Refactor code: clear old OIDs in the Session before updating them

src/ifmib/ifmib.go

@@ -5,6 +5,7 @@ package ifmib
 import (
 	"fmt"
 	"os"
+	"reflect"
 	"sync"
 	"time"
 
@@ -161,14 +162,32 @@ func (m *InterfaceMIB) UpdateInterfaceDetails(details []vpp.InterfaceDetails) {
 	logger.Debugf("Interface details updated for %d interfaces", len(details))
 }
 
+func (m *InterfaceMIB) clearHandler() {
+	// Use reflection to access and clear the private fields of ListHandler
+	// since it doesn't have a Clear() method
+	handlerValue := reflect.ValueOf(m.handler).Elem()
+
+	oidsField := handlerValue.FieldByName("oids")
+	itemsField := handlerValue.FieldByName("items")
+
+	if oidsField.IsValid() && oidsField.CanSet() {
+		oidsField.Set(reflect.Zero(oidsField.Type()))
+	}
+
+	if itemsField.IsValid() && itemsField.CanSet() {
+		itemsField.Set(reflect.Zero(itemsField.Type()))
+	}
+}
+
 func (m *InterfaceMIB) UpdateStats(interfaceStats *api.InterfaceStats) {
 	m.mutex.Lock()
 	defer m.mutex.Unlock()
 
 	logger.Debugf("Updating IF-MIB with %d interfaces", len(interfaceStats.Interfaces))
 
-	// Clear existing entries
-	m.handler = &agentx.ListHandler{}
+	// Clear existing entries while preserving the handler reference
+	// Since go-agentx 0.3.0 binds handlers to sessions at creation time
+	m.clearHandler()
 	m.stats = make(map[uint32]*api.InterfaceCounters)
 
 	// Add new entries
@@ -178,11 +197,7 @@ func (m *InterfaceMIB) UpdateStats(interfaceStats *api.InterfaceStats) {
 		m.addInterfaceToMIB(&iface)
 	}
 
-	// Note: With go-agentx 0.3.0, handlers are set during session creation and cannot be changed
-	if m.ifXTableSession != nil {
 	logger.Printf("Updated IF-MIB data for %d interfaces", len(m.stats))
-	}
-
 	logger.Debugf("IF-MIB now contains %d interfaces", len(m.stats))
 }