Add replica set tag to mongodb input (#6914)

plugins/inputs/mongodb/README.md

@@ -56,6 +56,7 @@ by running Telegraf with the `--debug` argument.
   - tags:
     - hostname
     - node_type
+    - rs_name
   - fields:
     - active_reads (integer)
     - active_writes (integer)

plugins/inputs/mongodb/mongodb_data.go

@@ -245,6 +245,10 @@ func (d *MongodbData) AddDefaultStats() {
 		d.addStat(statLine, DefaultLatencyStats)
 	}
 
+	if d.StatLine.ReplSetName != "" {
+		d.Tags["rs_name"] = d.StatLine.ReplSetName
+	}
+
 	if d.StatLine.OplogStats != nil {
 		d.add("repl_oplog_window_sec", d.StatLine.OplogStats.TimeDiff)
 	}

plugins/inputs/mongodb/mongodb_data_test.go

@@ -211,12 +211,14 @@ func TestStateTag(t *testing.T) {
 			Query:         0,
 			NodeType:      "PRI",
 			NodeState:     "PRIMARY",
+			ReplSetName:   "rs1",
 		},
 		tags,
 	)
 
 	stateTags := make(map[string]string)
 	stateTags["node_type"] = "PRI"
+	stateTags["rs_name"] = "rs1"
 
 	var acc testutil.Accumulator