From e02fe4f36c1b18a57fcfe27026cbf84ed0c78611 Mon Sep 17 00:00:00 2001
From: adnull <d.lexand@gmail.com>
Date: Tue, 10 Oct 2023 23:40:41 +0300
Subject: [PATCH] Multi target support (#653)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* added multi target feature

* added connect timeout opts

* added tests

* fixed test

* fixed dockerfile

* Bump github.com/golangci/golangci-lint from 1.47.3 to 1.52.2 in /tools (#639)

Bumps [github.com/golangci/golangci-lint](https://github.com/golangci/golangci-lint) from 1.47.3 to 1.52.2.
- [Release notes](https://github.com/golangci/golangci-lint/releases)
- [Changelog](https://github.com/golangci/golangci-lint/blob/master/CHANGELOG.md)
- [Commits](https://github.com/golangci/golangci-lint/compare/v1.47.3...v1.52.2)

---
updated-dependencies:
- dependency-name: github.com/golangci/golangci-lint
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

* Bump github.com/golangci/golangci-lint from 1.52.2 to 1.53.2 in /tools (#665)

Bumps [github.com/golangci/golangci-lint](https://github.com/golangci/golangci-lint) from 1.52.2 to 1.53.2.
- [Release notes](https://github.com/golangci/golangci-lint/releases)
- [Changelog](https://github.com/golangci/golangci-lint/blob/master/CHANGELOG.md)
- [Commits](https://github.com/golangci/golangci-lint/compare/v1.52.2...v1.53.2)

---
updated-dependencies:
- dependency-name: github.com/golangci/golangci-lint
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

* Remove `prometheus/client_golang` replace (#682)

* Remove prometheus/client_golang replace

* Apply formater

* Downgrade client_golang to previous version

* Upgrade exporter-toolkit to v0.10.0

* added multi target feature

* added connect timeout opts

* fixed connect

* formatted code

* fixed linter warnings

* Update README.md

* Update README.md

* updated license

* Update exporter/server.go

Co-authored-by: Nurlan Moldomurov <nurlan.moldomurov@percona.com>

* fixed according to review

* formatted the code

* minor changes according to the linters

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Marc Tudurí <marctc@protonmail.com>
Co-authored-by: Jiří Čtvrtka <62988319+JiriCtvrtka@users.noreply.github.com>
Co-authored-by: Nurlan Moldomurov <nurlan.moldomurov@percona.com>
Co-authored-by: Nurlan Moldomurov <bupychuk1989@gmail.com>
---
 Dockerfile                    |  15 ++++-
 README.md                     |  11 ++++
 exporter/base_collector.go    |   5 +-
 exporter/exporter.go          |  72 ++++++----------------
 exporter/exporter_test.go     |  80 ++++++++++++++++++++----
 exporter/multi_target_test.go |  72 ++++++++++++++++++++++
 exporter/server.go            | 111 ++++++++++++++++++++++++++++++++++
 internal/tu/testutils.go      |   2 +
 main.go                       | 108 +++++++++++++++++++++------------
 main_test.go                  |   6 +-
 10 files changed, 371 insertions(+), 111 deletions(-)
 create mode 100644 exporter/multi_target_test.go
 create mode 100644 exporter/server.go

diff --git a/Dockerfile b/Dockerfile
index 3ed6f8ffb..759ab614a 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,9 +1,18 @@
 FROM alpine AS builder
 RUN apk add --no-cache ca-certificates
 
