feat(controller): decouple A2A handler registration from controller reconcilation

go/internal/a2a/a2a_registrar.go

@@ -0,0 +1,168 @@
+package a2a
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"net/http"
+	"os"
+	"reflect"
+	"time"
+
+	"github.com/go-logr/logr"
+	"github.com/kagent-dev/kagent/go/api/v1alpha2"
+	agent_translator "github.com/kagent-dev/kagent/go/internal/controller/translator/agent"
+	authimpl "github.com/kagent-dev/kagent/go/internal/httpserver/auth"
+	common "github.com/kagent-dev/kagent/go/internal/utils"
+	"github.com/kagent-dev/kagent/go/pkg/auth"
+	"k8s.io/apimachinery/pkg/types"
+	"k8s.io/client-go/tools/cache"
+	crcache "sigs.k8s.io/controller-runtime/pkg/cache"
+	ctrllog "sigs.k8s.io/controller-runtime/pkg/log"
+	"sigs.k8s.io/controller-runtime/pkg/manager"
+	a2aclient "trpc.group/trpc-go/trpc-a2a-go/client"
+)
+
+type A2ARegistrar struct {
+	cache          crcache.Cache
+	translator     agent_translator.AdkApiTranslator
+	handlerMux     A2AHandlerMux
+	a2aBaseUrl     string
+	authenticator  auth.AuthProvider
+	a2aBaseOptions []a2aclient.Option
+}
+
+var _ manager.Runnable = (*A2ARegistrar)(nil)
+
+func NewA2ARegistrar(
+	cache crcache.Cache,
+	translator agent_translator.AdkApiTranslator,
+	mux A2AHandlerMux,
+	a2aBaseUrl string,
+	authenticator auth.AuthProvider,
+	streamingMaxBuf int,
+	streamingInitialBuf int,
+	streamingTimeout time.Duration,
+) *A2ARegistrar {
+	reg := &A2ARegistrar{
+		cache:         cache,
+		translator:    translator,
+		handlerMux:    mux,
+		a2aBaseUrl:    a2aBaseUrl,
+		authenticator: authenticator,
+		a2aBaseOptions: []a2aclient.Option{
+			a2aclient.WithTimeout(streamingTimeout),
+			a2aclient.WithBuffer(streamingInitialBuf, streamingMaxBuf),
+			debugOpt(),
+		},
+	}
+
+	return reg
+}
+
+func (a *A2ARegistrar) NeedLeaderElection() bool {
+	return false
+}
+
+func (a *A2ARegistrar) Start(ctx context.Context) error {
+	log := ctrllog.FromContext(ctx).WithName("a2a-registrar")
+
+	informer, err := a.cache.GetInformer(ctx, &v1alpha2.Agent{})
+	if err != nil {
+		return fmt.Errorf("failed to get cache informer: %w", err)
+	}
+
+	if _, err := informer.AddEventHandler(cache.ResourceEventHandlerFuncs{
+		AddFunc: func(obj interface{}) {
+			if agent, ok := obj.(*v1alpha2.Agent); ok {
+				if err := a.upsertAgentHandler(ctx, agent, log); err != nil {
+					log.Error(err, "failed to upsert A2A handler", "agent", common.GetObjectRef(agent))
+				}
+			}
+		},
+		UpdateFunc: func(oldObj, newObj interface{}) {
+			oldAgent, ok1 := oldObj.(*v1alpha2.Agent)
+			newAgent, ok2 := newObj.(*v1alpha2.Agent)
+			if !ok1 || !ok2 {
+				return
+			}
+			if oldAgent.Generation != newAgent.Generation || !reflect.DeepEqual(oldAgent.Spec, newAgent.Spec) {
+				if err := a.upsertAgentHandler(ctx, newAgent, log); err != nil {
+					log.Error(err, "failed to upsert A2A handler", "agent", common.GetObjectRef(newAgent))
+				}
+			}
+		},
+		DeleteFunc: func(obj interface{}) {
+			agent, ok := obj.(*v1alpha2.Agent)
+			if !ok {
+				if tombstone, ok := obj.(cache.DeletedFinalStateUnknown); ok {
+					if a2, ok := tombstone.Obj.(*v1alpha2.Agent); ok {
+						agent = a2
+					}
+				}
+			}
+			if agent == nil {
+				return
+			}
+			ref := common.GetObjectRef(agent)
+			a.handlerMux.RemoveAgentHandler(ref)
+			log.V(1).Info("removed A2A handler", "agent", ref)
+		},
+	}); err != nil {
+		return fmt.Errorf("failed to add informer event handler: %w", err)
+	}
+
+	if ok := a.cache.WaitForCacheSync(ctx); !ok {
+		return fmt.Errorf("cache sync failed")
+	}
+
+	<-ctx.Done()
+	return nil
+}
+
+func (a *A2ARegistrar) upsertAgentHandler(ctx context.Context, agent *v1alpha2.Agent, log logr.Logger) error {
+	agentRef := types.NamespacedName{Namespace: agent.GetNamespace(), Name: agent.GetName()}
+	card := agent_translator.GetA2AAgentCard(agent)
+
+	client, err := a2aclient.NewA2AClient(
+		card.URL,
+		append(
+			a.a2aBaseOptions,
+			a2aclient.WithHTTPReqHandler(
+				authimpl.A2ARequestHandler(
+					a.authenticator,
+					agentRef,
+				),
+			),
+		)...,
+	)
+	if err != nil {
+		return fmt.Errorf("create A2A client for %s: %w", agentRef, err)
+	}
+
+	cardCopy := *card
+	cardCopy.URL = fmt.Sprintf("%s/%s/", a.a2aBaseUrl, agentRef)
+
+	if err := a.handlerMux.SetAgentHandler(agentRef.String(), client, cardCopy); err != nil {
+		return fmt.Errorf("set handler for %s: %w", agentRef, err)
+	}
+
+	log.V(1).Info("registered/updated A2A handler", "agent", agentRef)
+	return nil
+}
+
+func debugOpt() a2aclient.Option {
+	debugAddr := os.Getenv("KAGENT_A2A_DEBUG_ADDR")
+	if debugAddr != "" {
+		client := new(http.Client)
+		client.Transport = &http.Transport{
+			DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
+				var zeroDialer net.Dialer
+				return zeroDialer.DialContext(ctx, network, debugAddr)
+			},
+		}
+		return a2aclient.WithHTTPClient(client)
+	} else {
+		return func(*a2aclient.A2AClient) {}
+	}
+}

