implement k8s service discovery (#988)

* implement k8s service discovery

* simplify code

* use default namespace if not provided

* disable codecov bot comment

* ignore adhoc dir

* simplify building target in NewClient

* reformat code

* Fix filepath (#990)

* format code, and reorg imports (#991)

* add more unit test

Co-authored-by: anqiansong <anqiansong@gmail.com>

zrpc/internal/resolver/kube/eventhandler.go

@@ -0,0 +1,133 @@
+package kube
+
+import (
+	"sync"
+
+	"github.com/tal-tech/go-zero/core/lang"
+	"github.com/tal-tech/go-zero/core/logx"
+	v1 "k8s.io/api/core/v1"
+)
+
+type EventHandler struct {
+	update    func([]string)
+	endpoints map[string]lang.PlaceholderType
+	lock      sync.Mutex
+}
+
+func NewEventHandler(update func([]string)) *EventHandler {
+	return &EventHandler{
+		update:    update,
+		endpoints: make(map[string]lang.PlaceholderType),
+	}
+}
+
+func (h *EventHandler) OnAdd(obj interface{}) {
+	endpoints, ok := obj.(*v1.Endpoints)
+	if !ok {
+		logx.Errorf("%v is not an object with type *v1.Endpoints", obj)
+		return
+	}
+
+	h.lock.Lock()
+	defer h.lock.Unlock()
+
+	var changed bool
+	for _, sub := range endpoints.Subsets {
+		for _, point := range sub.Addresses {
+			if _, ok := h.endpoints[point.IP]; !ok {
+				h.endpoints[point.IP] = lang.Placeholder
+				changed = true
+			}
+		}
+	}
+
+	if changed {
+		h.notify()
+	}
+}
+
+func (h *EventHandler) OnDelete(obj interface{}) {
+	endpoints, ok := obj.(*v1.Endpoints)
+	if !ok {
+		logx.Errorf("%v is not an object with type *v1.Endpoints", obj)
+		return
+	}
+
+	h.lock.Lock()
+	defer h.lock.Unlock()
+
+	var changed bool
+	for _, sub := range endpoints.Subsets {
+		for _, point := range sub.Addresses {
+			if _, ok := h.endpoints[point.IP]; ok {
+				delete(h.endpoints, point.IP)
+				changed = true
+			}
+		}
+	}
+
+	if changed {
+		h.notify()
+	}
+}
+
+func (h *EventHandler) OnUpdate(oldObj, newObj interface{}) {
+	oldEndpoints, ok := oldObj.(*v1.Endpoints)
+	if !ok {
+		logx.Errorf("%v is not an object with type *v1.Endpoints", oldObj)
+		return
+	}
+
+	newEndpoints, ok := newObj.(*v1.Endpoints)
+	if !ok {
+		logx.Errorf("%v is not an object with type *v1.Endpoints", newObj)
+		return
+	}
+
+	if oldEndpoints.ResourceVersion == newEndpoints.ResourceVersion {
+		return
+	}
+
+	h.Update(newEndpoints)
+}
+
+func (h *EventHandler) Update(endpoints *v1.Endpoints) {
+	h.lock.Lock()
+	defer h.lock.Unlock()
+
+	old := h.endpoints
+	h.endpoints = make(map[string]lang.PlaceholderType)
+	for _, sub := range endpoints.Subsets {
+		for _, point := range sub.Addresses {
+			h.endpoints[point.IP] = lang.Placeholder
+		}
+	}
+
+	if diff(old, h.endpoints) {
+		h.notify()
+	}
+}
+
+func (h *EventHandler) notify() {
+	var targets []string
+
+	for k := range h.endpoints {
+		targets = append(targets, k)
+	}
+
+	h.update(targets)
+}
+
+func diff(o, n map[string]lang.PlaceholderType) bool {
+	if len(o) != len(n) {
+		return true
+	}
+
+	for k := range o {
+		if _, ok := n[k]; !ok {
+			return true
+		}
+	}
+
+	return false
+}