traefik/pkg/provider/kubernetes/ingress/kubernetes.go
2023-07-19 17:36:06 +02:00

751 lines
24 KiB
Go

package ingress
import (
"context"
"crypto/sha256"
"errors"
"fmt"
"math"
"net"
"os"
"sort"
"strconv"
"strings"
"time"
"github.com/cenkalti/backoff/v4"
"github.com/mitchellh/hashstructure"
ptypes "github.com/traefik/paerser/types"
"github.com/traefik/traefik/v2/pkg/config/dynamic"
"github.com/traefik/traefik/v2/pkg/job"
"github.com/traefik/traefik/v2/pkg/log"
"github.com/traefik/traefik/v2/pkg/provider"
"github.com/traefik/traefik/v2/pkg/provider/kubernetes/k8s"
"github.com/traefik/traefik/v2/pkg/safe"
"github.com/traefik/traefik/v2/pkg/tls"
corev1 "k8s.io/api/core/v1"
netv1 "k8s.io/api/networking/v1"
"k8s.io/apimachinery/pkg/labels"
)
const (
annotationKubernetesIngressClass = "kubernetes.io/ingress.class"
traefikDefaultIngressClass = "traefik"
traefikDefaultIngressClassController = "traefik.io/ingress-controller"
defaultPathMatcher = "PathPrefix"
)
// Provider holds configurations of the provider.
type Provider struct {
Endpoint string `description:"Kubernetes server endpoint (required for external cluster client)." json:"endpoint,omitempty" toml:"endpoint,omitempty" yaml:"endpoint,omitempty"`
Token string `description:"Kubernetes bearer token (not needed for in-cluster client)." json:"token,omitempty" toml:"token,omitempty" yaml:"token,omitempty" loggable:"false"`
CertAuthFilePath string `description:"Kubernetes certificate authority file path (not needed for in-cluster client)." json:"certAuthFilePath,omitempty" toml:"certAuthFilePath,omitempty" yaml:"certAuthFilePath,omitempty"`
Namespaces []string `description:"Kubernetes namespaces." json:"namespaces,omitempty" toml:"namespaces,omitempty" yaml:"namespaces,omitempty" export:"true"`
LabelSelector string `description:"Kubernetes Ingress label selector to use." json:"labelSelector,omitempty" toml:"labelSelector,omitempty" yaml:"labelSelector,omitempty" export:"true"`
IngressClass string `description:"Value of kubernetes.io/ingress.class annotation or IngressClass name to watch for." json:"ingressClass,omitempty" toml:"ingressClass,omitempty" yaml:"ingressClass,omitempty" export:"true"`
IngressEndpoint *EndpointIngress `description:"Kubernetes Ingress Endpoint." json:"ingressEndpoint,omitempty" toml:"ingressEndpoint,omitempty" yaml:"ingressEndpoint,omitempty" export:"true"`
ThrottleDuration ptypes.Duration `description:"Ingress refresh throttle duration" json:"throttleDuration,omitempty" toml:"throttleDuration,omitempty" yaml:"throttleDuration,omitempty" export:"true"`
AllowEmptyServices bool `description:"Allow creation of services without endpoints." json:"allowEmptyServices,omitempty" toml:"allowEmptyServices,omitempty" yaml:"allowEmptyServices,omitempty" export:"true"`
AllowExternalNameServices bool `description:"Allow ExternalName services." json:"allowExternalNameServices,omitempty" toml:"allowExternalNameServices,omitempty" yaml:"allowExternalNameServices,omitempty" export:"true"`
lastConfiguration safe.Safe
routerTransform k8s.RouterTransform
}
func (p *Provider) SetRouterTransform(routerTransform k8s.RouterTransform) {
p.routerTransform = routerTransform
}
func (p *Provider) applyRouterTransform(ctx context.Context, rt *dynamic.Router, ingress *netv1.Ingress) {
if p.routerTransform == nil {
return
}
err := p.routerTransform.Apply(ctx, rt, ingress.Annotations)
if err != nil {
log.FromContext(ctx).WithError(err).Error("Apply router transform")
}
}
// EndpointIngress holds the endpoint information for the Kubernetes provider.
