/
kube2dnsimple.go
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/
kube2dnsimple.go
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// kube2dnsimple is a component to automatically update DNSimple according
// to services that are running.
package main
import (
"bytes"
"flag"
"fmt"
"net/url"
"os"
"sync"
"text/template"
"time"
"github.com/golang/glog"
"github.com/vektra/kube2dnsimple/dnsimple"
kapi "k8s.io/kubernetes/pkg/api"
kclient "k8s.io/kubernetes/pkg/client/unversioned"
kcache "k8s.io/kubernetes/pkg/client/unversioned/cache"
kclientcmd "k8s.io/kubernetes/pkg/client/unversioned/clientcmd"
kframework "k8s.io/kubernetes/pkg/controller/framework"
kSelector "k8s.io/kubernetes/pkg/fields"
"k8s.io/kubernetes/pkg/util"
)
var (
// TODO: switch to pflag and make - and _ equivalent.
argDomain = flag.String("domain", "cluster.local", "domain under which to create names")
argMutationTimeout = flag.Duration("timeout", 10*time.Second, "crash after retrying for a specified duration")
argEmail = flag.String("email", "", "email to authenticate with")
argToken = flag.String("token", "", "auth token")
argTemplate = flag.String("template", "", "template to use to create name")
argKubecfgFile = flag.String("kubecfg_file", "", "Location of kubecfg file for access to kubernetes master service; --kube_master_url overrides the URL part of this; if neither this nor --kube_master_url are provided, defaults to service account tokens")
argKubeMasterURL = flag.String("kube_master_url", "", "URL to reach kubernetes master. Env variables in this flag will be expanded.")
)
const (
// Resync period for the kube controller loop.
resyncPeriod = 30 * time.Minute
defaultTemplate = "{{.Service.Name}}.svc.{{.Service.Namespace}}"
)
type kube2dnsimple struct {
ds *dnsimple.Client
tmpl *template.Template
// DNS domain name.
domain string
// mutation timeout.
mutationTimeout time.Duration
// A cache that contains all the endpoints in the system.
endpointsStore kcache.Store
// A cache that contains all the servicess in the system.
servicesStore kcache.Store
// Lock for controlling access to headless services.
mlock sync.Mutex
}
func (ks *kube2dnsimple) removeDNS(service *kapi.Service) error {
name, err := ks.recordName(service)
if err != nil {
return err
}
records, _, err := ks.ds.Domains.ListRecords(ks.domain, name, "CNAME")
if err != nil {
return err
}
for _, rec := range records {
_, err = ks.ds.Domains.DeleteRecord(ks.domain, rec.Id)
if err != nil {
return err
}
}
return nil
}
func (ks *kube2dnsimple) generateRecordsForPortalService(service *kapi.Service) error {
name, err := ks.recordName(service)
if err != nil {
return err
}
records, _, err := ks.ds.Domains.ListRecords(ks.domain, name, "CNAME")
if err != nil {
return err
}
glog.V(2).Infof("%d existing records for %s", len(records), name)
for _, rec := range records {
glog.V(5).Infof("=> '%s' '%s' '%s'", rec.Name, rec.Type, rec.Content)
}
lbs := service.Status.LoadBalancer.Ingress
if len(records) > 0 {
var (
toAdd []kapi.LoadBalancerIngress
toRemove []dnsimple.Record
)
for _, lb := range lbs {
var found bool
for _, rec := range records {
if rec.Type == "CNAME" && rec.Content == lb.Hostname {
found = true
break
}
}
if !found {
toAdd = append(toAdd, lb)
}
}
for _, rec := range records {
var found bool
for _, lb := range lbs {
if rec.Type == "CNAME" && rec.Content == lb.Hostname {
found = true
break
}
}
if !found {
toRemove = append(toRemove, rec)
}
}
for _, rec := range toRemove {
glog.V(2).Infof("Removing unneeded record: %s => %s", rec.Name, rec.Content)
_, err = ks.ds.Domains.DeleteRecord(ks.domain, rec.Id)
if err != nil {
return err
}
}
lbs = toAdd
}
if len(lbs) == 0 {
glog.V(2).Infof("Record '%s' name had no lb updates", name)
return nil
}
for _, lb := range lbs {
var record dnsimple.Record
record.Name = name
record.Type = "CNAME"
record.Content = lb.Hostname
glog.V(2).Infof("Creating CNAME %s.%s => %s", name, ks.domain, lb.Hostname)
_, _, err = ks.ds.Domains.CreateRecord(ks.domain, record)
return err
}
return nil
}
func (ks *kube2dnsimple) addDNS(service *kapi.Service) error {
if len(service.Spec.Ports) == 0 {
glog.Fatalf("unexpected service with no ports: %v", service)
}
if !kapi.IsServiceIPSet(service) {
return nil
}
return ks.generateRecordsForPortalService(service)
}
// Implements retry logic for arbitrary mutator. Crashes after retrying for
// mutation_timeout.