go/internal/controller/reconciler/reconciler.go

@@ -19,10 +19,8 @@ import (
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime/schema"
 	"k8s.io/client-go/util/retry"
-	"trpc.group/trpc-go/trpc-a2a-go/server"
 
 	"github.com/kagent-dev/kagent/go/api/v1alpha2"
-	"github.com/kagent-dev/kagent/go/internal/controller/a2a"
 	"github.com/kagent-dev/kagent/go/internal/controller/translator"
 	agent_translator "github.com/kagent-dev/kagent/go/internal/controller/translator/agent"
 	"github.com/kagent-dev/kagent/go/internal/database"
@@ -53,7 +51,6 @@ type KagentReconciler interface {
 
 type kagentReconciler struct {
 	adkTranslator agent_translator.AdkApiTranslator
-	a2aReconciler a2a.A2AReconciler
 
 	kube     client.Client
 	dbClient database.Client
@@ -69,14 +66,12 @@ func NewKagentReconciler(
 	kube client.Client,
 	dbClient database.Client,
 	defaultModelConfig types.NamespacedName,
-	a2aReconciler a2a.A2AReconciler,
 ) KagentReconciler {
 	return &kagentReconciler{
 		adkTranslator:      translator,
 		kube:               kube,
 		dbClient:           dbClient,
 		defaultModelConfig: defaultModelConfig,
-		a2aReconciler:      a2aReconciler,
 	}
 }
 
@@ -100,9 +95,6 @@ func (a *kagentReconciler) ReconcileKagentAgent(ctx context.Context, req ctrl.Re
 }
 
 func (a *kagentReconciler) handleAgentDeletion(req ctrl.Request) error {
-	// remove a2a handler if it exists
-	a.a2aReconciler.ReconcileAgentDeletion(req.String())
-
 	if err := a.dbClient.DeleteAgent(req.String()); err != nil {
 		return fmt.Errorf("failed to delete agent %s: %w",
 			req.String(), err)
@@ -499,10 +491,6 @@ func (a *kagentReconciler) reconcileAgent(ctx context.Context, agent *v1alpha2.A
 		return fmt.Errorf("failed to reconcile owned objects: %v", err)
 	}
 
-	if err := a.reconcileA2A(ctx, agent, agentOutputs.AgentCard); err != nil {
-		return fmt.Errorf("failed to reconcile A2A for agent %s/%s: %v", agent.Namespace, agent.Name, err)
-	}
-
 	if err := a.upsertAgent(ctx, agent, agentOutputs); err != nil {
 		return fmt.Errorf("failed to upsert agent %s/%s: %v", agent.Namespace, agent.Name, err)
 	}
@@ -744,14 +732,6 @@ func (a *kagentReconciler) getDiscoveredMCPTools(ctx context.Context, serverRef
 	return discoveredTools, nil
 }
 
-func (a *kagentReconciler) reconcileA2A(
-	ctx context.Context,
-	agent *v1alpha2.Agent,
-	card server.AgentCard,
-) error {
-	return a.a2aReconciler.ReconcileAgent(ctx, agent, card)
-}
-
 func convertTool(tool *database.Tool) (*v1alpha2.MCPTool, error) {
 	return &v1alpha2.MCPTool{
 		Name:        tool.ID,