type EndpointIngress struct {
IP string `description:"IP used for Kubernetes Ingress endpoints." json:"ip,omitempty" toml:"ip,omitempty" yaml:"ip,omitempty"`
Hostname string `description:"Hostname used for Kubernetes Ingress endpoints." json:"hostname,omitempty" toml:"hostname,omitempty" yaml:"hostname,omitempty"`
PublishedService string `description:"Published Kubernetes Service to copy status from." json:"publishedService,omitempty" toml:"publishedService,omitempty" yaml:"publishedService,omitempty"`
}
func (p *Provider) newK8sClient(ctx context.Context) (*clientWrapper, error) {
_, err := labels.Parse(p.LabelSelector)
if err != nil {
return nil, fmt.Errorf("invalid ingress label selector: %q", p.LabelSelector)
}
logger := log.FromContext(ctx)
logger.Infof("ingress label selector is: %q", p.LabelSelector)
withEndpoint := ""
if p.Endpoint != "" {
withEndpoint = fmt.Sprintf(" with endpoint %v", p.Endpoint)
}
var cl *clientWrapper
switch {
case os.Getenv("KUBERNETES_SERVICE_HOST") != "" && os.Getenv("KUBERNETES_SERVICE_PORT") != "":
logger.Infof("Creating in-cluster Provider client%s", withEndpoint)
cl, err = newInClusterClient(p.Endpoint)
case os.Getenv("KUBECONFIG") != "":
logger.Infof("Creating cluster-external Provider client from KUBECONFIG %s", os.Getenv("KUBECONFIG"))
cl, err = newExternalClusterClientFromFile(os.Getenv("KUBECONFIG"))
default:
logger.Infof("Creating cluster-external Provider client%s", withEndpoint)
cl, err = newExternalClusterClient(p.Endpoint, p.Token, p.CertAuthFilePath)
}
if err != nil {
return nil, err
}
cl.ingressLabelSelector = p.LabelSelector
return cl, nil
}
// Init the provider.
func (p *Provider) Init() error {
return nil
}
// Provide allows the k8s provider to provide configurations to traefik
// using the given configuration channel.
func (p *Provider) Provide(configurationChan chan<- dynamic.Message, pool *safe.Pool) error {
ctxLog := log.With(context.Background(), log.Str(log.ProviderName, "kubernetes"))
logger := log.FromContext(ctxLog)
k8sClient, err := p.newK8sClient(ctxLog)
if err != nil {
return err
}
if p.AllowExternalNameServices {
logger.Warn("ExternalName service loading is enabled, please ensure that this is expected (see AllowExternalNameServices option)")
}
pool.GoCtx(func(ctxPool context.Context) {
operation := func() error {
eventsChan, err := k8sClient.WatchAll(p.Namespaces, ctxPool.Done())
if err != nil {
logger.Errorf("Error watching kubernetes events: %v", err)
timer := time.NewTimer(1 * time.Second)
select {
case <-timer.C:
return err
case <-ctxPool.Done():
return nil
}
}
throttleDuration := time.Duration(p.ThrottleDuration)
throttledChan := throttleEvents(ctxLog, throttleDuration, pool, eventsChan)
if throttledChan != nil {
eventsChan = throttledChan
}
for {
select {
case <-ctxPool.Done():
return nil
case event := <-eventsChan:
// Note that event is the *first* event that came in during this
// throttling interval -- if we're hitting our throttle, we may have
// dropped events. This is fine, because we don't treat different
// event types differently. But if we do in the future, we'll need to
// track more information about the dropped events.
conf := p.loadConfigurationFromIngresses(ctxLog, k8sClient)
confHash, err := hashstructure.Hash(conf, nil)
switch {
case err != nil:
logger.Error("Unable to hash the configuration")
case p.lastConfiguration.Get() == confHash:
logger.Debugf("Skipping Kubernetes event kind %T", event)
default:
p.lastConfiguration.Set(confHash)
configurationChan <- dynamic.Message{
ProviderName: "kubernetes",
Configuration: conf,
}
}
// If we're throttling, we sleep here for the throttle duration to
// enforce that we don't refresh faster than our throttle. time.Sleep
// returns immediately if p.ThrottleDuration is 0 (no throttle).
