Kubernetes Registry (#1064)

* add teh k8s registry

* add k8s reg config/cmd

* go mod update

util/kubernetes/client/watch.go

@@ -0,0 +1,122 @@
+package client
+
+import (
+	"bufio"
+	"context"
+	"encoding/json"
+	"errors"
+	"net/http"
+
+	"github.com/micro/go-micro/util/kubernetes/api"
+)
+
+const (
+	// EventTypes used
+	Added    EventType = "ADDED"
+	Modified EventType = "MODIFIED"
+	Deleted  EventType = "DELETED"
+	Error    EventType = "ERROR"
+)
+
+// Watcher is used to watch for events
+type Watcher interface {
+	// A channel of events
+	Chan() <-chan Event
+	// Stop the watcher
+	Stop()
+}
+
+// EventType defines the possible types of events.
+type EventType string
+
+// Event represents a single event to a watched resource.
+type Event struct {
+	Type   EventType       `json:"type"`
+	Object json.RawMessage `json:"object"`
+}
+
+// bodyWatcher scans the body of a request for chunks
+type bodyWatcher struct {
+	results chan Event
+	cancel  func()
+	stop    chan bool
+	res     *http.Response
+	req     *api.Request
+}
+
+// Changes returns the results channel
+func (wr *bodyWatcher) Chan() <-chan Event {
+	return wr.results
+}
+
+// Stop cancels the request
+func (wr *bodyWatcher) Stop() {
+	select {
+	case <-wr.stop:
+		return
+	default:
+		// cancel the request
+		wr.cancel()
+		// stop the watcher
+		close(wr.stop)
+	}
+}
+
+func (wr *bodyWatcher) stream() {
+	reader := bufio.NewReader(wr.res.Body)
+
+	go func() {
+		for {
+			// read a line
+			b, err := reader.ReadBytes('\n')
+			if err != nil {
+				return
+			}
+
+			// send the event
+			var event Event
+			if err := json.Unmarshal(b, &event); err != nil {
+				continue
+			}
+
+			select {
+			case <-wr.stop:
+				return
+			case wr.results <- event:
+			}
+		}
+	}()
+}
+
+// newWatcher creates a k8s body watcher for
+// a given http request
+func newWatcher(req *api.Request) (Watcher, error) {
+	// set request context so we can cancel the request
+	ctx, cancel := context.WithCancel(context.Background())
+	req.Context(ctx)
+
+	// do the raw request
+	res, err := req.Raw()
+	if err != nil {
+		return nil, err
+	}
+
+	if res.StatusCode < 200 || res.StatusCode >= 300 {
+		// close the response body
+		res.Body.Close()
+		// return an error
+		return nil, errors.New(res.Request.URL.String() + ": " + res.Status)
+	}
+
+	wr := &bodyWatcher{
+		results: make(chan Event),
+		stop:    make(chan bool),
+		cancel:  cancel,
+		req:     req,
+		res:     res,
+	}
+
+	go wr.stream()
+
+	return wr, nil
+}