Merge pull request prometheus-community#618 from sysadmind/multi-target

Add multi-target support

Author: SuperQ

README.md

@@ -21,6 +21,36 @@ docker run \
   quay.io/prometheuscommunity/postgres-exporter
 ```
 
+## Multi-Target Support (BETA)
+**This Feature is in beta and may require changes in future releases. Feedback is welcome.**
+
+This exporter supports the [multi-target pattern](https://prometheus.io/docs/guides/multi-target-exporter/). This allows running a single instance of this exporter for multiple postgres targets. Using the milti-target funcationality of this exporter is **optional** and meant for users where it is impossible to install the exporter as a sidecar. For example SaaS-managed services.
+
+To use the multi-target functionality, send an http request to the endpoint `/probe?target=foo:5432` where target is set to the DSN of the postgres instance to scrape metrics from.
+
+To avoid putting sensitive information like username and password in the URL, preconfigured auth modules are supported via the [auth_modules](#auth_modules) section of the config file. auth_modules for DSNs can be used with the `/probe` endpoint by specifying the `?auth_module=foo` http parameter.
+
+## Configuration File
+
+The configuration file controls the behavior of the exporter. It can be set using the `--config.file` command line flag and defaults to `postgres_exporter.yml`.
+
+### auth_modules
+This section defines preset authentication and connection parameters for use in the [multi-target endpoint](#multi-target-support-beta). `auth_modules` is a map of modules with the key being the identifier which can be used in the `/probe` endpoint.
+Currently only the `userpass` type is supported.
+
+Example:
+```yaml
+auth_modules:
+  foo1: # Set this to any name you want
+    type: userpass
+    userpass:
+      username: first
+      password: firstpass
+    options:
+      # options become key=value parameters of the DSN
+      sslmode: disable
+```
+
 ## Building and running
 
     git clone https://github.com/prometheus-community/postgres_exporter.git

cmd/postgres_exporter/datasource.go

@@ -162,6 +162,12 @@ func getDataSources() ([]string, error) {
 		uri = os.Getenv("DATA_SOURCE_URI")
 	}
 
+	// No datasources found. This allows us to support the multi-target pattern
+	// withouth an explicit datasource.
+	if uri == "" {
+		return []string{}, nil
+	}
+
 	dsn = "postgresql://" + ui + "@" + uri
 
 	return []string{dsn}, nil

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", "Postgres exporter configuration file.").Default("postgres_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()
@@ -85,14 +91,14 @@ func main() {
 		return
 	}
 
-	dsn, err := getDataSources()
-	if err != nil {
-		level.Error(logger).Log("msg", "Failed reading data sources", "err", err.Error())
-		os.Exit(1)
+	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)
 	}
 
-	if len(dsn) == 0 {
-		level.Error(logger).Log("msg", "Couldn't find environment variables describing the datasource to use")
+	dsns, err := getDataSources()
+	if err != nil {
+		level.Error(logger).Log("msg", "Failed reading data sources", "err", err.Error())
 		os.Exit(1)
 	}
 
@@ -106,7 +112,7 @@ func main() {
 		IncludeDatabases(*includeDatabases),
 	}
 
-	exporter := NewExporter(dsn, opts...)
+	exporter := NewExporter(dsns, opts...)
 	defer func() {
 		exporter.servers.Close()
 	}()
@@ -115,23 +121,31 @@ func main() {
 
 	prometheus.MustRegister(exporter)
 
+	// TODO(@sysadmind): Remove this with multi-target support. We are removing multiple DSN support
+	dsn := ""
+	if len(dsns) > 0 {
+		dsn = dsns[0]
+	}
+
 	pe, err := collector.NewPostgresCollector(
 		logger,
 		dsn,
 		[]string{},
 	)
 	if err != nil {
 		level.Error(logger).Log("msg", "Failed to create PostgresCollector", "err", err.Error())
-		os.Exit(1)
+	} else {
+		prometheus.MustRegister(pe)
 	}
-	prometheus.MustRegister(pe)
 
 	http.Handle(*metricPath, promhttp.Handler())
 	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Content-Type", "text/html; charset=UTF-8") // nolint: errcheck
 		w.Write(landingPage)                                       // nolint: errcheck
 	})
 
+	http.HandleFunc("/probe", handleProbe(logger))
+
 	level.Info(logger).Log("msg", "Listening on address", "address", *listenAddress)
 	srv := &http.Server{Addr: *listenAddress}
 	if err := web.ListenAndServe(srv, *webConfig, logger); err != nil {

cmd/postgres_exporter/probe.go

@@ -0,0 +1,105 @@
+// 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 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"
+)
+
+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(@sysadmind): Timeout
+
+		probeSuccessGauge := prometheus.NewGauge(prometheus.GaugeOpts{
+			Name: "probe_success",
+			Help: "Displays whether or not the probe was a success",
+		})
+		probeDurationGauge := prometheus.NewGauge(prometheus.GaugeOpts{
+			Name: "probe_duration_seconds",
+			Help: "Returns how long the probe took to complete in seconds",
+		})
+