time.Sleep(throttleDuration)
}
}
}
notify := func(err error, time time.Duration) {
logger.Errorf("Provider connection error: %s; retrying in %s", err, time)
}
err := backoff.RetryNotify(safe.OperationWithRecover(operation), backoff.WithContext(job.NewBackOff(backoff.NewExponentialBackOff()), ctxPool), notify)
if err != nil {
logger.Errorf("Cannot connect to Provider: %s", err)
}
})
return nil
}
func (p *Provider) loadConfigurationFromIngresses(ctx context.Context, client Client) *dynamic.Configuration {
conf := &dynamic.Configuration{
HTTP: &dynamic.HTTPConfiguration{
Routers: map[string]*dynamic.Router{},
Middlewares: map[string]*dynamic.Middleware{},
Services: map[string]*dynamic.Service{},
},
TCP: &dynamic.TCPConfiguration{},
}
serverVersion := client.GetServerVersion()
var ingressClasses []*netv1.IngressClass
if supportsIngressClass(serverVersion) {
ics, err := client.GetIngressClasses()
if err != nil {
log.FromContext(ctx).Warnf("Failed to list ingress classes: %v", err)
}
if p.IngressClass != "" {
ingressClasses = filterIngressClassByName(p.IngressClass, ics)
} else {
ingressClasses = ics
}
}
ingresses := client.GetIngresses()
certConfigs := make(map[string]*tls.CertAndStores)
for _, ingress := range ingresses {
ctx = log.With(ctx, log.Str("ingress", ingress.Name), log.Str("namespace", ingress.Namespace))
if !p.shouldProcessIngress(ingress, ingressClasses) {
continue
}
rtConfig, err := parseRouterConfig(ingress.Annotations)
if err != nil {
log.FromContext(ctx).Errorf("Failed to parse annotations: %v", err)
continue
}
err = getCertificates(ctx, ingress, client, certConfigs)
if err != nil {
log.FromContext(ctx).Errorf("Error configuring TLS: %v", err)
}
if len(ingress.Spec.Rules) == 0 && ingress.Spec.DefaultBackend != nil {
if _, ok := conf.HTTP.Services["default-backend"]; ok {
log.FromContext(ctx).Error("The default backend already exists.")
continue
}
service, err := p.loadService(client, ingress.Namespace, *ingress.Spec.DefaultBackend)
if err != nil {
log.FromContext(ctx).
WithField("serviceName", ingress.Spec.DefaultBackend.Service.Name).
WithField("servicePort", ingress.Spec.DefaultBackend.Service.Port.String()).
Errorf("Cannot create service: %v", err)
continue
}
if len(service.LoadBalancer.Servers) == 0 && !p.AllowEmptyServices {
log.FromContext(ctx).
WithField("serviceName", ingress.Spec.DefaultBackend.Service.Name).
WithField("servicePort", ingress.Spec.DefaultBackend.Service.Port.String()).
Errorf("Skipping service: no endpoints found")
continue
}
rt := &dynamic.Router{
Rule: "PathPrefix(`/`)",
Priority: math.MinInt32,
Service: "default-backend",
}
if rtConfig != nil && rtConfig.Router != nil {
rt.EntryPoints = rtConfig.Router.EntryPoints
rt.Middlewares = rtConfig.Router.Middlewares
rt.TLS = rtConfig.Router.TLS
}
p.applyRouterTransform(ctx, rt, ingress)
conf.HTTP.Routers["default-router"] = rt
conf.HTTP.Services["default-backend"] = service
}
routers := map[string][]*dynamic.Router{}
for _, rule := range ingress.Spec.Rules {
if err := p.updateIngressStatus(ingress, client); err != nil {
log.FromContext(ctx).Errorf("Error while updating ingress status: %v", err)
}
if rule.HTTP == nil {
continue
}
for _, pa := range rule.HTTP.Paths {
service, err := p.loadService(client, ingress.Namespace, pa.Backend)
if err != nil {
log.FromContext(ctx).
WithField("serviceName", pa.Backend.Service.Name).
WithField("servicePort", pa.Backend.Service.Port.String()).
Errorf("Cannot create service: %v", err)
continue
}
if len(service.LoadBalancer.Servers) == 0 && !p.AllowEmptyServices {
log.FromContext(ctx).
WithField("serviceName", pa.Backend.Service.Name).
WithField("servicePort", pa.Backend.Service.Port.String()).