-FROM scratch AS final
+FROM golang:alpine as builder2
+
+RUN apk update && apk add make
+RUN mkdir /source
+COPY . /source
+WORKDIR /source
+RUN make init
+RUN make build
+
+FROM alpine AS final
 USER 65535:65535
-COPY  --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
-COPY ./mongodb_exporter /
+COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
+COPY --from=builder2 /source/mongodb_exporter /
 EXPOSE 9216
 ENTRYPOINT ["/mongodb_exporter"]
\ No newline at end of file
diff --git a/README.md b/README.md
index f20cefb7a..6fbd05511 100644
--- a/README.md
+++ b/README.md
@@ -86,6 +86,17 @@ export MONGODB_PASSWORD=YYY
 mongodb_exporter_linux_amd64/mongodb_exporter --mongodb.uri=mongodb://127.0.0.1:17001 --mongodb.collstats-colls=db1.c1,db2.c2
 ```
 
+#### Multi-target support
+You can run the exporter specifying multiple URIs, devided by a comma in --mongodb.uri option or MONGODB_URI environment variable in order to monitor multiple mongodb instances with the a single mongodb_exporter instance.
+```sh
+--mongodb.uri=mongodb://user:pass@127.0.0.1:27017/admin,mongodb://user2:pass2@127.0.0.1:27018/admin
+```
+In this case you can use the **/scrape** endpoint with the **target** parameter to retreive the specified tartget's metrics.  When querying the data you can use just mongodb://host:port in the targer parameter without other parameters and, of course without host credentials
+```sh
+GET /scrape?target=mongodb://127.0.0.1:27018
+```
+
+
 #### Enabling collstats metrics gathering
 `--mongodb.collstats-colls` receives a list of databases and collections to monitor using collstats.
 Usage example: `--mongodb.collstats-colls=database1.collection1,database2.collection2`
diff --git a/exporter/base_collector.go b/exporter/base_collector.go
index c16dc34d5..4184112d2 100644
--- a/exporter/base_collector.go
+++ b/exporter/base_collector.go
@@ -43,7 +43,10 @@ func newBaseCollector(client *mongo.Client, logger *logrus.Logger) *baseCollecto
 func (d *baseCollector) Describe(ctx context.Context, ch chan<- *prometheus.Desc, collect func(mCh chan<- prometheus.Metric)) {
 	select {
 	case <-ctx.Done():
-		return
+		// don't interrupt, let mongodb_up metric to be registered if on timeout we still don't have client connected
+		if d.client != nil {
+			return
+		}
 	default:
 	}
 
diff --git a/exporter/exporter.go b/exporter/exporter.go
index 4787abe7a..ce11f0667 100644
--- a/exporter/exporter.go
+++ b/exporter/exporter.go
@@ -21,15 +21,12 @@ import (
 	"fmt"
 	"net/http"
 	_ "net/http/pprof"
-	"os"
 	"strconv"
 	"sync"
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
-	"github.com/prometheus/common/promlog"
-	"github.com/prometheus/exporter-toolkit/web"
 	"github.com/sirupsen/logrus"
 	"go.mongodb.org/mongo-driver/mongo"
 
@@ -38,12 +35,10 @@ import (
 
 // Exporter holds Exporter methods and attributes.
 type Exporter struct {
-	path                  string
 	client                *mongo.Client
 	clientMu              sync.Mutex
 	logger                *logrus.Logger
 	opts                  *Opts
-	webListenAddress      string
 	lock                  *sync.Mutex
 	totalCollectionsCount int
 }
@@ -56,6 +51,7 @@ type Opts struct {
 	CollStatsLimit         int
 	CompatibleMode         bool
 	DirectConnect          bool
+	ConnectTimeoutMS       int
 	DisableDefaultRegistry bool
 	DiscoveringMode        bool
 	GlobalConnPool         bool
@@ -76,10 +72,8 @@ type Opts struct {
 
 	IndexStatsCollections []string
 	Logger                *logrus.Logger
-	Path                  string
-	URI                   string
-	WebListenAddress      string
-	TLSConfigPath         string
+
+	URI string
