cmd/k8s-operator: split operator.go into svc.go/sts.go

Updates #502

Signed-off-by: Maisem Ali <maisem@tailscale.com>

cmd/k8s-operator/svc.go

@@ -0,0 +1,185 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package main
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	"go.uber.org/zap"
+	"golang.org/x/exp/slices"
+	corev1 "k8s.io/api/core/v1"
+	apierrors "k8s.io/apimachinery/pkg/api/errors"
+	"sigs.k8s.io/controller-runtime/pkg/client"
+	"sigs.k8s.io/controller-runtime/pkg/reconcile"
+)
+
+type ServiceReconciler struct {
+	client.Client
+	ssr    *tailscaleSTSReconciler
+	logger *zap.SugaredLogger
+}
+
+func childResourceLabels(parent *corev1.Service) map[string]string {
+	// You might wonder why we're using owner references, since they seem to be
+	// built for exactly this. Unfortunately, Kubernetes does not support
+	// cross-namespace ownership, by design. This means we cannot make the
+	// service being exposed the owner of the implementation details of the
+	// proxying. Instead, we have to do our own filtering and tracking with
+	// labels.
+	return map[string]string{
+		LabelManaged:         "true",
+		LabelParentName:      parent.GetName(),
+		LabelParentNamespace: parent.GetNamespace(),
+		LabelParentType:      "svc",
+	}
+}
+
+func (a *ServiceReconciler) Reconcile(ctx context.Context, req reconcile.Request) (_ reconcile.Result, err error) {
+	logger := a.logger.With("service-ns", req.Namespace, "service-name", req.Name)
+	logger.Debugf("starting reconcile")
+	defer logger.Debugf("reconcile finished")
+
+	svc := new(corev1.Service)
+	err = a.Get(ctx, req.NamespacedName, svc)
+	if apierrors.IsNotFound(err) {
+		// Request object not found, could have been deleted after reconcile request.
+		logger.Debugf("service not found, assuming it was deleted")
+		return reconcile.Result{}, nil
+	} else if err != nil {
+		return reconcile.Result{}, fmt.Errorf("failed to get svc: %w", err)
+	}
+	if !svc.DeletionTimestamp.IsZero() || !a.shouldExpose(svc) {
+		logger.Debugf("service is being deleted or should not be exposed, cleaning up")
+		return reconcile.Result{}, a.maybeCleanup(ctx, logger, svc)
+	}
+
+	return reconcile.Result{}, a.maybeProvision(ctx, logger, svc)
+}
+
+// maybeCleanup removes any existing resources related to serving svc over tailscale.
+//
+// This function is responsible for removing the finalizer from the service,
+// once all associated resources are gone.
+func (a *ServiceReconciler) maybeCleanup(ctx context.Context, logger *zap.SugaredLogger, svc *corev1.Service) error {
+	ix := slices.Index(svc.Finalizers, FinalizerName)
+	if ix < 0 {
+		logger.Debugf("no finalizer, nothing to do")
+		return nil
+	}
+
+	if done, err := a.ssr.Cleanup(ctx, logger, childResourceLabels(svc)); err != nil {
+		return fmt.Errorf("failed to cleanup: %w", err)
+	} else if !done {
+		logger.Debugf("cleanup not done yet, waiting for next reconcile")
+		return nil
+	}
+
+	svc.Finalizers = append(svc.Finalizers[:ix], svc.Finalizers[ix+1:]...)
+	if err := a.Update(ctx, svc); err != nil {
+		return fmt.Errorf("failed to remove finalizer: %w", err)
+	}
+
+	// Unlike most log entries in the reconcile loop, this will get printed
+	// exactly once at the very end of cleanup, because the final step of
+	// cleanup removes the tailscale finalizer, which will make all future
+	// reconciles exit early.
+	logger.Infof("unexposed service from tailnet")
+	return nil
+}
+
+// maybeProvision ensures that svc is exposed over tailscale, taking any actions
+// necessary to reach that state.
+//
+// This function adds a finalizer to svc, ensuring that we can handle orderly
+// deprovisioning later.
+func (a *ServiceReconciler) maybeProvision(ctx context.Context, logger *zap.SugaredLogger, svc *corev1.Service) error {
+	hostname, err := nameForService(svc)
+	if err != nil {
+		return err
+	}
+
+	if !slices.Contains(svc.Finalizers, FinalizerName) {
+		// This log line is printed exactly once during initial provisioning,
+		// because once the finalizer is in place this block gets skipped. So,
+		// this is a nice place to tell the operator that the high level,
+		// multi-reconcile operation is underway.
+		logger.Infof("exposing service over tailscale")
+		svc.Finalizers = append(svc.Finalizers, FinalizerName)
+		if err := a.Update(ctx, svc); err != nil {
+			return fmt.Errorf("failed to add finalizer: %w", err)
+		}
+	}
+	crl := childResourceLabels(svc)
+	var tags []string
+	if tstr, ok := svc.Annotations[AnnotationTags]; ok {
+		tags = strings.Split(tstr, ",")
+	}
+
+	sts := &tailscaleSTSConfig{
+		ParentResourceName:  svc.Name,
+		ParentResourceUID:   string(svc.UID),
+		TargetIP:            svc.Spec.ClusterIP,
+		Hostname:            hostname,
+		Tags:                tags,
+		ChildResourceLabels: crl,
+	}
+
+	if err := a.ssr.Provision(ctx, logger, sts); err != nil {
+		return fmt.Errorf("failed to provision: %w", err)
+	}
+
+	if !a.hasLoadBalancerClass(svc) {
+		logger.Debugf("service is not a LoadBalancer, so not updating ingress")
+		return nil
+	}
+
+	_, tsHost, err := a.ssr.DeviceInfo(ctx, crl)
+	if err != nil {
+		return fmt.Errorf("failed to get device ID: %w", err)
+	}
+	if tsHost == "" {
+		logger.Debugf("no Tailscale hostname known yet, waiting for proxy pod to finish auth")
+		// No hostname yet. Wait for the proxy pod to auth.
+		svc.Status.LoadBalancer.Ingress = nil
+		if err := a.Status().Update(ctx, svc); err != nil {
+			return fmt.Errorf("failed to update service status: %w", err)
+		}
+		return nil
+	}
+
+	logger.Debugf("setting ingress hostname to %q", tsHost)
+	svc.Status.LoadBalancer.Ingress = []corev1.LoadBalancerIngress{
+		{
+			Hostname: tsHost,
+		},
+	}
+	if err := a.Status().Update(ctx, svc); err != nil {
+		return fmt.Errorf("failed to update service status: %w", err)
+	}
+	return nil
+}
+
+func (a *ServiceReconciler) shouldExpose(svc *corev1.Service) bool {
+	// Headless services can't be exposed, since there is no ClusterIP to
+	// forward to.
+	if svc.Spec.ClusterIP == "" || svc.Spec.ClusterIP == "None" {
+		return false
+	}
+
+	return a.hasLoadBalancerClass(svc) || a.hasAnnotation(svc)
+}
+
+func (a *ServiceReconciler) hasLoadBalancerClass(svc *corev1.Service) bool {
+	return svc != nil &&
+		svc.Spec.Type == corev1.ServiceTypeLoadBalancer &&
+		svc.Spec.LoadBalancerClass != nil &&
+		*svc.Spec.LoadBalancerClass == "tailscale"
+}
+
+func (a *ServiceReconciler) hasAnnotation(svc *corev1.Service) bool {
+	return svc != nil &&
+		svc.Annotations[AnnotationExpose] == "true"
+}