Errorf("Skipping service: no endpoints found")
continue
}
portString := pa.Backend.Service.Port.Name
if len(pa.Backend.Service.Port.Name) == 0 {
portString = fmt.Sprint(pa.Backend.Service.Port.Number)
}
serviceName := provider.Normalize(ingress.Namespace + "-" + pa.Backend.Service.Name + "-" + portString)
conf.HTTP.Services[serviceName] = service
rt := loadRouter(rule, pa, rtConfig, serviceName)
p.applyRouterTransform(ctx, rt, ingress)
routerKey := strings.TrimPrefix(provider.Normalize(ingress.Namespace+"-"+ingress.Name+"-"+rule.Host+pa.Path), "-")
routers[routerKey] = append(routers[routerKey], rt)
}
}
for routerKey, conflictingRouters := range routers {
if len(conflictingRouters) == 1 {
conf.HTTP.Routers[routerKey] = conflictingRouters[0]
continue
}
log.FromContext(ctx).Debugf("Multiple routers are defined with the same key %q, generating hashes to avoid conflicts", routerKey)
for _, router := range conflictingRouters {
key, err := makeRouterKeyWithHash(routerKey, router.Rule)
if err != nil {
log.FromContext(ctx).Error(err)
continue
}
conf.HTTP.Routers[key] = router
}
}
}
certs := getTLSConfig(certConfigs)
if len(certs) > 0 {
conf.TLS = &dynamic.TLSConfiguration{
Certificates: certs,
}
}
return conf
}
func (p *Provider) updateIngressStatus(ing *netv1.Ingress, k8sClient Client) error {
// Only process if an EndpointIngress has been configured.
if p.IngressEndpoint == nil {
return nil
}
if len(p.IngressEndpoint.PublishedService) == 0 {
if len(p.IngressEndpoint.IP) == 0 && len(p.IngressEndpoint.Hostname) == 0 {
return errors.New("publishedService or ip or hostname must be defined")
}
return k8sClient.UpdateIngressStatus(ing, []netv1.IngressLoadBalancerIngress{{IP: p.IngressEndpoint.IP, Hostname: p.IngressEndpoint.Hostname}})
}
serviceInfo := strings.Split(p.IngressEndpoint.PublishedService, "/")
if len(serviceInfo) != 2 {
return fmt.Errorf("invalid publishedService format (expected 'namespace/service' format): %s", p.IngressEndpoint.PublishedService)
}
serviceNamespace, serviceName := serviceInfo[0], serviceInfo[1]
service, exists, err := k8sClient.GetService(serviceNamespace, serviceName)
if err != nil {
return fmt.Errorf("cannot get service %s, received error: %w", p.IngressEndpoint.PublishedService, err)
}
if exists && service.Status.LoadBalancer.Ingress == nil {
// service exists, but has no Load Balancer status
log.Debugf("Skipping updating Ingress %s/%s due to service %s having no status set", ing.Namespace, ing.Name, p.IngressEndpoint.PublishedService)
return nil
}
if !exists {
return fmt.Errorf("missing service: %s", p.IngressEndpoint.PublishedService)
}
ingresses, err := convertSlice[netv1.IngressLoadBalancerIngress](service.Status.LoadBalancer.Ingress)
if err != nil {
return err
}
return k8sClient.UpdateIngressStatus(ing, ingresses)
}
func (p *Provider) shouldProcessIngress(ingress *netv1.Ingress, ingressClasses []*netv1.IngressClass) bool {
// configuration through the new kubernetes ingressClass
if ingress.Spec.IngressClassName != nil {
for _, ic := range ingressClasses {
if *ingress.Spec.IngressClassName == ic.ObjectMeta.Name {
return true
}
}
return false
}
return p.IngressClass == ingress.Annotations[annotationKubernetesIngressClass] ||
len(p.IngressClass) == 0 && ingress.Annotations[annotationKubernetesIngressClass] == traefikDefaultIngressClass
}
func buildHostRule(host string) string {
if strings.HasPrefix(host, "*.") {
return "HostRegexp(`" + strings.Replace(host, "*.", "{subdomain:[a-zA-Z0-9-]+}.", 1) + "`)"
}
return "Host(`" + host + "`)"
}
func getCertificates(ctx context.Context, ingress *netv1.Ingress, k8sClient Client, tlsConfigs map[string]*tls.CertAndStores) error {
for _, t := range ingress.Spec.TLS {
if t.SecretName == "" {
log.FromContext(ctx).Debugf("Skipping TLS sub-section: No secret name provided")
continue
}
configKey := ingress.Namespace + "-" + t.SecretName
if _, tlsExists := tlsConfigs[configKey]; !tlsExists {
secret, exists, err := k8sClient.GetSecret(ingress.Namespace, t.SecretName)