 }
 
 var (
@@ -103,16 +97,9 @@ func New(opts *Opts) *Exporter {
 
 	ctx := context.Background()
 
-	if opts.Path == "" {
-		opts.Logger.Warn("Web telemetry path \"\" invalid, falling back to \"/\" instead")
-		opts.Path = "/"
-	}
-
 	exp := &Exporter{
-		path:                  opts.Path,
 		logger:                opts.Logger,
 		opts:                  opts,
-		webListenAddress:      opts.WebListenAddress,
 		lock:                  &sync.Mutex{},
 		totalCollectionsCount: -1, // Not calculated yet. waiting the db connection.
 	}
@@ -257,7 +244,7 @@ func (e *Exporter) getClient(ctx context.Context) (*mongo.Client, error) {
 			return e.client, nil
 		}
 
-		client, err := connect(context.Background(), e.opts.URI, e.opts.DirectConnect)
+		client, err := connect(context.Background(), e.opts)
 		if err != nil {
 			return nil, err
 		}
@@ -267,7 +254,7 @@ func (e *Exporter) getClient(ctx context.Context) (*mongo.Client, error) {
 	}
 
 	// !e.opts.GlobalConnPool: create new client for every scrape.
-	client, err := connect(ctx, e.opts.URI, e.opts.DirectConnect)
+	client, err := connect(ctx, e.opts)
 	if err != nil {
 		return nil, err
 	}
@@ -350,14 +337,15 @@ func (e *Exporter) Handler() http.Handler {
 			gatherers = append(gatherers, prometheus.DefaultGatherer)
 		}
 
+		var ti *topologyInfo
 		if client != nil {
 			// Topology can change between requests, so we need to get it every time.
-			ti := newTopologyInfo(ctx, client, e.logger)
-
-			registry := e.makeRegistry(ctx, client, ti, requestOpts)
-			gatherers = append(gatherers, registry)
+			ti = newTopologyInfo(ctx, client, e.logger)
 		}
 
+		registry := e.makeRegistry(ctx, client, ti, requestOpts)
+		gatherers = append(gatherers, registry)
+
 		// Delegate http serving to Prometheus client library, which will call collector.Collect.
 		h := promhttp.HandlerFor(gatherers, promhttp.HandlerOpts{
 			ErrorHandling: promhttp.ContinueOnError,
@@ -368,41 +356,21 @@ func (e *Exporter) Handler() http.Handler {
 	})
 }
 
-// Run starts the exporter.
-func (e *Exporter) Run() {
-	mux := http.DefaultServeMux
-	mux.Handle(e.path, e.Handler())
-	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
-		w.Write([]byte(`<html>
-            <head><title>MongoDB Exporter</title></head>
-            <body>
-            <h1>MongoDB Exporter</h1>
-            <p><a href='/metrics'>Metrics</a></p>
-            </body>
-            </html>`))
-	})
-
-	server := &http.Server{
-		Handler: mux,
-	}
-	flags := &web.FlagConfig{
-		WebListenAddresses: &[]string{e.webListenAddress},
-		WebConfigFile:      &e.opts.TLSConfigPath,
-	}
-	if err := web.ListenAndServe(server, flags, promlog.New(&promlog.Config{})); err != nil {
-		e.logger.Errorf("error starting server: %v", err)
-		os.Exit(1)
-	}
-}
-
-func connect(ctx context.Context, dsn string, directConnect bool) (*mongo.Client, error) {
-	clientOpts, err := dsn_fix.ClientOptionsForDSN(dsn)
+func connect(ctx context.Context, opts *Opts) (*mongo.Client, error) {
+	clientOpts, err := dsn_fix.ClientOptionsForDSN(opts.URI)
 	if err != nil {
 		return nil, fmt.Errorf("invalid dsn: %w", err)
 	}
-	clientOpts.SetDirect(directConnect)
+
+	clientOpts.SetDirect(opts.DirectConnect)
 	clientOpts.SetAppName("mongodb_exporter")
 
+	if clientOpts.ConnectTimeout == nil {
+		connectTimeout := time.Duration(opts.ConnectTimeoutMS) * time.Millisecond
+		clientOpts.SetConnectTimeout(connectTimeout)
+		clientOpts.SetServerSelectionTimeout(connectTimeout)
+	}
+
 	client, err := mongo.Connect(ctx, clientOpts)
 	if err != nil {
 		return nil, fmt.Errorf("invalid MongoDB options: %w", err)
