[amqp output] Allow external auth (cert-based tls auth)

closes #863

CHANGELOG.md

@@ -1,6 +1,7 @@
 ## v0.11.2 [unreleased]
 
 ### Features
+- [#863](https://github.com/influxdata/telegraf/pull/863): AMQP output: allow external auth. Thanks @ekini!
 - [#707](https://github.com/influxdata/telegraf/pull/707): Improved prometheus plugin. Thanks @titilambert!
 
 ### Bugfixes

internal/internal.go

@@ -109,6 +109,7 @@ func GetTLSConfig(
 			RootCAs:            caCertPool,
 			InsecureSkipVerify: InsecureSkipVerify,
 		}
+		t.BuildNameToCertificate()
 	} else {
 		if InsecureSkipVerify {
 			t.InsecureSkipVerify = true

plugins/outputs/amqp/amqp.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"fmt"
 	"log"
+	"strings"
 	"sync"
 	"time"
 
@@ -20,6 +21,8 @@ type AMQP struct {
 	URL string
 	// AMQP exchange
 	Exchange string
+	// AMQP Auth method
+	AuthMethod string
 	// Routing Key Tag
 	RoutingTag string `toml:"routing_tag"`
 	// InfluxDB database
@@ -45,7 +48,17 @@ type AMQP struct {
 	serializer serializers.Serializer
 }
 
+type externalAuth struct{}
+
+func (a *externalAuth) Mechanism() string {
+	return "EXTERNAL"
+}
+func (a *externalAuth) Response() string {
+	return fmt.Sprintf("\000")
+}
+
 const (
+	DefaultAuthMethod      = "PLAIN"
 	DefaultRetentionPolicy = "default"
 	DefaultDatabase        = "telegraf"
 	DefaultPrecision       = "s"
@@ -56,6 +69,8 @@ var sampleConfig = `
   url = "amqp://localhost:5672/influxdb"
   ## AMQP exchange
   exchange = "telegraf"
+  ## Auth method. PLAIN and EXTERNAL are supported
+  # auth_method = "PLAIN"
   ## Telegraf tag to use as a routing key
   ##  ie, if this tag exists, it's value will be used as the routing key
   routing_tag = "host"
@@ -103,11 +118,19 @@ func (q *AMQP) Connect() error {
 		return err
 	}
 
-	if tls != nil {
-		connection, err = amqp.DialTLS(q.URL, tls)
-	} else {
-		connection, err = amqp.Dial(q.URL)
+	// parse auth method
+	var sasl []amqp.Authentication // nil by default
+
+	if strings.ToUpper(q.AuthMethod) == "EXTERNAL" {
+		sasl = []amqp.Authentication{&externalAuth{}}
 	}
+
+	amqpConf := amqp.Config{
+		TLSClientConfig: tls,
+		SASL:            sasl, // if nil, it will be PLAIN
+	}
+
+	connection, err = amqp.DialConfig(q.URL, amqpConf)
 	if err != nil {
 		return err
 	}
@@ -200,6 +223,7 @@ func (q *AMQP) Write(metrics []telegraf.Metric) error {
 func init() {
 	outputs.Add("amqp", func() telegraf.Output {
 		return &AMQP{
+			AuthMethod:      DefaultAuthMethod,
 			Database:        DefaultDatabase,
 			Precision:       DefaultPrecision,
 			RetentionPolicy: DefaultRetentionPolicy,