if err != nil {
return fmt.Errorf("failed to fetch secret %s/%s: %w", ingress.Namespace, t.SecretName, err)
}
if !exists {
return fmt.Errorf("secret %s/%s does not exist", ingress.Namespace, t.SecretName)
}
cert, key, err := getCertificateBlocks(secret, ingress.Namespace, t.SecretName)
if err != nil {
return err
}
tlsConfigs[configKey] = &tls.CertAndStores{
Certificate: tls.Certificate{
CertFile: tls.FileOrContent(cert),
KeyFile: tls.FileOrContent(key),
},
}
}
}
return nil
}
func getCertificateBlocks(secret *corev1.Secret, namespace, secretName string) (string, string, error) {
var missingEntries []string
tlsCrtData, tlsCrtExists := secret.Data["tls.crt"]
if !tlsCrtExists {
missingEntries = append(missingEntries, "tls.crt")
}
tlsKeyData, tlsKeyExists := secret.Data["tls.key"]
if !tlsKeyExists {
missingEntries = append(missingEntries, "tls.key")
}
if len(missingEntries) > 0 {
return "", "", fmt.Errorf("secret %s/%s is missing the following TLS data entries: %s",
namespace, secretName, strings.Join(missingEntries, ", "))
}
cert := string(tlsCrtData)
if cert == "" {
missingEntries = append(missingEntries, "tls.crt")
}
key := string(tlsKeyData)
if key == "" {
missingEntries = append(missingEntries, "tls.key")
}
if len(missingEntries) > 0 {
return "", "", fmt.Errorf("secret %s/%s contains the following empty TLS data entries: %s",
namespace, secretName, strings.Join(missingEntries, ", "))
}
return cert, key, nil
}
func getTLSConfig(tlsConfigs map[string]*tls.CertAndStores) []*tls.CertAndStores {
var secretNames []string
for secretName := range tlsConfigs {
secretNames = append(secretNames, secretName)
}
sort.Strings(secretNames)
var configs []*tls.CertAndStores
for _, secretName := range secretNames {
configs = append(configs, tlsConfigs[secretName])
}
return configs
}
func (p *Provider) loadService(client Client, namespace string, backend netv1.IngressBackend) (*dynamic.Service, error) {
if backend.Resource != nil {
// https://kubernetes.io/docs/concepts/services-networking/ingress/#resource-backend
return nil, errors.New("resource backends are not supported")
}
if backend.Service == nil {
return nil, errors.New("missing service definition")
}
service, exists, err := client.GetService(namespace, backend.Service.Name)
if err != nil {
return nil, err
}
if !exists {
return nil, errors.New("service not found")
}
if !p.AllowExternalNameServices && service.Spec.Type == corev1.ServiceTypeExternalName {
return nil, fmt.Errorf("externalName services not allowed: %s/%s", namespace, backend.Service.Name)
}
var portName string
var portSpec corev1.ServicePort
var match bool
for _, p := range service.Spec.Ports {
if backend.Service.Port.Number == p.Port || (backend.Service.Port.Name == p.Name && len(p.Name) > 0) {
portName = p.Name
portSpec = p
match = true
break
}
}
if !match {
return nil, errors.New("service port not found")
}
svc := &dynamic.Service{
LoadBalancer: &dynamic.ServersLoadBalancer{
PassHostHeader: func(v bool) *bool { return &v }(true),
},
}
svcConfig, err := parseServiceConfig(service.Annotations)
if err != nil {
return nil, err
}
if svcConfig != nil && svcConfig.Service != nil {
svc.LoadBalancer.Sticky = svcConfig.Service.Sticky
if svcConfig.Service.PassHostHeader != nil {
svc.LoadBalancer.PassHostHeader = svcConfig.Service.PassHostHeader
}
if svcConfig.Service.ServersTransport != "" {
svc.LoadBalancer.ServersTransport = svcConfig.Service.ServersTransport
}
if svcConfig.Service.NativeLB {
address, err := getNativeServiceAddress(*service, portSpec)
if err != nil {
return nil, fmt.Errorf("getting native Kubernetes Service address: %w", err)
}
protocol := getProtocol(portSpec, portSpec.Name, svcConfig)
svc.LoadBalancer.Servers = []dynamic.Server{
{URL: fmt.Sprintf("%s://%s", protocol, address)},
}
return svc, nil
}
}
if service.Spec.Type == corev1.ServiceTypeExternalName {
protocol := getProtocol(portSpec, portSpec.Name, svcConfig)
hostPort := net.JoinHostPort(service.Spec.ExternalName, strconv.Itoa(int(portSpec.Port)))