diff --git a/exporter/exporter_test.go b/exporter/exporter_test.go
index b340c8810..9dba21159 100644
--- a/exporter/exporter_test.go
+++ b/exporter/exporter_test.go
@@ -19,11 +19,15 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"net"
 	"net/http"
 	"net/http/httptest"
+	"strconv"
+	"strings"
 	"sync"
 	"testing"
 
+	"github.com/prometheus/client_golang/prometheus/testutil"
 	"github.com/sirupsen/logrus"
 	"github.com/stretchr/testify/assert"
 
@@ -61,8 +65,11 @@ func TestConnect(t *testing.T) {
 
 	t.Run("Connect without SSL", func(t *testing.T) {
 		for name, port := range ports {
-			dsn := fmt.Sprintf("mongodb://%s:%s/admin", hostname, port)
-			client, err := connect(ctx, dsn, true)
+			exporterOpts := &Opts{
+				URI:           fmt.Sprintf("mongodb://%s/admin", net.JoinHostPort(hostname, port)),
+				DirectConnect: true,
+			}
+			client, err := connect(ctx, exporterOpts)
 			assert.NoError(t, err, name)
 			err = client.Disconnect(ctx)
 			assert.NoError(t, err, name)
@@ -167,17 +174,17 @@ func TestMongoS(t *testing.T) {
 	}
 
 	for _, test := range tests {
-		dsn := fmt.Sprintf("mongodb://%s:%s/admin", hostname, test.port)
-		client, err := connect(ctx, dsn, true)
-		assert.NoError(t, err)
-
 		exporterOpts := &Opts{
 			Logger:                 logrus.New(),
-			URI:                    dsn,
+			URI:                    fmt.Sprintf("mongodb://%s/admin", net.JoinHostPort(hostname, test.port)),
+			DirectConnect:          true,
 			GlobalConnPool:         false,
 			EnableReplicasetStatus: true,
 		}
 
+		client, err := connect(ctx, exporterOpts)
+		assert.NoError(t, err)
+
 		e := New(exporterOpts)
 
 		rsgsc := newReplicationSetStatusCollector(ctx, client, e.opts.Logger,
@@ -195,17 +202,17 @@ func TestMongoS(t *testing.T) {
 func TestMongoUp(t *testing.T) {
 	ctx := context.Background()
 
-	dsn := "mongodb://127.0.0.1:123456/admin"
-	client, err := connect(ctx, dsn, true)
-	assert.Error(t, err)
-
 	exporterOpts := &Opts{
 		Logger:         logrus.New(),
-		URI:            dsn,
+		URI:            "mongodb://127.0.0.1:123456/admin",
+		DirectConnect:  true,
 		GlobalConnPool: false,
 		CollectAll:     true,
 	}
 
+	client, err := connect(ctx, exporterOpts)
+	assert.Error(t, err)
+
 	e := New(exporterOpts)
 
 	gc := newGeneralCollector(ctx, client, e.opts.Logger)
@@ -215,3 +222,52 @@ func TestMongoUp(t *testing.T) {
 	res := r.Unregister(gc)
 	assert.Equal(t, true, res)
 }
+
+func TestMongoUpMetric(t *testing.T) {
+	ctx := context.Background()
+
+	type testcase struct {
+		URI  string
+		Want int
+	}
+
+	testCases := []testcase{
+		{URI: "mongodb://127.0.0.1:12345/admin", Want: 0},
+		{URI: fmt.Sprintf("mongodb://127.0.0.1:%s/admin", tu.GetenvDefault("TEST_MONGODB_STANDALONE_PORT", "27017")), Want: 1},
+	}
+
+	for _, tc := range testCases {
+		exporterOpts := &Opts{
+			Logger:           logrus.New(),
+			URI:              tc.URI,
+			ConnectTimeoutMS: 200,
+			DirectConnect:    true,
+			GlobalConnPool:   false,
+			CollectAll:       true,
+		}
+
+		client, err := connect(ctx, exporterOpts)
+		if tc.Want == 1 {
+			assert.NoError(t, err, "Must be able to connect to %s", tc.URI)
+		} else {
+			assert.Error(t, err, "Must be unable to connect to %s", tc.URI)
+		}
+
+		e := New(exporterOpts)
+		gc := newGeneralCollector(ctx, client, e.opts.Logger)
+		r := e.makeRegistry(ctx, client, new(labelsGetterMock), *e.opts)
+
+		expected := strings.NewReader(`
+		# HELP mongodb_up Whether MongoDB is up.
+		# TYPE mongodb_up gauge
+		mongodb_up ` + strconv.Itoa(tc.Want) + "\n")
+		filter := []string{
+			"mongodb_up",
+		}
+		err = testutil.CollectAndCompare(gc, expected, filter...)
