Add support for watch.

examples/watch/watch.go

@@ -0,0 +1,52 @@
+/*
+Copyright 2019 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Note: the example only works with the code within the same release/branch.
+package main
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/kubernetes-client/go/kubernetes/client"
+	"github.com/kubernetes-client/go/kubernetes/config"
+)
+
+func main() {
+	c, err := config.LoadKubeConfig()
+	if err != nil {
+		panic(err.Error())
+	}
+	cl := client.NewAPIClient(c)
+
+	watch := client.WatchClient{
+		Cfg:     c,
+		Client:  cl,
+		Path:    "/api/v1/namespaces",
+		MakerFn: func() interface{} { return &client.V1Namespace{} },
+	}
+	if resultChan, errChan, err := watch.Connect(context.Background()); err != nil {
+		panic(err)
+	} else {
+		for obj := range resultChan {
+			fmt.Printf("%s\n%#v\n", obj.Type, obj.Object)
+		}
+		for err := range errChan {
+			fmt.Printf("ERROR: %#v", err)
+		}
+		fmt.Printf("Closed!\n")
+	}
+}

kubernetes/client/watch.go

@@ -0,0 +1,98 @@
+package client
+
+import (
+	"bufio"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"strings"
+)
+
+// Result is a watch result
+type Result struct {
+	Type   string
+	Object interface{}
+}
+
+// WatchClient is a client for Watching the Kubernetes API
+type WatchClient struct {
+	Cfg     *Configuration
+	Client  *APIClient
+	Path    string
+	MakerFn func() interface{}
+}
+
+func (w *WatchClient) Connect(ctx context.Context) (<-chan *Result, <-chan error, error) {
+	url := w.Cfg.Scheme + "://" + w.Cfg.Host + w.Path + "?watch=true"
+	req, err := w.Client.prepareRequest(ctx, url, "GET", nil, nil, nil, nil, "", []byte{})
+	if err != nil {
+		return nil, nil, err
+	}
+	res, err := w.Client.callAPI(req)
+	if err != nil {
+		return nil, nil, err
+	}
+	if res.StatusCode != 200 {
+		return nil, nil, fmt.Errorf("Error connecting watch (%d: %s)", res.StatusCode, res.Status)
+	}
+	resultChan := make(chan *Result)
+	errChan := make(chan error)
+	processWatch(res.Body, w.MakerFn, resultChan, errChan)
+	return resultChan, errChan, nil
+}
+
+func processWatch(stream io.Reader, makerFn func() interface{}, resultChan chan<- *Result, errChan chan<- error) {
+	scanner := bufio.NewScanner(stream)
+	go func() {
+		defer close(resultChan)
+		defer close(errChan)
+		for scanner.Scan() {
+			watchObj, err := decode(scanner.Text(), makerFn)
+			if err != nil {
+				errChan <- err
+				return
+			}
+			if watchObj != nil {
+				resultChan <- watchObj
+			}
+		}
+		if err := scanner.Err(); err != nil {
+			errChan <- err
+		}
+	}()
+}
+
+func decode(line string, makerFn func() interface{}) (*Result, error) {
+	if len(line) == 0 {
+		return nil, nil
+	}
+	decoder := json.NewDecoder(strings.NewReader(line))
+	result := &Result{}
+	for decoder.More() {
+		name, err := decoder.Token()
+		if err != nil {
+			return nil, err
+		}
+		if name == "type" {
+			token, err := decoder.Token()
+			if err != nil {
+				return nil, err
+			}
+			var ok bool
+			result.Type, ok = token.(string)
+			if !ok {
+				return nil, fmt.Errorf("Error casting %v to string", token)
+			}
+		}
+		if name == "object" {
+			obj := makerFn()
+			if err := decoder.Decode(&obj); err != nil {
+				return nil, err
+			}
+			result.Object = obj
+			return result, nil
+		}
+	}
+	return nil, nil
+}