+		tl := log.With(logger, "target", target)
+
+		start := time.Now()
+		registry := prometheus.NewRegistry()
+		registry.MustRegister(probeSuccessGauge)
+		registry.MustRegister(probeDurationGauge)
+
+		// Run the probe
+		pc, err := collector.NewProbeCollector(tl, registry, dsn)
+		if err != nil {
+			probeSuccessGauge.Set(0)
+			probeDurationGauge.Set(time.Since(start).Seconds())
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+
+		// TODO(@sysadmind): Remove the registry.MustRegister() call below and instead handle the collection here. That will allow
+		// for the passing of context, handling of timeouts, and more control over the collection.
+		// The current NewProbeCollector() implementation relies on the MustNewConstMetric() call to create the metrics which is not
+		// ideal to use without the registry.MustRegister() call.
+		_ = ctx
+
+		registry.MustRegister(pc)
+
+		duration := time.Since(start).Seconds()
+		probeDurationGauge.Set(duration)
+
+		// TODO check success, etc
+		h := promhttp.HandlerFor(registry, promhttp.HandlerOpts{})
+		h.ServeHTTP(w, r)
+	}
+}

collector/collector.go

@@ -15,6 +15,7 @@ package collector
 
 import (
 	"context"
+	"database/sql"
 	"errors"
 	"fmt"
 	"sync"
@@ -58,7 +59,7 @@ var (
 )
 
 type Collector interface {
-	Update(ctx context.Context, server *server, ch chan<- prometheus.Metric) error
+	Update(ctx context.Context, db *sql.DB, ch chan<- prometheus.Metric) error
 }
 
 func registerCollector(name string, isDefaultEnabled bool, createFunc func(logger log.Logger) (Collector, error)) {
@@ -86,13 +87,13 @@ type PostgresCollector struct {
 	Collectors map[string]Collector
 	logger     log.Logger
 
-	servers map[string]*server
+	db *sql.DB
 }
 
 type Option func(*PostgresCollector) error
 
 // NewPostgresCollector creates a new PostgresCollector.
-func NewPostgresCollector(logger log.Logger, dsns []string, filters []string, options ...Option) (*PostgresCollector, error) {
+func NewPostgresCollector(logger log.Logger, dsn string, filters []string, options ...Option) (*PostgresCollector, error) {
 	p := &PostgresCollector{
 		logger: logger,
 	}
@@ -136,17 +137,18 @@ func NewPostgresCollector(logger log.Logger, dsns []string, filters []string, op
 
 	p.Collectors = collectors
 
-	servers := make(map[string]*server)
-	for _, dsn := range dsns {
-		s, err := makeServer(dsn)
-		if err != nil {
-			return nil, err
-		}
+	if dsn == "" {
+		return nil, errors.New("empty dsn")
+	}
 
-		servers[dsn] = s
+	db, err := sql.Open("postgres", dsn)
+	if err != nil {
+		return nil, err
 	}
+	db.SetMaxOpenConns(1)
+	db.SetMaxIdleConns(1)
 
-	p.servers = servers
+	p.db = db
 
 	return p, nil
 }
@@ -160,32 +162,20 @@ func (p PostgresCollector) Describe(ch chan<- *prometheus.Desc) {
 // Collect implements the prometheus.Collector interface.
 func (p PostgresCollector) Collect(ch chan<- prometheus.Metric) {
 	ctx := context.TODO()
-	wg := sync.WaitGroup{}
-	wg.Add(len(p.servers))
-	for _, s := range p.servers {
-		go func(s *server) {
-			p.subCollect(ctx, s, ch)
-			wg.Done()
-		}(s)
-	}
-	wg.Wait()
-}
-
-func (p PostgresCollector) subCollect(ctx context.Context, server *server, ch chan<- prometheus.Metric) {
 	wg := sync.WaitGroup{}
 	wg.Add(len(p.Collectors))
 	for name, c := range p.Collectors {
 		go func(name string, c Collector) {
-			execute(ctx, name, c, server, ch, p.logger)
+			execute(ctx, name, c, p.db, ch, p.logger)
 			wg.Done()
 		}(name, c)
 	}
 	wg.Wait()
 }
 
-func execute(ctx context.Context, name string, c Collector, s *server, ch chan<- prometheus.Metric, logger log.Logger) {
+func execute(ctx context.Context, name string, c Collector, db *sql.DB, ch chan<- prometheus.Metric, logger log.Logger) {
 	begin := time.Now()
-	err := c.Update(ctx, s, ch)
+	err := c.Update(ctx, db, ch)
 	duration := time.Since(begin)
 	var success float64
 

collector/pg_database.go

@@ -15,6 +15,7 @@ package collector
 
 import (
 	"context"
+	"database/sql"
 
 	"github.com/go-kit/log"
 	"github.com/prometheus/client_golang/prometheus"
@@ -36,15 +37,11 @@ var pgDatabase = map[string]*prometheus.Desc{
 	"size_bytes": prometheus.NewDesc(
 		"pg_database_size_bytes",
 		"Disk space used by the database",
-		[]string{"datname", "server"}, nil,
+		[]string{"datname"}, nil,
 	),
 }
 
-func (PGDatabaseCollector) Update(ctx context.Context, server *server, ch chan<- prometheus.Metric) error {
-	db, err := server.GetDB()
-	if err != nil {
-		return err
-	}
+func (PGDatabaseCollector) Update(ctx context.Context, db *sql.DB, ch chan<- prometheus.Metric) error {
 	rows, err := db.QueryContext(ctx,
 		`SELECT pg_database.datname
 		,pg_database_size(pg_database.datname)
@@ -63,7 +60,7 @@ func (PGDatabaseCollector) Update(ctx context.Context, server *server, ch chan<-
 
 		ch <- prometheus.MustNewConstMetric(
 			pgDatabase["size_bytes"],
-			prometheus.GaugeValue, float64(size), datname, server.GetName(),
+			prometheus.GaugeValue, float64(size), datname,
 		)
 	}
 	if err := rows.Err(); err != nil {