ensure proper context on snmp error messages (influxdata#2220)

CHANGELOG.md

@@ -105,6 +105,7 @@ plugins, not just statsd.
 - [#1973](https://github.com/influxdata/telegraf/issues/1973): Partial fix: logparser CLF pattern with IPv6 addresses.
 - [#1975](https://github.com/influxdata/telegraf/issues/1975) & [#2102](https://github.com/influxdata/telegraf/issues/2102): Fix thread-safety when using multiple instances of the statsd input plugin.
 - [#2027](https://github.com/influxdata/telegraf/issues/2027): docker input: interface conversion panic fix.
+- [#1814](https://github.com/influxdata/telegraf/issues/1814): snmp: ensure proper context is present on error messages
 
 ## v1.1.2 [2016-12-12]
 

plugins/inputs/snmp/snmp.go

@@ -146,13 +146,13 @@ func (s *Snmp) init() error {
 
 	for i := range s.Tables {
 		if err := s.Tables[i].init(); err != nil {
-			return err
+			return Errorf(err, "initializing table %s", s.Tables[i].Name)
 		}
 	}
 
 	for i := range s.Fields {
 		if err := s.Fields[i].init(); err != nil {
-			return err
+			return Errorf(err, "initializing field %s", s.Fields[i].Name)
 		}
 	}
 
@@ -192,7 +192,7 @@ func (t *Table) init() error {
 	// initialize all the nested fields
 	for i := range t.Fields {
 		if err := t.Fields[i].init(); err != nil {
-			return err
+			return Errorf(err, "initializing field %s", t.Fields[i].Name)
 		}
 	}
 
@@ -210,7 +210,7 @@ func (t *Table) initBuild() error {
 
 	_, _, oidText, fields, err := snmpTable(t.Oid)
 	if err != nil {
-		return Errorf(err, "initializing table %s", t.Oid)
+		return err
 	}
 	if t.Name == "" {
 		t.Name = oidText
@@ -252,7 +252,7 @@ func (f *Field) init() error {
 
 	_, oidNum, oidText, conversion, err := snmpTranslate(f.Oid)
 	if err != nil {
-		return Errorf(err, "translating %s", f.Oid)
+		return Errorf(err, "translating")
 	}
 	f.Oid = oidNum
 	if f.Name == "" {
@@ -358,7 +358,7 @@ func (s *Snmp) Gather(acc telegraf.Accumulator) error {
 		// Now is the real tables.
 		for _, t := range s.Tables {
 			if err := s.gatherTable(acc, gs, t, topTags, true); err != nil {
-				acc.AddError(Errorf(err, "agent %s", agent))
+				acc.AddError(Errorf(err, "agent %s: gathering table %s", agent, t.Name))
 			}
 		}
 	}
@@ -406,7 +406,7 @@ func (t Table) Build(gs snmpConnection, walk bool) (*RTable, error) {
 		}
 
 		if len(f.Oid) == 0 {
-			return nil, fmt.Errorf("cannot have empty OID")
+			return nil, fmt.Errorf("cannot have empty OID on field %s", f.Name)
 		}
 		var oid string
 		if f.Oid[0] == '.' {
@@ -426,12 +426,12 @@ func (t Table) Build(gs snmpConnection, walk bool) (*RTable, error) {
 			// empty string. This results in all the non-table fields sharing the same
 			// index, and being added on the same row.
 			if pkt, err := gs.Get([]string{oid}); err != nil {
-				return nil, Errorf(err, "performing get")
+				return nil, Errorf(err, "performing get on field %s", f.Name)
 			} else if pkt != nil && len(pkt.Variables) > 0 && pkt.Variables[0].Type != gosnmp.NoSuchObject && pkt.Variables[0].Type != gosnmp.NoSuchInstance {
 				ent := pkt.Variables[0]
 				fv, err := fieldConvert(f.Conversion, ent.Value)
 				if err != nil {
-					return nil, Errorf(err, "converting %q", ent.Value)
+					return nil, Errorf(err, "converting %q (OID %s) for field %s", ent.Value, ent.Name, f.Name)
 				}
 				if fvs, ok := fv.(string); !ok || fvs != "" {
 					ifv[""] = fv
@@ -454,7 +454,7 @@ func (t Table) Build(gs snmpConnection, walk bool) (*RTable, error) {
 
 				fv, err := fieldConvert(f.Conversion, ent.Value)
 				if err != nil {
-					return Errorf(err, "converting %q", ent.Value)
+					return Errorf(err, "converting %q (OID %s) for field %s", ent.Value, ent.Name, f.Name)
 				}
 				if fvs, ok := fv.(string); !ok || fvs != "" {
 					ifv[idx] = fv
@@ -463,7 +463,7 @@ func (t Table) Build(gs snmpConnection, walk bool) (*RTable, error) {
 			})
 			if err != nil {
 				if _, ok := err.(NestedError); !ok {
-					return nil, Errorf(err, "performing bulk walk")
+					return nil, Errorf(err, "performing bulk walk for field %s", f.Name)
 				}
 			}
 		}