kubernetes/client/watch_test.go

@@ -0,0 +1,55 @@
+package client
+
+import (
+	"strings"
+	"testing"
+)
+
+func makerFn() interface{} { return &V1Namespace{} }
+
+func TestDecode(t *testing.T) {
+	line := `{"type":"ADDED","object":{"kind":"Namespace","apiVersion":"v1","metadata":{"name":"kube-system","selfLink":"/api/v1/namespaces/kube-system","uid":"164931a7-3d75-11e9-a0a0-2683b9459238","resourceVersion":"227","creationTimestamp":"2019-03-03T05:27:50Z","annotations":{"kubectl.kubernetes.io/last-applied-configuration":"{\"apiVersion\":\"v1\",\"kind\":\"Namespace\",\"metadata\":{\"annotations\":{},\"name\":\"kube-system\",\"namespace\":\"\"}}\n"}},"spec":{"finalizers":["kubernetes"]},"status":{"phase":"Active"}}}`
+	result, err := decode(line, makerFn)
+	if err != nil {
+		t.Errorf("Unexpeceted non-nil: %v", err)
+	}
+	ns, ok := result.Object.(*V1Namespace)
+	if !ok {
+		t.Errorf("Cast failed: %v", result.Object)
+	}
+	if ns.Kind != "Namespace" || ns.Metadata.Name != "kube-system" {
+		t.Errorf("Unexpected value %#v", *ns)
+	}
+}
+
+func TestMultiDecode(t *testing.T) {
+	lines := `
+	{"type":"ADDED","object":{"kind":"Namespace","apiVersion":"v1","metadata":{"name":"kube-system","selfLink":"/api/v1/namespaces/kube-system","uid":"164931a7-3d75-11e9-a0a0-2683b9459238","resourceVersion":"227","creationTimestamp":"2019-03-03T05:27:50Z","annotations":{"kubectl.kubernetes.io/last-applied-configuration":"{\"apiVersion\":\"v1\",\"kind\":\"Namespace\",\"metadata\":{\"annotations\":{},\"name\":\"kube-system\",\"namespace\":\"\"}}\n"}},"spec":{"finalizers":["kubernetes"]},"status":{"phase":"Active"}}}
+	{"type":"MODIFIED","object":{"kind":"Namespace","apiVersion":"v1","metadata":{"name":"kube-system-2","selfLink":"/api/v1/namespaces/kube-system","uid":"164931a7-3d75-11e9-a0a0-2683b9459238","resourceVersion":"227","creationTimestamp":"2019-03-03T05:27:50Z","annotations":{"kubectl.kubernetes.io/last-applied-configuration":"{\"apiVersion\":\"v1\",\"kind\":\"Namespace\",\"metadata\":{\"annotations\":{},\"name\":\"kube-system\",\"namespace\":\"\"}}\n"}},"spec":{"finalizers":["kubernetes"]},"status":{"phase":"Active"}}}
+	{"type":"DELETED","object":{"kind":"Namespace","apiVersion":"v1","metadata":{"name":"kube-system-3","selfLink":"/api/v1/namespaces/kube-system","uid":"164931a7-3d75-11e9-a0a0-2683b9459238","resourceVersion":"227","creationTimestamp":"2019-03-03T05:27:50Z","annotations":{"kubectl.kubernetes.io/last-applied-configuration":"{\"apiVersion\":\"v1\",\"kind\":\"Namespace\",\"metadata\":{\"annotations\":{},\"name\":\"kube-system\",\"namespace\":\"\"}}\n"}},"spec":{"finalizers":["kubernetes"]},"status":{"phase":"Active"}}}
+	`
+
+	results := make(chan *Result)
+	errs := make(chan error)
+	processWatch(strings.NewReader(lines), makerFn, results, errs)
+
+	out := []*Result{}
+	outErrs := []error{}
+
+	for r := range results {
+		out = append(out, r)
+	}
+
+	for e := range errs {
+		outErrs = append(outErrs, e)
+	}
+
+	if len(out) != 3 {
+		t.Errorf("unexpected results: %v", out)
+	}
+	for ix, val := range []string{"ADDED", "MODIFIED", "DELETED"} {
+		if out[ix].Type != val {
+			t.Errorf("unexpected value (%d): %v", ix, out[ix])
+		}
+	}
+}