added a check for oid and name to prevent empty metrics (#9366)

(cherry picked from commit b846c50)

plugins/inputs/snmp/snmp.go

@@ -173,6 +173,12 @@ type Table struct {
 
 // Init() builds & initializes the nested fields.
 func (t *Table) Init() error {
+	//makes sure oid or name is set in config file
+	//otherwise snmp will produce metrics with an empty name
+	if t.Oid == "" && t.Name == "" {
+		return fmt.Errorf("SNMP table in config file is not named. One or both of the oid and name settings must be set")
+	}
+
 	if t.initialized {
 		return nil
 	}

plugins/inputs/snmp/snmp_test.go

@@ -199,11 +199,12 @@ func TestSnmpInit_noTranslate(t *testing.T) {
 			{Oid: ".1.1.1.3"},
 		},
 		Tables: []Table{
-			{Fields: []Field{
-				{Oid: ".1.1.1.4", Name: "four", IsTag: true},
-				{Oid: ".1.1.1.5", Name: "five"},
-				{Oid: ".1.1.1.6"},
-			}},
+			{Name: "testing",
+				Fields: []Field{
+					{Oid: ".1.1.1.4", Name: "four", IsTag: true},
+					{Oid: ".1.1.1.5", Name: "five"},
+					{Oid: ".1.1.1.6"},
+				}},
 		},
 	}
 
@@ -235,6 +236,21 @@ func TestSnmpInit_noTranslate(t *testing.T) {
 	assert.Equal(t, false, s.Tables[0].Fields[2].IsTag)
 }
 
+func TestSnmpInit_noName_noOid(t *testing.T) {
+	s := &Snmp{
+		Tables: []Table{
+			{Fields: []Field{
+				{Oid: ".1.1.1.4", Name: "four", IsTag: true},
+				{Oid: ".1.1.1.5", Name: "five"},
+				{Oid: ".1.1.1.6"},
+			}},
+		},
+	}
+
+	err := s.init()
+	require.Error(t, err)
+}
+
 func TestGetSNMPConnection_v2(t *testing.T) {
 	s := &Snmp{
 		Agents: []string{"1.2.3.4:567", "1.2.3.4", "udp://127.0.0.1"},