+		assert.NoError(t, err, "mongodb_up metric should be %d", tc.Want)
+
+		res := r.Unregister(gc)
+		assert.Equal(t, true, res)
+	}
+}
diff --git a/exporter/multi_target_test.go b/exporter/multi_target_test.go
new file mode 100644
index 000000000..f689ce7c7
--- /dev/null
+++ b/exporter/multi_target_test.go
@@ -0,0 +1,72 @@
+// mongodb_exporter
+// Copyright (C) 2017 Percona LLC
+//
+// 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 exporter
+
+import (
+	"fmt"
+	"net"
+	"testing"
+
+	"github.com/sirupsen/logrus"
+	"github.com/stretchr/testify/assert"
+
+	"github.com/percona/mongodb_exporter/internal/tu"
+)
+
+func TestMultiTarget(t *testing.T) {
+	hostname := "127.0.0.1"
+	opts := []*Opts{
+		{
+			URI:              fmt.Sprintf("mongodb://%s", net.JoinHostPort(hostname, tu.GetenvDefault("TEST_MONGODB_STANDALONE_PORT", "27017"))),
+			DirectConnect:    true,
+			ConnectTimeoutMS: 1000,
+		},
+		{
+			URI:              fmt.Sprintf("mongodb://%s", net.JoinHostPort(hostname, tu.GetenvDefault("TEST_MONGODB_S1_PRIMARY_PORT", "17001"))),
+			DirectConnect:    true,
+			ConnectTimeoutMS: 1000,
+		},
+		{
+			URI:              fmt.Sprintf("mongodb://%s", net.JoinHostPort(hostname, tu.GetenvDefault("TEST_MONGODB_S2_PRIMARY_PORT", "17004"))),
+			DirectConnect:    true,
+			ConnectTimeoutMS: 1000,
+		},
+		{
+			URI:              fmt.Sprintf("mongodb://%s", net.JoinHostPort(hostname, "12345")),
+			DirectConnect:    true,
+			ConnectTimeoutMS: 1000,
+		},
+	}
+	exporters := make([]*Exporter, len(opts))
+
+	for i, opt := range opts {
+		exporters[i] = New(opt)
+	}
+	log := logrus.New()
+	serverMap := buildServerMap(exporters, log)
+
+	expected := []string{
+		"mongodb_up 1\n",
+		"mongodb_up 1\n",
+		"mongodb_up 1\n",
+		"mongodb_up 0\n",
+	}
+
+	// Test all targets
+	for sn, opt := range opts {
+		assert.HTTPBodyContains(t, multiTargetHandler(serverMap), "GET", fmt.Sprintf("?target=%s", opt.URI), nil, expected[sn])
+	}
+}
diff --git a/exporter/server.go b/exporter/server.go
new file mode 100644
index 000000000..6788acb31
--- /dev/null
+++ b/exporter/server.go
@@ -0,0 +1,111 @@
+// mongodb_exporter
+// Copyright (C) 2017 Percona LLC
+//
+// 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 exporter
+
+import (
+	"net/http"
+	"net/url"
+	"os"
+	"strings"
+	"time"
+
+	"github.com/prometheus/common/promlog"
+	"github.com/prometheus/exporter-toolkit/web"
+	"github.com/sirupsen/logrus"
+)
+
+// ServerMap stores http handlers for each host
+type ServerMap map[string]http.Handler
+
+// ServerOpts is the options for the main http handler
+type ServerOpts struct {
+	Path             string
+	MultiTargetPath  string
+	WebListenAddress string
+	TLSConfigPath    string
+}
+
+// Runs the main web-server
+func RunWebServer(opts *ServerOpts, exporters []*Exporter, log *logrus.Logger) {
+	mux := http.DefaultServeMux
+
+	if len(exporters) == 0 {
+		panic("No exporters were built. You must specify --mongodb.uri command argument or MONGODB_URI environment variable")
+	}
+
+	serverMap := buildServerMap(exporters, log)
+
+	defaultExporter := exporters[0]
+	mux.Handle(opts.Path, defaultExporter.Handler())
+	mux.HandleFunc(opts.MultiTargetPath, multiTargetHandler(serverMap))
+
+	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+		_, err := w.Write([]byte(`<html>
+            <head><title>MongoDB Exporter</title></head>
+            <body>
+            <h1>MongoDB Exporter</h1>
+            <p><a href='/metrics'>Metrics</a></p>
+            </body>
+            </html>`))
+		if err != nil {
+			log.Errorf("error writing response: %v", err)
+		}
+	})
+
+	server := &http.Server{
+		ReadHeaderTimeout: 2 * time.Second,
