kubectl-persistent-logger/logs/pod_watcher.go

241 lines
6.2 KiB
Go

package logs
import (
"bufio"
"context"
"errors"
"fmt"
"io"
"log"
"strings"
"sync"
"time"
corev1 "k8s.io/api/core/v1"
apierrors "k8s.io/apimachinery/pkg/api/errors"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/apimachinery/pkg/labels"
"k8s.io/apimachinery/pkg/watch"
)
const nl = "\n"
type stream struct {
podName string
namespace string
done chan struct{}
}
func newStream(podName, namespace string) stream {
return stream{podName: podName, namespace: namespace, done: make(chan struct{})}
}
func (s stream) close() {
close(s.done)
}
type streamError struct {
err error
stream stream
recoverable bool
}
func (re *streamError) Error() string {
return re.err.Error()
}
func newStreamError(err error, stream stream) *streamError {
return &streamError{err: err, stream: stream}
}
func newRecoverableError(err error, stream stream) *streamError {
return &streamError{err: err, stream: stream, recoverable: true}
}
// PodWatcher consumes and merges the logs for a specified set of pods.
type PodWatcher struct {
client KubernetesClient
namespace string
container string
labelSelector labels.Selector
spec map[string]*corev1.Pod
status map[string]stream
streamResults chan error
dst io.Writer
closeChan chan struct{}
logger *log.Logger
}
// NewPodWatcher initializes a new PodWatcher.
func NewPodWatcher(client KubernetesClient, namespace string, container string, labelSelector labels.Selector, dst io.Writer, logger *log.Logger) PodWatcherInterface {
return &PodWatcher{
client: client,
namespace: namespace,
container: container,
labelSelector: labelSelector,
spec: make(map[string]*corev1.Pod),
status: make(map[string]stream),
streamResults: make(chan error),
dst: dst,
closeChan: make(chan struct{}),
logger: logger,
}
}
// WatchPods blocks while it watches the pods which match the Selector of the
// provided deployment.
//
// Cancelling ctx will result in the event loop exiting immediately.
func (pw *PodWatcher) WatchPods(ctx context.Context) error {
var wg sync.WaitGroup
err := pw.watchPods(ctx, &wg)
wg.Wait()
pw.logger.Println("[PodWatcher] all goroutines exited, exiting")
return err
}
const tickerInterval = time.Millisecond * 250
// Close terminates the PodWatcher.
func (pw *PodWatcher) Close() {
close(pw.closeChan)
}
func (pw *PodWatcher) watchPods(ctx context.Context, wg *sync.WaitGroup) error {
podsClient := pw.client.Typed.CoreV1().Pods(pw.namespace)
// Returns a watcher which notifies of changes in the relevant pods.
// We don't defer Stop() on the returned value because the sender is the
// Kubernetes SDK, and that may introduce a send-on-closed-channel panic.
watcher, err := podsClient.Watch(ctx, metav1.ListOptions{LabelSelector: pw.labelSelector.String()})
if err != nil {
return err
}
ticker := time.NewTicker(tickerInterval)
defer ticker.Stop()
logStream := make(chan string)
streamErrors := make(chan error)
resultChan := watcher.ResultChan()
for {
select {
case <-ctx.Done():
return ctx.Err()
case <-pw.closeChan:
for _, stream := range pw.status {
stream.close()
}
return nil
case <-ticker.C:
// Iterate through the desired state (w.spec) and launch goroutines to
// process the logs of any missing pods.
for podName, pod := range pw.spec {
if _, ok := pw.status[podName]; !ok {
pw.logger.Printf("[PodWatcher] adding pod, name = %s", pod.Name)
s := newStream(pod.Name, pod.Namespace)
pw.status[pod.Name] = s
wg.Add(1)
go func() {
if err := copyPodLogs(ctx, wg, pw.client, s, pw.container, logStream); err != nil {
streamErrors <- err
}
}()
}
}
// For any pods which no longer exist, remove the pod.
for podName, stream := range pw.status {
if _, ok := pw.spec[podName]; !ok {
pw.removePod(stream)
}
}
// logStream is never closed
case l := <-logStream:
if _, err := pw.dst.Write([]byte(l)); err != nil {
return fmt.Errorf("error writing logs: %v", err)
}
// streamErrors is never closed
case err := <-streamErrors:
var streamErr *streamError
if errors.As(err, &streamErr) && streamErr.recoverable {
// if the error is recoverable, we just remove the pod from the status
// map. It will be recreated and retried on the next iteration.
pw.removePod(streamErr.stream)
} else {
return fmt.Errorf("error streaming logs: %w", streamErr)
}
case evt, ok := <-resultChan:
if !ok {
return nil
}
switch evt.Type {
case watch.Added, watch.Modified:
pod := evt.Object.(*corev1.Pod)
if pod.Status.Phase == corev1.PodRunning {
pw.spec[pod.Name] = pod
}
case watch.Deleted:
pod := evt.Object.(*corev1.Pod)
delete(pw.spec, pod.Name)
}
}
}
}
func (pw *PodWatcher) removePod(stream stream) {
pw.logger.Printf("[PodWatcher] removing pod, name = %s", stream.podName)
stream.close()
delete(pw.status, stream.podName)
}
func copyPodLogs(ctx context.Context, wg *sync.WaitGroup, client KubernetesClient, stream stream, container string, logStream chan string) error {
defer wg.Done()
req := client.Typed.CoreV1().Pods(stream.namespace).GetLogs(stream.podName, &corev1.PodLogOptions{Follow: true, Container: container})
logs, err := req.Stream(ctx)
// If one container is still being created, do not treat this as a fatal error.
var statusErr *apierrors.StatusError
if errors.As(err, &statusErr) && statusErr.Status().Reason == metav1.StatusReasonBadRequest && strings.Contains(statusErr.Error(), "ContainerCreating") {
return newRecoverableError(err, stream)
} else if err != nil {
return newStreamError(err, stream)
}
// Closing the reader ensures that the goroutine below is not leaked.
defer func() { _ = logs.Close() }()
done := make(chan error, 1)
go func() {
scanner := bufio.NewScanner(logs)
for scanner.Scan() {
logStream <- "[" + stream.podName + "] " + scanner.Text() + nl
}
if err := scanner.Err(); err != nil {
done <- newStreamError(fmt.Errorf("error scanning logs: %v", err), stream)
return
}
done <- nil
}()
for {
select {
case err := <-done:
return err
case <-stream.done:
return nil
case <-ctx.Done():
return ctx.Err()
}
}
}