svc.LoadBalancer.Servers = []dynamic.Server{
{URL: fmt.Sprintf("%s://%s", protocol, hostPort)},
}
return svc, nil
}
endpoints, endpointsExists, endpointsErr := client.GetEndpoints(namespace, backend.Service.Name)
if endpointsErr != nil {
return nil, endpointsErr
}
if !endpointsExists {
return nil, errors.New("endpoints not found")
}
for _, subset := range endpoints.Subsets {
var port int32
for _, p := range subset.Ports {
if portName == p.Name {
port = p.Port
break
}
}
if port == 0 {
continue
}
protocol := getProtocol(portSpec, portName, svcConfig)
for _, addr := range subset.Addresses {
hostPort := net.JoinHostPort(addr.IP, strconv.Itoa(int(port)))
svc.LoadBalancer.Servers = append(svc.LoadBalancer.Servers, dynamic.Server{
URL: fmt.Sprintf("%s://%s", protocol, hostPort),
})
}
}
return svc, nil
}
func getNativeServiceAddress(service corev1.Service, svcPort corev1.ServicePort) (string, error) {
if service.Spec.ClusterIP == "None" {
return "", fmt.Errorf("no clusterIP on headless service: %s/%s", service.Namespace, service.Name)
}
if service.Spec.ClusterIP == "" {
return "", fmt.Errorf("no clusterIP found for service: %s/%s", service.Namespace, service.Name)
}
return net.JoinHostPort(service.Spec.ClusterIP, strconv.Itoa(int(svcPort.Port))), nil
}
func getProtocol(portSpec corev1.ServicePort, portName string, svcConfig *ServiceConfig) string {
if svcConfig != nil && svcConfig.Service != nil && svcConfig.Service.ServersScheme != "" {
return svcConfig.Service.ServersScheme
}
protocol := "http"
if portSpec.Port == 443 || strings.HasPrefix(portName, "https") {
protocol = "https"
}
return protocol
}
func makeRouterKeyWithHash(key, rule string) (string, error) {
h := sha256.New()
if _, err := h.Write([]byte(rule)); err != nil {
return "", err
}
dupKey := fmt.Sprintf("%s-%.10x", key, h.Sum(nil))
return dupKey, nil
}
func loadRouter(rule netv1.IngressRule, pa netv1.HTTPIngressPath, rtConfig *RouterConfig, serviceName string) *dynamic.Router {
var rules []string
if len(rule.Host) > 0 {
rules = []string{buildHostRule(rule.Host)}
}
if len(pa.Path) > 0 {
matcher := defaultPathMatcher
if pa.PathType == nil || *pa.PathType == "" || *pa.PathType == netv1.PathTypeImplementationSpecific {
if rtConfig != nil && rtConfig.Router != nil && rtConfig.Router.PathMatcher != "" {
matcher = rtConfig.Router.PathMatcher
}
} else if *pa.PathType == netv1.PathTypeExact {
matcher = "Path"
}
rules = append(rules, fmt.Sprintf("%s(`%s`)", matcher, pa.Path))
}
rt := &dynamic.Router{
Rule: strings.Join(rules, " && "),
Service: serviceName,
}
if rtConfig != nil && rtConfig.Router != nil {
rt.Priority = rtConfig.Router.Priority
rt.EntryPoints = rtConfig.Router.EntryPoints
rt.Middlewares = rtConfig.Router.Middlewares
if rtConfig.Router.TLS != nil {
rt.TLS = rtConfig.Router.TLS
}
}
return rt
}
func throttleEvents(ctx context.Context, throttleDuration time.Duration, pool *safe.Pool, eventsChan <-chan interface{}) chan interface{} {
if throttleDuration == 0 {
return nil
}
// Create a buffered channel to hold the pending event (if we're delaying processing the event due to throttling).
eventsChanBuffered := make(chan interface{}, 1)
// Run a goroutine that reads events from eventChan and does a
// non-blocking write to pendingEvent. This guarantees that writing to
// eventChan will never block, and that pendingEvent will have
// something in it if there's been an event since we read from that channel.
pool.GoCtx(func(ctxPool context.Context) {
for {
select {
case <-ctxPool.Done():
return
case nextEvent := <-eventsChan:
select {
case eventsChanBuffered <- nextEvent:
default:
// We already have an event in eventsChanBuffered, so we'll
// do a refresh as soon as our throttle allows us to. It's fine
// to drop the event and keep whatever's in the buffer -- we
// don't do different things for different events.
log.FromContext(ctx).Debugf("Dropping event kind %T due to throttling", nextEvent)
}
}
}
})
return eventsChanBuffered
}