file %q: %s", f, err)
+	}
+
+	ch.Lock()
+	ch.Config = config
+	ch.Unlock()
+	return nil
+}
+
+func (m AuthModule) ConfigureTarget(target string) (string, error) {
+	// ip:port urls do not parse properly and that is the typical way users interact with postgres
+	t := fmt.Sprintf("exporter://%s", target)
+	u, err := url.Parse(t)
+	if err != nil {
+		return "", err
+	}
+
+	if m.Type == "userpass" {
+		u.User = url.UserPassword(m.UserPass.Username, m.UserPass.Password)
+	}
+
+	query := u.Query()
+	for k, v := range m.Options {
+		query.Set(k, v)
+	}
+	u.RawQuery = query.Encode()
+
+	parsed := u.String()
+	trim := strings.TrimPrefix(parsed, "exporter://")
+
+	return trim, nil
+}

config/config_test.go

@@ -0,0 +1,58 @@
+// Copyright 2022 The Prometheus 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 config
+
+import (
+	"testing"
+)
+
+func TestLoadConfig(t *testing.T) {
+	ch := &ConfigHandler{
+		Config: &Config{},
+	}
+
+	err := ch.ReloadConfig("testdata/config-good.yaml", nil)
+	if err != nil {
+		t.Errorf("Error loading config: %s", err)
+	}
+}
+
+func TestLoadBadConfigs(t *testing.T) {
+	ch := &ConfigHandler{
+		Config: &Config{},
+	}
+
+	tests := []struct {
+		input string
+		want  string
+	}{
+		{
+			input: "testdata/config-bad-auth-module.yaml",
+			want:  "Error parsing config file \"testdata/config-bad-auth-module.yaml\": yaml: unmarshal errors:\n  line 3: field pretendauth not found in type config.AuthModule",
+		},
+		{
+			input: "testdata/config-bad-extra-field.yaml",
+			want:  "Error parsing config file \"testdata/config-bad-extra-field.yaml\": yaml: unmarshal errors:\n  line 8: field doesNotExist not found in type config.AuthModule",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.input, func(t *testing.T) {
+			got := ch.ReloadConfig(test.input, nil)
+			if got == nil || got.Error() != test.want {
+				t.Fatalf("ReloadConfig(%q) = %v, want %s", test.input, got, test.want)
+			}
+		})
+	}
+}

config/testdata/config-bad-auth-module.yaml

@@ -0,0 +1,7 @@
+auth_modules:
+  foo:
+    pretendauth:
+      username: test
+      password: pass
+    options:
+      extra: "1"

config/testdata/config-bad-extra-field.yaml

@@ -0,0 +1,8 @@
+auth_modules:
+  foo:
+    userpass:
+      username: test
+      password: pass
+    options:
+      extra: "1"
+    doesNotExist: test

config/testdata/config-good.yaml

@@ -0,0 +1,8 @@
+auth_modules:
+  first:
+    type: userpass
+    userpass:
+      username: first
+      password: firstpass
+    options:
+      sslmode: disable

go.mod

@@ -13,6 +13,7 @@ require (
 	gopkg.in/alecthomas/kingpin.v2 v2.2.6
 	gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c
 	gopkg.in/yaml.v2 v2.4.0
+	gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b
 )
 
 require (

go.sum

@@ -494,6 +494,8 @@ gopkg.in/yaml.v2 v2.2.5/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.3.0/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.4.0 h1:D8xgwECY7CYvx+Y2n4sBz93Jn9JRvxdiyyo8CTfuKaY=
 gopkg.in/yaml.v2 v2.4.0/go.mod h1:RDklbk79AGWmwhnvt/jBztapEOGDOx6ZbXqjP6csGnQ=
+gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b h1:h8qDotaEPuJATrMmW04NCwg7v22aHH28wwpauUhK9Oo=
+gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 honnef.co/go/tools v0.0.0-20190102054323-c2f93a96b099/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
 honnef.co/go/tools v0.0.0-20190106161140-3f1c8253044a/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
 honnef.co/go/tools v0.0.0-20190418001031-e561f6794a2a/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=