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observer.go
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observer.go
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// Package observer polls the Kubernetes api-server to discover all supported
// API groups/object kinds, and launch a new controller for each of them.
// Due to CRD/TPR, new API groups / object kinds may appear at any time,
// that's why we keep polling the API server.
package observer
import (
"fmt"
"strings"
"sync"
"time"
"github.com/bpineau/katafygio/pkg/controller"
"github.com/bpineau/katafygio/pkg/event"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/apimachinery/pkg/runtime/schema"
"k8s.io/client-go/discovery"
"k8s.io/client-go/dynamic"
"k8s.io/client-go/rest"
"k8s.io/client-go/tools/cache"
)
const discoveryInterval = 60 * time.Second
// ControllerFactory make controllers generation interchangeable
type ControllerFactory interface {
NewController(client cache.ListerWatcher, notifier event.Notifier, name string) controller.Interface
}
type controllerCollection map[string]controller.Interface
type restclient interface {
GetRestConfig() *rest.Config
}
type logger interface {
Infof(format string, args ...interface{})
Errorf(format string, args ...interface{})
}
// Observer watch api-server and manage kubernetes controllers lifecyles
type Observer struct {
sync.RWMutex // protect ctrls
stopCh chan struct{}
doneCh chan struct{}
notifier event.Notifier
discovery discovery.DiscoveryInterface
cpool dynamic.ClientPool
ctrls controllerCollection
factory ControllerFactory
logger logger
excludedkind []string
}
type gvk struct {
groupVersion schema.GroupVersion
apiResource metav1.APIResource
}
type resources map[string]*gvk
// New returns a new observer, that will watch API resources and create controllers
func New(log logger, client restclient, notif event.Notifier, factory ControllerFactory, excluded []string) *Observer {
return &Observer{
notifier: notif,
discovery: discovery.NewDiscoveryClientForConfigOrDie(client.GetRestConfig()),
cpool: dynamic.NewDynamicClientPool(client.GetRestConfig()),
ctrls: make(controllerCollection),
factory: factory,
logger: log,
excludedkind: excluded,
}
}
// Start starts the observer in a detached goroutine
func (c *Observer) Start() *Observer {
c.logger.Infof("Starting all kubernetes controllers")
c.stopCh = make(chan struct{})
c.doneCh = make(chan struct{})
go func() {
ticker := time.NewTicker(discoveryInterval)
defer ticker.Stop()
defer close(c.doneCh)
for {
err := c.refresh()
if err != nil {
c.logger.Errorf("Refresh failed: %v", err)
}
select {
case <-c.stopCh:
return
case <-ticker.C:
}
}
}()
return c
}
// Stop halts the observer
func (c *Observer) Stop() {
c.logger.Infof("Stopping all kubernetes controllers")
c.stopCh <- struct{}{}
c.RLock()
for _, ct := range c.ctrls {
ct.Stop()
}
c.RUnlock()
<-c.doneCh
}
func (c *Observer) refresh() error {
c.Lock()
defer c.Unlock()
groups, err := c.discovery.ServerResources()
if err != nil {
return fmt.Errorf("failed to collect server resources: %v", err)
}
for name, res := range c.expandAndFilterAPIResources(groups) {
if _, ok := c.ctrls[name]; ok {
continue
}
kind := res.apiResource.Kind
gk := res.groupVersion.WithKind(kind)
cname := strings.ToLower(kind)
cl, err := c.cpool.ClientForGroupVersionKind(gk)
if err != nil {
return fmt.Errorf("failed to get a client for %s", name)
}
client := cl.Resource(res.apiResource.DeepCopy(), metav1.NamespaceAll)
c.ctrls[name] = c.factory.NewController(client, c.notifier, cname)
go c.ctrls[name].Start()
}
return nil
}
// The api-server may expose a resource under several API groups, for backward
// compatibility. We'll want to ignore lower priorities "cohabitations":
// cf. kubernetes/cmd/kube-apiserver/app/server.go
var preferredVersions = map[string]string{
"apps:deployment": "extensions:deployment",
"apps:daemonset": "extensions:daemonset",
"apps:replicaset": "extensions:replicaset",
"events:events": ":events",
"extensions:podsecuritypolicies": "policy:podsecuritypolicies",
"networking.k8s.io:networkpolicies": "extensions:networkpolicies",
}
func (c *Observer) expandAndFilterAPIResources(groups []*metav1.APIResourceList) resources {
resources := make(map[string]*gvk)
for _, group := range groups {
gv, err := schema.ParseGroupVersion(group.GroupVersion)
if err != nil {
c.logger.Errorf("unparsable group version: %v", err)
continue
}
for _, ar := range group.APIResources {
// remove subresources (like job/status)
if strings.ContainsRune(ar.Name, '/') {
continue
}
// remove user filtered objet kinds
if isExcluded(c.excludedkind, ar.Kind) {
continue
}
// only consider resources that are getable, listable an watchable
if !isSubList(ar.Verbs, []string{"list", "get", "watch"}) {
continue
}
resources[strings.ToLower(gv.Group+":"+ar.Kind)] = &gvk{
groupVersion: gv,
apiResource: ar,
}
}
}
for preferred, obsolete := range preferredVersions {
if _, ok := resources[preferred]; ok {
delete(resources, obsolete)
}
}
return resources
}
func isExcluded(excluded []string, name string) bool {
lname := strings.ToLower(name)
for _, ctl := range excluded {
if strings.Compare(lname, strings.ToLower(ctl)) == 0 {
return true
}
}
return false
}
func isSubList(containing []string, contained []string) bool {
containing:
for _, in := range contained {
for _, out := range containing {
if strings.Compare(in, out) == 0 {
continue containing
}
}
return false
}
return true
}