Add RabbitMQ slave_nodes and synchronized_slave_nodes metrics (#7084)

plugins/inputs/rabbitmq/README.md

@@ -173,7 +173,9 @@ For additional details reference the [RabbitMQ Management HTTP Stats][management
     - messages_ready (int, count)
     - messages_redeliver (int, count)
     - messages_redeliver_rate (float, messages per second)
-    - messages_unack (integer, count)
+    - messages_unack (int, count)
+    - slave_nodes (int, count)
+    - synchronised_slave_nodes (int, count)
 
 + rabbitmq_exchange
   - tags:

plugins/inputs/rabbitmq/rabbitmq.go

@@ -132,6 +132,8 @@ type Queue struct {
 	Durable                bool
 	AutoDelete             bool     `json:"auto_delete"`
 	IdleSince              string   `json:"idle_since"`
+	SlaveNodes             []string `json:"slave_nodes"`
+	SynchronisedSlaveNodes []string `json:"synchronised_slave_nodes"`
 }
 
 // Node ...
@@ -588,6 +590,8 @@ func gatherQueues(r *RabbitMQ, acc telegraf.Accumulator) {
 				"consumers":                queue.Consumers,
 				"consumer_utilisation":     queue.ConsumerUtilisation,
 				"idle_since":               queue.IdleSince,
+				"slave_nodes":              len(queue.SlaveNodes),
+				"synchronised_slave_nodes": len(queue.SynchronisedSlaveNodes),
 				"memory":                   queue.Memory,
 				// messages information
 				"message_bytes":             queue.MessageBytes,

plugins/inputs/rabbitmq/rabbitmq_test.go

@@ -98,6 +98,8 @@ func TestRabbitMQGeneratesMetrics(t *testing.T) {
 		"messages_redeliver":        33,
 		"messages_redeliver_rate":   2.5,
 		"idle_since":                "2015-11-01 8:22:14",
+		"slave_nodes":               1,
+		"synchronised_slave_nodes":  1,
 	}
 	compareMetrics(t, queuesMetrics, acc, "rabbitmq_queue")
 

plugins/inputs/rabbitmq/testdata/queues.json

@@ -109,6 +109,12 @@
     "exclusive_consumer_tag": null,
     "effective_policy_definition": [],
     "operator_policy": null,
-    "policy": null
+    "policy": null,
+    "slave_nodes":[
+      "rabbit@ip-10-1-2-118"
+    ],
+    "synchronised_slave_nodes":[
+      "rabbit@ip-10-1-2-118"
+    ]
   }
 ]