added snmp walk cache again

core/network/snmp_client.go

@@ -19,9 +19,10 @@ import (
 
 // SNMPClient is used to communicate via snmp.
 type SNMPClient struct {
-	client   *gosnmp.GoSNMP
-	useCache bool
-	getCache requestCache
+	client    *gosnmp.GoSNMP
+	useCache  bool
+	getCache  requestCache
+	walkCache requestCache
 }
 
 type snmpClientCreation struct {
@@ -269,9 +270,10 @@ func newSNMPClientTestConnection(client *gosnmp.GoSNMP) (*SNMPClient, error) {
 	client.ExponentialTimeout = true
 
 	return &SNMPClient{
-		client:   client,
-		useCache: true,
-		getCache: newRequestCache(),
+		client:    client,
+		useCache:  true,
+		getCache:  newRequestCache(),
+		walkCache: newRequestCache(),
 	}, nil
 }
 
@@ -413,6 +415,17 @@ func (s *SNMPClient) SNMPGet(ctx context.Context, oid ...string) ([]SNMPResponse
 
 // SNMPWalk sends a snmpwalk request to the specified oid.
 func (s *SNMPClient) SNMPWalk(ctx context.Context, oid string) ([]SNMPResponse, error) {
+	if s.useCache {
+		x, err := s.walkCache.get(oid)
+		if err == nil {
+			res, ok := x.res.([]SNMPResponse)
+			if !ok {
+				return nil, errors.New("cached snmp result is not a snmp response")
+			}
+			return res, nil
+		}
+	}
+
 	s.client.Context = ctx
 
 	var response []gosnmp.SnmpPDU
@@ -428,11 +441,17 @@ func (s *SNMPClient) SNMPWalk(ctx context.Context, oid string) ([]SNMPResponse,
 	}
 	if err != nil {
 		err = errors.Wrap(err, "snmpwalk failed")
+		if s.useCache {
+			s.walkCache.add(oid, nil, err)
+		}
 		return nil, err
 	}
 
 	if response == nil {
 		err = tholaerr.NewNotFoundError("No Such Object available on this agent at this OID")
+		if s.useCache {
+			s.walkCache.add(oid, nil, err)
+		}
 		return nil, err
 	}
 
@@ -454,6 +473,10 @@ func (s *SNMPClient) SNMPWalk(ctx context.Context, oid string) ([]SNMPResponse,
 		}
 	}
 
+	if s.useCache {
+		s.walkCache.add(oid, res, nil)
+	}
+
 	return res, nil
 }