Support passive queue declaration in amqp_consumer (#5831)

plugins/inputs/amqp_consumer/README.md

@@ -27,7 +27,7 @@ The following defaults are known to work with RabbitMQ:
   # username = ""
   # password = ""
 
-  ## Exchange to declare and consume from.
+  ## Name of the exchange to declare.  If unset, no exchange will be declared.
   exchange = "telegraf"
 
   ## Exchange type; common types are "direct", "fanout", "topic", "header", "x-consistent-hash".
@@ -49,7 +49,11 @@ The following defaults are known to work with RabbitMQ:
   ## AMQP queue durability can be "transient" or "durable".
   queue_durability = "durable"
 
-  ## Binding Key
+  ## If true, queue will be passively declared.
+  # queue_passive = false
+
+  ## A binding between the exchange and queue using this binding key is
+  ## created.  If unset, no binding is created.
   binding_key = "#"
 
   ## Maximum number of messages server should give to the worker.

plugins/inputs/amqp_consumer/amqp_consumer.go

@@ -41,6 +41,7 @@ type AMQPConsumer struct {
 	// Queue Name
 	Queue           string `toml:"queue"`
 	QueueDurability string `toml:"queue_durability"`
+	QueuePassive    bool   `toml:"queue_passive"`
 
 	// Binding Key
 	BindingKey string `toml:"binding_key"`
@@ -101,7 +102,7 @@ func (a *AMQPConsumer) SampleConfig() string {
   # username = ""
   # password = ""
 
-  ## Exchange to declare and consume from.
+  ## Name of the exchange to declare.  If unset, no exchange will be declared.
   exchange = "telegraf"
 
   ## Exchange type; common types are "direct", "fanout", "topic", "header", "x-consistent-hash".
@@ -123,7 +124,11 @@ func (a *AMQPConsumer) SampleConfig() string {
   ## AMQP queue durability can be "transient" or "durable".
   queue_durability = "durable"
 
-  ## Binding Key.
+  ## If true, queue will be passively declared.
+  # queue_passive = false
+
+  ## A binding between the exchange and queue using this binding key is
+  ## created.  If unset, no binding is created.
   binding_key = "#"
 
   ## Maximum number of messages server should give to the worker.
@@ -286,6 +291,7 @@ func (a *AMQPConsumer) connect(amqpConf *amqp.Config) (<-chan amqp.Delivery, err
 		return nil, fmt.Errorf("Failed to open a channel: %s", err)
 	}
 
+	if a.Exchange != "" {
 		var exchangeDurable = true
 		switch a.ExchangeDurability {
 		case "transient":
@@ -309,27 +315,18 @@ func (a *AMQPConsumer) connect(amqpConf *amqp.Config) (<-chan amqp.Delivery, err
 		if err != nil {
 			return nil, err
 		}
-
-	var queueDurable = true
-	switch a.QueueDurability {
-	case "transient":
-		queueDurable = false
-	default:
-		queueDurable = true
 	}
 
-	q, err := ch.QueueDeclare(
+	q, err := declareQueue(
-		a.Queue,      // queue
+		ch,
-		queueDurable, // durable
+		a.Queue,
-		false,        // delete when unused
+		a.QueueDurability,
-		false,        // exclusive
+		a.QueuePassive)
-		false,        // no-wait
-		nil,          // arguments
-	)
 	if err != nil {
-		return nil, fmt.Errorf("Failed to declare a queue: %s", err)
+		return nil, err
 	}
 
+	if a.BindingKey != "" {
 		err = ch.QueueBind(
 			q.Name,       // queue
 			a.BindingKey, // binding-key
@@ -340,6 +337,7 @@ func (a *AMQPConsumer) connect(amqpConf *amqp.Config) (<-chan amqp.Delivery, err
 		if err != nil {
 			return nil, fmt.Errorf("Failed to bind a queue: %s", err)
 		}
+	}
 
 	err = ch.Qos(
 		a.PrefetchCount,
@@ -402,6 +400,48 @@ func declareExchange(
 	return nil
 }
 
+func declareQueue(
+	channel *amqp.Channel,
+	queueName string,
+	queueDurability string,
+	queuePassive bool,
+) (*amqp.Queue, error) {
+	var queue amqp.Queue
+	var err error
+
+	var queueDurable = true
+	switch queueDurability {
+	case "transient":
+		queueDurable = false
+	default:
+		queueDurable = true
+	}
+
+	if queuePassive {
+		queue, err = channel.QueueDeclarePassive(
+			queueName,    // queue
+			queueDurable, // durable
+			false,        // delete when unused
+			false,        // exclusive
+			false,        // no-wait
+			nil,          // arguments
+		)
+	} else {
+		queue, err = channel.QueueDeclare(
+			queueName,    // queue
+			queueDurable, // durable
+			false,        // delete when unused
+			false,        // exclusive
+			false,        // no-wait
+			nil,          // arguments
+		)
+	}
+	if err != nil {
+		return nil, fmt.Errorf("error declaring queue: %v", err)
+	}
+	return &queue, nil
+}
+
 // Read messages from queue and add them to the Accumulator
 func (a *AMQPConsumer) process(ctx context.Context, msgs <-chan amqp.Delivery, ac telegraf.Accumulator) {
 	a.deliveries = make(map[telegraf.TrackingID]amqp.Delivery)

plugins/outputs/amqp/README.md

@@ -33,7 +33,7 @@ For an introduction to AMQP see:
   # exchange_type = "topic"
 
   ## If true, exchange will be passively declared.
-  # exchange_declare_passive = false
+  # exchange_passive = false
 
   ## Exchange durability can be either "transient" or "durable".
   # exchange_durability = "durable"

plugins/outputs/amqp/amqp.go

@@ -92,7 +92,7 @@ var sampleConfig = `
   # exchange_type = "topic"
 
   ## If true, exchange will be passively declared.
-  # exchange_declare_passive = false
+  # exchange_passive = false
 
   ## Exchange durability can be either "transient" or "durable".
   # exchange_durability = "durable"

plugins/outputs/amqp/client.go

@@ -78,6 +78,10 @@ func Connect(config *ClientConfig) (*client, error) {
 }
 
 func (c *client) DeclareExchange() error {
+	if c.config.exchange == "" {
+		return nil
+	}
+
 	var err error
 	if c.config.exchangePassive {
 		err = c.channel.ExchangeDeclarePassive(