+		Handler:           mux,
+	}
+	flags := &web.FlagConfig{
+		WebListenAddresses: &[]string{opts.WebListenAddress},
+		WebConfigFile:      &opts.TLSConfigPath,
+	}
+	if err := web.ListenAndServe(server, flags, promlog.New(&promlog.Config{})); err != nil {
+		log.Errorf("error starting server: %v", err)
+		os.Exit(1)
+	}
+}
+
+func multiTargetHandler(serverMap ServerMap) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		targetHost := r.URL.Query().Get("target")
+		if targetHost != "" {
+			if !strings.HasPrefix(targetHost, "mongodb://") {
+				targetHost = "mongodb://" + targetHost
+			}
+			if uri, err := url.Parse(targetHost); err == nil {
+				if e, ok := serverMap[uri.Host]; ok {
+					e.ServeHTTP(w, r)
+					return
+				}
+			}
+		}
+		http.Error(w, "Unable to find target", http.StatusNotFound)
+	}
+}
+
+func buildServerMap(exporters []*Exporter, log *logrus.Logger) ServerMap {
+	servers := make(ServerMap, len(exporters))
+	for _, e := range exporters {
+		if url, err := url.Parse(e.opts.URI); err == nil {
+			servers[url.Host] = e.Handler()
+		} else {
+			log.Errorf("Unable to parse addr %s as url: %s", e.opts.URI, err)
+		}
+	}
+
+	return servers
+}
diff --git a/internal/tu/testutils.go b/internal/tu/testutils.go
index ce138ab3f..a93ccdfe1 100644
--- a/internal/tu/testutils.go
+++ b/internal/tu/testutils.go
@@ -67,6 +67,7 @@ func GetenvDefault(key, defaultValue string) string {
 func DefaultTestClient(ctx context.Context, t *testing.T) *mongo.Client {
 	port, err := PortForContainer("mongo-1-1")
 	require.NoError(t, err)
+
 	return TestClient(ctx, port, t)
 }
 
@@ -103,6 +104,7 @@ func GetImageNameForDefault() (string, string, error) {
 			break
 		}
 	}
+
 	return imageBaseName, version, nil
 }
 
diff --git a/main.go b/main.go
index 1e5d13561..83948ff27 100644
--- a/main.go
+++ b/main.go
@@ -34,17 +34,18 @@ var (
 
 // GlobalFlags has command line flags to configure the exporter.
 type GlobalFlags struct {
-	User                  string `name:"mongodb.user" help:"monitor user, need clusterMonitor role in admin db and read role in local db" env:"MONGODB_USER" placeholder:"monitorUser"`
-	Password              string `name:"mongodb.password" help:"monitor user password" env:"MONGODB_PASSWORD" placeholder:"monitorPassword"`
-	CollStatsNamespaces   string `name:"mongodb.collstats-colls" help:"List of comma separared databases.collections to get $collStats" placeholder:"db1,db2.col2"`
-	IndexStatsCollections string `name:"mongodb.indexstats-colls" help:"List of comma separared databases.collections to get $indexStats" placeholder:"db1.col1,db2.col2"`
-	URI                   string `name:"mongodb.uri" help:"MongoDB connection URI" env:"MONGODB_URI" placeholder:"mongodb://user:pass@127.0.0.1:27017/admin?ssl=true"`
-	GlobalConnPool        bool   `name:"mongodb.global-conn-pool" help:"Use global connection pool instead of creating new pool for each http request." negatable:""`
-	DirectConnect         bool   `name:"mongodb.direct-connect" help:"Whether or not a direct connect should be made. Direct connections are not valid if multiple hosts are specified or an SRV URI is used." default:"true" negatable:""`
-	WebListenAddress      string `name:"web.listen-address" help:"Address to listen on for web interface and telemetry" default:":9216"`
-	WebTelemetryPath      string `name:"web.telemetry-path" help:"Metrics expose path" default:"/metrics"`
-	TLSConfigPath         string `name:"web.config" help:"Path to the file having Prometheus TLS config for basic auth"`
-	LogLevel              string `name:"log.level" help:"Only log messages with the given severity or above. Valid levels: [debug, info, warn, error, fatal]" enum:"debug,info,warn,error,fatal" default:"error"`
