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resolver_k8s.go
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resolver_k8s.go
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// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0
package loadbalancingexporter // import "github.com/open-telemetry/opentelemetry-collector-contrib/exporter/loadbalancingexporter"
import (
"context"
"errors"
"fmt"
"net"
"os"
"sort"
"strconv"
"strings"
"sync"
"go.opencensus.io/stats"
"go.opencensus.io/tag"
"go.uber.org/zap"
corev1 "k8s.io/api/core/v1"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/apimachinery/pkg/runtime"
"k8s.io/apimachinery/pkg/watch"
"k8s.io/client-go/kubernetes"
"k8s.io/client-go/tools/cache"
"k8s.io/utils/pointer"
"k8s.io/utils/strings/slices"
"sigs.k8s.io/controller-runtime/pkg/client/config"
)
var _ resolver = (*k8sResolver)(nil)
var (
errNoSvc = errors.New("no service specified to resolve the backends")
k8sResolverMutator = tag.Upsert(tag.MustNewKey("resolver"), "k8s")
k8sResolverSuccessTrueMutators = []tag.Mutator{k8sResolverMutator, successTrueMutator}
k8sResolverSuccessFalseMutators = []tag.Mutator{k8sResolverMutator, successFalseMutator}
)
type k8sResolver struct {
logger *zap.Logger
svcName string
svcNs string
port []int32
handler *handler
once *sync.Once
epsListWatcher cache.ListerWatcher
endpointsStore *sync.Map
endpoints []string
onChangeCallbacks []func([]string)
stopCh chan struct{}
updateLock sync.RWMutex
shutdownWg sync.WaitGroup
changeCallbackLock sync.RWMutex
}
func newK8sResolver(clt kubernetes.Interface,
logger *zap.Logger,
service string,
ports []int32) (*k8sResolver, error) {
if len(service) == 0 {
return nil, errNoSvc
}
nAddr := strings.SplitN(service, ".", 2)
name, namespace := nAddr[0], "default"
if len(nAddr) > 1 {
namespace = nAddr[1]
} else {
logger.Info("the namespace for the Kubernetes service wasn't provided, trying to determine the current namespace", zap.String("name", name))
if ns, err := getInClusterNamespace(); err == nil {
namespace = ns
logger.Info("namespace for the Collector determined", zap.String("namespace", namespace))
} else {
logger.Warn(`could not determine the namespace for this collector, will use "default" as the namespace`, zap.Error(err))
}
}
epsSelector := fmt.Sprintf("metadata.name=%s", name)
epsListWatcher := &cache.ListWatch{
ListFunc: func(options metav1.ListOptions) (runtime.Object, error) {
options.FieldSelector = epsSelector
options.TimeoutSeconds = pointer.Int64(1)
return clt.CoreV1().Endpoints(namespace).List(context.Background(), options)
},
WatchFunc: func(options metav1.ListOptions) (watch.Interface, error) {
options.FieldSelector = epsSelector
options.TimeoutSeconds = pointer.Int64(1)
return clt.CoreV1().Endpoints(namespace).Watch(context.Background(), options)
},
}
epsStore := &sync.Map{}
h := &handler{endpoints: epsStore, logger: logger}
r := &k8sResolver{
logger: logger,
svcName: name,
svcNs: namespace,
port: ports,
once: &sync.Once{},
endpointsStore: epsStore,
epsListWatcher: epsListWatcher,
handler: h,
stopCh: make(chan struct{}),
}
h.callback = r.resolve
return r, nil
}
func (r *k8sResolver) start(_ context.Context) error {
var initErr error
r.once.Do(func() {
if r.epsListWatcher != nil {
r.logger.Debug("creating and starting endpoints informer")
epsInformer := cache.NewSharedInformer(r.epsListWatcher, &corev1.Endpoints{}, 0)
if _, err := epsInformer.AddEventHandler(r.handler); err != nil {
r.logger.Error("unable to start watching for changes to the specified service names", zap.Error(err))
}
go epsInformer.Run(r.stopCh)
if !cache.WaitForCacheSync(r.stopCh, epsInformer.HasSynced) {
initErr = errors.New("endpoints informer not sync")
}
}
})
if initErr != nil {
return initErr
}
r.logger.Debug("K8s service resolver started",
zap.String("service", r.svcName),
zap.String("namespace", r.svcNs),
zap.Int32s("ports", r.port))
return nil
}
func (r *k8sResolver) shutdown(_ context.Context) error {
r.changeCallbackLock.Lock()
r.onChangeCallbacks = nil
r.changeCallbackLock.Unlock()
close(r.stopCh)
r.shutdownWg.Wait()
return nil
}
func newInClusterClient() (kubernetes.Interface, error) {
cfg, err := config.GetConfig()
if err != nil {
return nil, err
}
return kubernetes.NewForConfig(cfg)
}
func (r *k8sResolver) resolve(ctx context.Context) ([]string, error) {
r.shutdownWg.Add(1)
defer r.shutdownWg.Done()
var backends []string
r.endpointsStore.Range(func(address, value any) bool {
addr := address.(string)
if len(r.port) == 0 {
backends = append(backends, addr)
} else {
for _, port := range r.port {
backends = append(backends, net.JoinHostPort(addr, strconv.FormatInt(int64(port), 10)))
}
}
return true
})
_ = stats.RecordWithTags(ctx, k8sResolverSuccessTrueMutators, mNumResolutions.M(1))
// keep it always in the same order
sort.Strings(backends)
if slices.Equal(r.Endpoints(), backends) {
return r.Endpoints(), nil
}
// the list has changed!
r.updateLock.Lock()
r.endpoints = backends
r.updateLock.Unlock()
_ = stats.RecordWithTags(ctx, k8sResolverSuccessTrueMutators, mNumBackends.M(int64(len(backends))))
// propagate the change
r.changeCallbackLock.RLock()
for _, callback := range r.onChangeCallbacks {
callback(r.Endpoints())
}
r.changeCallbackLock.RUnlock()
return r.Endpoints(), nil
}
func (r *k8sResolver) onChange(f func([]string)) {
r.changeCallbackLock.Lock()
defer r.changeCallbackLock.Unlock()
r.onChangeCallbacks = append(r.onChangeCallbacks, f)
}
func (r *k8sResolver) Endpoints() []string {
r.updateLock.RLock()
defer r.updateLock.RUnlock()
return r.endpoints
}
const inClusterNamespacePath = "/var/run/secrets/kubernetes.io/serviceaccount/namespace"
func getInClusterNamespace() (string, error) {
// Check whether the namespace file exists.
// If not, we are not running in cluster so can't guess the namespace.
if _, err := os.Stat(inClusterNamespacePath); os.IsNotExist(err) {
return "", fmt.Errorf("not running in-cluster, please specify namespace")
} else if err != nil {
return "", fmt.Errorf("error checking namespace file: %w", err)
}
// Load the namespace file and return its content
namespace, err := os.ReadFile(inClusterNamespacePath)
if err != nil {
return "", fmt.Errorf("error reading namespace file: %w", err)
}
return string(namespace), nil
}