[WIP] K8s update and runtime package changes (#895)

* First commit: outline of K8s runtime package

* Added poller. Added auto-updater into default runtime

* Added build and updated Poller interface

* Added comments and NewRuntime that accepts Options

* DefaultPoller; Runtime options

* First commit to add Kubernetes cruft

* Add comments

* Add micro- prefix to K8s runtime service names

* Get rid of import cycles. Move K8s runtime into main runtime package

* Major refactoring: Poller replaced by Notifier

POller has been replaced by Notifier which returns a channel of events
that can be consumed and acted upon.

* Added runtime configuration options

* K8s runtime is now Kubernetes runtime in dedicated pkg. Naming kung-fu.

* Fix typo in command.

* Fixed typo

* Dont Delete service when runtime stops.

runtime.Stop stops services; no need to double-stop

* Track runtime services

* Parse Unix timestamps properly

* Added deployments into K8s client. Debug logging

runtime/kubernetes/client/client.go

@@ -0,0 +1,102 @@
+package client
+
+import (
+	"crypto/tls"
+	"errors"
+	"io/ioutil"
+	"net/http"
+	"os"
+	"path"
+
+	"github.com/micro/go-micro/runtime/kubernetes/client/api"
+	"github.com/micro/go-micro/util/log"
+)
+
+var (
+	serviceAccountPath = "/var/run/secrets/kubernetes.io/serviceaccount"
+	// ErrReadNamespace is returned when the names could not be read from service account
+	ErrReadNamespace = errors.New("Could not read namespace from service account secret")
+)
+
+// Client ...
+type client struct {
+	opts *api.Options
+}
+
+// NewClientInCluster should work similarily to the official api
+// NewInClient by setting up a client configuration for use within
+// a k8s pod.
+func NewClientInCluster() *client {
+	host := "https://" + os.Getenv("KUBERNETES_SERVICE_HOST") + ":" + os.Getenv("KUBERNETES_SERVICE_PORT")
+
+	s, err := os.Stat(serviceAccountPath)
+	if err != nil {
+		log.Fatal(err)
+	}
+	if s == nil || !s.IsDir() {
+		log.Fatal(errors.New("no k8s service account found"))
+	}
+
+	token, err := ioutil.ReadFile(path.Join(serviceAccountPath, "token"))
+	if err != nil {
+		log.Fatal(err)
+	}
+	t := string(token)
+
+	ns, err := detectNamespace()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	crt, err := CertPoolFromFile(path.Join(serviceAccountPath, "ca.crt"))
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	c := &http.Client{
+		Transport: &http.Transport{
+			TLSClientConfig: &tls.Config{
+				RootCAs: crt,
+			},
+			DisableCompression: true,
+		},
+	}
+
+	return &client{
+		opts: &api.Options{
+			Client:      c,
+			Host:        host,
+			Namespace:   ns,
+			BearerToken: &t,
+		},
+	}
+}
+
+func detectNamespace() (string, error) {
+	nsPath := path.Join(serviceAccountPath, "namespace")
+
+	// Make sure it's a file and we can read it
+	if s, e := os.Stat(nsPath); e != nil {
+		return "", e
+	} else if s.IsDir() {
+		return "", ErrReadNamespace
+	}
+
+	// Read the file, and cast to a string
+	if ns, e := ioutil.ReadFile(nsPath); e != nil {
+		return string(ns), e
+	} else {
+		return string(ns), nil
+	}
+}
+
+// UpdateDeployment
+func (c *client) UpdateDeployment(name string, body interface{}) error {
+	return api.NewRequest(c.opts).
+		Patch().
+		Resource("deployments").
+		Name(name).
+		Body(body).
+		Do().
+		Error()
+}