+	User                  string   `name:"mongodb.user" help:"monitor user, need clusterMonitor role in admin db and read role in local db" env:"MONGODB_USER" placeholder:"monitorUser"`
+	Password              string   `name:"mongodb.password" help:"monitor user password" env:"MONGODB_PASSWORD" placeholder:"monitorPassword"`
+	CollStatsNamespaces   string   `name:"mongodb.collstats-colls" help:"List of comma separared databases.collections to get $collStats" placeholder:"db1,db2.col2"`
+	IndexStatsCollections string   `name:"mongodb.indexstats-colls" help:"List of comma separared databases.collections to get $indexStats" placeholder:"db1.col1,db2.col2"`
+	URI                   []string `name:"mongodb.uri" help:"MongoDB connection URI" env:"MONGODB_URI" placeholder:"mongodb://user:pass@127.0.0.1:27017/admin?ssl=true"`
+	GlobalConnPool        bool     `name:"mongodb.global-conn-pool" help:"Use global connection pool instead of creating new pool for each http request." negatable:""`
+	DirectConnect         bool     `name:"mongodb.direct-connect" help:"Whether or not a direct connect should be made. Direct connections are not valid if multiple hosts are specified or an SRV URI is used." default:"true" negatable:""`
+	WebListenAddress      string   `name:"web.listen-address" help:"Address to listen on for web interface and telemetry" default:":9216"`
+	WebTelemetryPath      string   `name:"web.telemetry-path" help:"Metrics expose path" default:"/metrics"`
+	TLSConfigPath         string   `name:"web.config" help:"Path to the file having Prometheus TLS config for basic auth"`
+	LogLevel              string   `name:"log.level" help:"Only log messages with the given severity or above. Valid levels: [debug, info, warn, error, fatal]" enum:"debug,info,warn,error,fatal" default:"error"`
+	ConnectTimeoutMS      int      `name:"mongodb.connect-timeout-ms" help:"Connection timeout in milliseconds" default:"5000"`
 
 	EnableDiagnosticData     bool `name:"collector.diagnosticdata" help:"Enable collecting metrics from getDiagnosticData"`
 	EnableReplicasetStatus   bool `name:"collector.replicasetstatus" help:"Enable collecting metrics from replSetGetStatus"`
@@ -71,7 +72,7 @@ type GlobalFlags struct {
 
 func main() {
 	var opts GlobalFlags
-	_ = kong.Parse(&opts,
+	ctx := kong.Parse(&opts,
 		kong.Name("mongodb_exporter"),
 		kong.Description("MongoDB Prometheus exporter"),
 		kong.UsageOnError(),
@@ -87,30 +88,9 @@ func main() {
 		fmt.Printf("Version: %s\n", version)
 		fmt.Printf("Commit: %s\n", commit)
 		fmt.Printf("Build date: %s\n", buildDate)
-
 		return
 	}
 
-	e := buildExporter(opts)
-	e.Run()
-}
-
-func buildURI(uri string, user string, password string) string {
-	// IF user@pass not contained in uri AND custom user and pass supplied in arguments
-	// DO concat a new uri with user and pass arguments value
-	if !strings.Contains(uri, "@") && user != "" && password != "" {
-		// trim mongodb:// prefix to handle user and pass logic
-		uri = strings.TrimPrefix(uri, "mongodb://")
-		// add user and pass to the uri
-		uri = fmt.Sprintf("%s:%s@%s", user, password, uri)
-	}
-	if !strings.HasPrefix(uri, "mongodb") {
-		uri = "mongodb://" + uri
-	}
-	return uri
-}
-
-func buildExporter(opts GlobalFlags) *exporter.Exporter {
 	log := logrus.New()
 
 	levels := map[string]logrus.Level{
@@ -121,12 +101,29 @@ func buildExporter(opts GlobalFlags) *exporter.Exporter {
 		"warn":  logrus.WarnLevel,
 	}
 	log.SetLevel(levels[opts.LogLevel])
-
 	log.Debugf("Compatible mode: %v", opts.CompatibleMode)
 
