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watch.go
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/
watch.go
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package k8s
import (
"bytes"
"context"
"encoding/binary"
"encoding/json"
"errors"
"fmt"
"io"
"io/ioutil"
metav1 "github.com/karlmutch/k8s/apis/meta/v1"
"github.com/karlmutch/k8s/runtime"
"github.com/golang/protobuf/proto"
)
// Decode events from a watch stream.
//
// See: https://github.com/kubernetes/community/blob/master/contributors/design-proposals/protobuf.md#streaming-wire-format
// Watcher receives a stream of events tracking a particular resource within
// a namespace or across all namespaces.
//
// Watcher does not automatically reconnect. If a watch fails, a new watch must
// be initialized.
type Watcher struct {
watcher interface {
Next(Resource) (string, error)
Close() error
}
}
// Next decodes the next event from the watch stream. Errors are fatal, and
// indicate that the watcher should no longer be used, and must be recreated.
func (w *Watcher) Next(r Resource) (string, error) {
return w.watcher.Next(r)
}
// Close closes the active connection with the API server being used for
// the watch.
func (w *Watcher) Close() error {
return w.watcher.Close()
}
type watcherJSON struct {
d *json.Decoder
c io.Closer
}
func (w *watcherJSON) Close() error {
return w.c.Close()
}
func (w *watcherJSON) Next(r Resource) (string, error) {
var event struct {
Type string `json:"type"`
Object json.RawMessage `json:"object"`
}
if err := w.d.Decode(&event); err != nil {
return "", fmt.Errorf("decode event: %v", err)
}
if event.Type == "" {
return "", errors.New("watch event had no type field")
}
if event.Type == EventError {
status := &metav1.Status{}
if err := json.Unmarshal([]byte(event.Object), status); err != nil {
return "", fmt.Errorf("decoding event error: %v", err)
}
return event.Type, &APIError{
Status: status,
Code: int(*status.Code),
}
}
if err := json.Unmarshal([]byte(event.Object), r); err != nil {
return "", fmt.Errorf("decode resource: %v", err)
}
return event.Type, nil
}
type watcherPB struct {
r io.ReadCloser
}
func (w *watcherPB) Next(r Resource) (string, error) {
msg, ok := r.(proto.Message)
if !ok {
return "", errors.New("object was not a protobuf message")
}
event, unknown, err := w.next()
if err != nil {
return "", err
}
if event.Type == nil || *event.Type == "" {
return "", errors.New("watch event had no type field")
}
if *event.Type == EventError {
status := &metav1.Status{}
if err := proto.Unmarshal(unknown.Raw, status); err != nil {
return "", fmt.Errorf("decoding event error: %v", err)
}
return *event.Type, &APIError{
Status: status,
Code: int(*status.Code),
}
}
if err := proto.Unmarshal(unknown.Raw, msg); err != nil {
return "", err
}
return *event.Type, nil
}
func (w *watcherPB) Close() error {
return w.r.Close()
}
func (w *watcherPB) next() (*metav1.WatchEvent, *runtime.Unknown, error) {
length := make([]byte, 4)
if _, err := io.ReadFull(w.r, length); err != nil {
return nil, nil, err
}
body := make([]byte, int(binary.BigEndian.Uint32(length)))
if _, err := io.ReadFull(w.r, body); err != nil {
return nil, nil, fmt.Errorf("read frame body: %v", err)
}
var event metav1.WatchEvent
if err := proto.Unmarshal(body, &event); err != nil {
return nil, nil, err
}
if event.Object == nil {
return nil, nil, fmt.Errorf("event had no underlying object")
}
unknown, err := parseUnknown(event.Object.Raw)
if err != nil {
return nil, nil, err
}
return &event, unknown, nil
}
var unknownPrefix = []byte{0x6b, 0x38, 0x73, 0x00}
func parseUnknown(b []byte) (*runtime.Unknown, error) {
if !bytes.HasPrefix(b, unknownPrefix) {
return nil, errors.New("bytes did not start with expected prefix")
}
var u runtime.Unknown
if err := proto.Unmarshal(b[len(unknownPrefix):], &u); err != nil {
return nil, err
}
return &u, nil
}
// Watch creates a watch on a resource. It takes an example Resource to
// determine what endpoint to watch.
//
// Watch does not automatically reconnect. If a watch fails, a new watch must
// be initialized.
//
// // Watch configmaps in the "kube-system" namespace
// var configMap corev1.ConfigMap
// watcher, err := client.Watch(ctx, "kube-system", &configMap)
// if err != nil {
// // handle error
// }
// defer watcher.Close() // Always close the returned watcher.
//
// for {
// cm := new(corev1.ConfigMap)
// eventType, err := watcher.Next(cm)
// if err != nil {
// // watcher encountered and error, exit or create a new watcher
// }
// fmt.Println(eventType, *cm.Metadata.Name)
// }
//
func (c *Client) Watch(ctx context.Context, namespace string, r Resource, options ...Option) (*Watcher, error) {
url, err := resourceWatchURL(c.Endpoint, namespace, r, options...)
if err != nil {
return nil, err
}
ct := contentTypeFor(r)
req, err := c.newRequest(ctx, "GET", url, nil)
if err != nil {
return nil, err
}
req.Header.Set("Accept", ct)
resp, err := c.client().Do(req)
if err != nil {
return nil, err
}
if resp.StatusCode/100 != 2 {
body, err := ioutil.ReadAll(resp.Body)
resp.Body.Close()
if err != nil {
return nil, err
}
return nil, newAPIError(resp.Header.Get("Content-Type"), resp.StatusCode, body)
}
if ct == contentTypePB {
return &Watcher{&watcherPB{r: resp.Body}}, nil
}
return &Watcher{&watcherJSON{
d: json.NewDecoder(resp.Body),
c: resp.Body,
}}, nil
}