add oid_index_suffix to snmp plugin

CHANGELOG.md

@@ -22,6 +22,7 @@
 - [#1699](https://github.com/influxdata/telegraf/pull/1699): Add database blacklist option for Postgresql
 - [#1791](https://github.com/influxdata/telegraf/pull/1791): Add Docker container state metrics to Docker input plugin output
 - [#1755](https://github.com/influxdata/telegraf/issues/1755): Add support to SNMP for IP & MAC address conversion.
+- [#1729](https://github.com/influxdata/telegraf/issues/1729): Add support to SNMP for OID index suffixes.
 
 ### Bugfixes
 

plugins/inputs/snmp/README.md

@@ -136,6 +136,9 @@ Output measurement name.
 * `oid`:  
 OID to get. May be a numeric or textual OID.
 
+* `oid_index_suffix`:
+The OID sub-identifier to strip off so that the index can be matched against other fields in the table.
+
 * `name`:  
 Output field/tag name.
 If not specified, it defaults to the value of `oid`. If `oid` is numeric, an attempt to translate the numeric OID into a texual OID will be made.

plugins/inputs/snmp/snmp.go

@@ -258,6 +258,8 @@ type Field struct {
 	// off the OID prefix, and use the remainder as the index. For multiple fields
 	// to show up in the same row, they must share the same index.
 	Oid string
+	// OidIndexSuffix is the trailing sub-identifier on a table record OID that will be stripped off to get the record's index.
+	OidIndexSuffix string
 	// IsTag controls whether this OID is output as a tag or a value.
 	IsTag bool
 	// Conversion controls any type conversion that is done on the value.
@@ -460,18 +462,28 @@ func (t Table) Build(gs snmpConnection, walk bool) (*RTable, error) {
 				if err != nil {
 					return nil, Errorf(err, "converting %q", ent.Value)
 				}
-				ifv[ent.Name[len(oid):]] = fv
+				ifv[""] = fv
 			}
 		} else {
 			err := gs.Walk(oid, func(ent gosnmp.SnmpPDU) error {
 				if len(ent.Name) <= len(oid) || ent.Name[:len(oid)+1] != oid+"." {
 					return NestedError{} // break the walk
 				}
+
+				idx := ent.Name[len(oid):]
+				if f.OidIndexSuffix != "" {
+					if !strings.HasSuffix(idx, f.OidIndexSuffix) {
+						// this entry doesn't match our OidIndexSuffix. skip it
+						return nil
+					}
+					idx = idx[:len(idx)-len(f.OidIndexSuffix)]
+				}
+
 				fv, err := fieldConvert(f.Conversion, ent.Value)
 				if err != nil {
 					return Errorf(err, "converting %q", ent.Value)
 				}
-				ifv[ent.Name[len(oid):]] = fv
+				ifv[idx] = fv
 				return nil
 			})
 			if err != nil {

plugins/inputs/snmp/snmp_test.go

@@ -72,6 +72,8 @@ var tsc = &testSNMPConnection{
 		".1.0.0.1.1":         "baz",
 		".1.0.0.1.2":         234,
 		".1.0.0.1.3":         []byte("byte slice"),
+		".1.0.0.2.1.5.0.9.9": 11,
+		".1.0.0.2.1.5.1.9.9": 22,
 	},
 }
 
@@ -371,6 +373,11 @@ func TestTableBuild_walk(t *testing.T) {
 				Oid:        ".1.0.0.0.1.3",
 				Conversion: "float",
 			},
+			{
+				Name:           "myfield4",
+				Oid:            ".1.0.0.2.1.5",
+				OidIndexSuffix: ".9.9",
+			},
 		},
 	}
 
@@ -380,11 +387,19 @@ func TestTableBuild_walk(t *testing.T) {
 	assert.Equal(t, tb.Name, "mytable")
 	rtr1 := RTableRow{
 		Tags: map[string]string{"myfield1": "foo"},
-		Fields: map[string]interface{}{"myfield2": 1, "myfield3": float64(0.123)},
+		Fields: map[string]interface{}{
+			"myfield2": 1,
+			"myfield3": float64(0.123),
+			"myfield4": 11,
+		},
 	}
 	rtr2 := RTableRow{
 		Tags: map[string]string{"myfield1": "bar"},
-		Fields: map[string]interface{}{"myfield2": 2, "myfield3": float64(0.456)},
+		Fields: map[string]interface{}{
+			"myfield2": 2,
+			"myfield3": float64(0.456),
+			"myfield4": 22,
+		},
 	}
 	assert.Len(t, tb.Rows, 2)
 	assert.Contains(t, tb.Rows, rtr1)