-	opts.URI = buildURI(opts.URI, opts.User, opts.Password)
+	if opts.WebTelemetryPath == "" {
+		log.Warn("Web telemetry path \"\" invalid, falling back to \"/\" instead")
+		opts.WebTelemetryPath = "/"
+	}
+
+	if len(opts.URI) == 0 {
+		ctx.Fatalf("No MongoDB hosts were specified. You must specify the host(s) with the --mongodb.uri command argument or the MONGODB_URI environment variable")
+	}
+
+	serverOpts := &exporter.ServerOpts{
+		Path:             opts.WebTelemetryPath,
+		MultiTargetPath:  "/scrape",
+		WebListenAddress: opts.WebListenAddress,
+		TLSConfigPath:    opts.TLSConfigPath,
+	}
+	exporter.RunWebServer(serverOpts, buildServers(opts, log), log)
+}
 
-	log.Debugf("Connection URI: %s", opts.URI)
+func buildExporter(opts GlobalFlags, uri string, log *logrus.Logger) *exporter.Exporter {
+	uri = buildURI(uri, opts.User, opts.Password)
+	log.Debugf("Connection URI: %s", uri)
 
 	exporterOpts := &exporter.Opts{
 		CollStatsNamespaces:   strings.Split(opts.CollStatsNamespaces, ","),
@@ -134,12 +131,10 @@ func buildExporter(opts GlobalFlags) *exporter.Exporter {
 		DiscoveringMode:       opts.DiscoveringMode,
 		IndexStatsCollections: strings.Split(opts.IndexStatsCollections, ","),
 		Logger:                log,
-		Path:                  opts.WebTelemetryPath,
-		URI:                   opts.URI,
+		URI:                   uri,
 		GlobalConnPool:        opts.GlobalConnPool,
-		WebListenAddress:      opts.WebListenAddress,
-		TLSConfigPath:         opts.TLSConfigPath,
 		DirectConnect:         opts.DirectConnect,
+		ConnectTimeoutMS:      opts.ConnectTimeoutMS,
 
 		EnableDiagnosticData:     opts.EnableDiagnosticData,
 		EnableReplicasetStatus:   opts.EnableReplicasetStatus,
@@ -162,3 +157,36 @@ func buildExporter(opts GlobalFlags) *exporter.Exporter {
 
 	return e
 }
+
+func buildServers(opts GlobalFlags, log *logrus.Logger) []*exporter.Exporter {
+	servers := make([]*exporter.Exporter, len(opts.URI))
+
+	for serverIdx := range opts.URI {
+		URI := opts.URI[serverIdx]
+
+		if !strings.HasPrefix(URI, "mongodb") {
+			log.Debugf("Prepending mongodb:// to the URI %s", URI)
+			URI = "mongodb://" + URI
+		}
+
+		servers[serverIdx] = buildExporter(opts, URI, log)
+	}
+
+	return servers
+}
+
+func buildURI(uri string, user string, password string) string {
+	// IF user@pass not contained in uri AND custom user and pass supplied in arguments
+	// DO concat a new uri with user and pass arguments value
+	if !strings.Contains(uri, "@") && user != "" && password != "" {
+		// trim mongodb:// prefix to handle user and pass logic
+		uri = strings.TrimPrefix(uri, "mongodb://")
+		// add user and pass to the uri
+		uri = fmt.Sprintf("%s:%s@%s", user, password, uri)
+	}
+	if !strings.HasPrefix(uri, "mongodb") {
+		uri = "mongodb://" + uri
+	}
+
+	return uri
+}
diff --git a/main_test.go b/main_test.go
index bf37e38a0..a5549e1bb 100644
--- a/main_test.go
+++ b/main_test.go
@@ -18,6 +18,7 @@ package main
 import (
 	"testing"
 
+	"github.com/sirupsen/logrus"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -25,7 +26,6 @@ func TestBuildExporter(t *testing.T) {
 	opts := GlobalFlags{
 		CollStatsNamespaces:   "c1,c2,c3",
 		IndexStatsCollections: "i1,i2,i3",
-		URI:                   "mongodb://usr:pwd@127.0.0.1/",
 		GlobalConnPool:        false, // to avoid testing the connection
 		WebListenAddress:      "localhost:12345",
 		WebTelemetryPath:      "/mymetrics",
@@ -36,8 +36,8 @@ func TestBuildExporter(t *testing.T) {
 
 		CompatibleMode: true,
 	}
-
-	buildExporter(opts)
+	log := logrus.New()
+	buildExporter(opts, "mongodb://usr:pwd@127.0.0.1/", log)
 }
 
 func TestBuildURI(t *testing.T) {