func (ks *kube2dnsimple) mutateOrDie(mutator func() error) {
timeout := time.After(ks.mutationTimeout)
for {
select {
case <-timeout:
glog.Fatalf("Failed to mutate for %v using mutator: %v", ks.mutationTimeout, mutator)
default:
if err := mutator(); err != nil {
delay := 1 * time.Second
glog.V(1).Infof("Failed to mutate using mutator: %v due to: %v. Will retry in: %v", mutator, err, delay)
time.Sleep(delay)
} else {
return
}
}
}
}
// Returns a cache.ListWatch that gets all changes to services.
func createServiceLW(kubeClient *kclient.Client) *kcache.ListWatch {
return kcache.NewListWatchFromClient(kubeClient, "services", kapi.NamespaceAll, kSelector.Everything())
}
// Type to provide additional functionality in the templates
type templateTarget struct {
Service *kapi.Service
}
func (t *templateTarget) Label(name string) interface{} {
return t.Service.Labels[name]
}
func (ks *kube2dnsimple) recordName(s *kapi.Service) (string, error) {
var buf bytes.Buffer
var tt templateTarget
tt.Service = s
err := ks.tmpl.Execute(&buf, &tt)
if err != nil {
return "", err
}
return buf.String(), nil
}
func (ks *kube2dnsimple) newService(obj interface{}) {
if s, ok := obj.(*kapi.Service); ok {
ks.mutateOrDie(func() error { return ks.addDNS(s) })
}
}
func (ks *kube2dnsimple) removeService(obj interface{}) {
if s, ok := obj.(*kapi.Service); ok {
ks.mutateOrDie(func() error { return ks.removeDNS(s) })
}
}
func (ks *kube2dnsimple) updateService(oldObj, newObj interface{}) {
// TODO: Avoid unwanted updates.
ks.removeService(oldObj)
ks.newService(newObj)
}
func expandKubeMasterURL() (string, error) {
parsedURL, err := url.Parse(os.ExpandEnv(*argKubeMasterURL))
if err != nil {
return "", fmt.Errorf("failed to parse --kube_master_url %s - %v", *argKubeMasterURL, err)
}
if parsedURL.Scheme == "" || parsedURL.Host == "" || parsedURL.Host == ":" {
return "", fmt.Errorf("invalid --kube_master_url specified %s", *argKubeMasterURL)
}
return parsedURL.String(), nil
}
// TODO: evaluate using pkg/client/clientcmd
func newKubeClient() (*kclient.Client, error) {
var (
config *kclient.Config
err error
masterURL string
)
// If the user specified --kube_master_url, expand env vars and verify it.
if *argKubeMasterURL != "" {
masterURL, err = expandKubeMasterURL()
if err != nil {
return nil, err
}
}
if masterURL != "" && *argKubecfgFile == "" {
// Only --kube_master_url was provided.
config = &kclient.Config{
Host: masterURL,
Version: "v1",
}
} else {
// We either have:
// 1) --kube_master_url and --kubecfg_file
// 2) just --kubecfg_file
// 3) neither flag
// In any case, the logic is the same. If (3), this will automatically
// fall back on the service account token.
overrides := &kclientcmd.ConfigOverrides{}
overrides.ClusterInfo.Server = masterURL // might be "", but that is OK
rules := &kclientcmd.ClientConfigLoadingRules{ExplicitPath: *argKubecfgFile} // might be "", but that is OK
if config, err = kclientcmd.NewNonInteractiveDeferredLoadingClientConfig(rules, overrides).ClientConfig(); err != nil {
return nil, err
}
}
glog.Infof("Using %s for kubernetes master", config.Host)
glog.Infof("Using kubernetes API %s", config.Version)
return kclient.New(config)
}
func watchForServices(kubeClient *kclient.Client, ks *kube2dnsimple) kcache.Store {
serviceStore, serviceController := kframework.NewInformer(
createServiceLW(kubeClient),
&kapi.Service{},
resyncPeriod,
kframework.ResourceEventHandlerFuncs{
AddFunc: ks.newService,
DeleteFunc: ks.removeService,
UpdateFunc: ks.updateService,
},
)
go serviceController.Run(util.NeverStop)
return serviceStore
}
func main() {
flag.Parse()
domain := *argDomain
ds := dnsimple.NewClient(*argToken, *argEmail)
templateText := *argTemplate
if templateText == "" {
templateText = defaultTemplate
}
tmpl, err := template.New("record").Parse(templateText)
if err != nil {
glog.Fatalf("Unable to parse template: %s", err)
}
ks := kube2dnsimple{
ds: ds,
domain: domain,
mutationTimeout: *argMutationTimeout,
tmpl: tmpl,
}
kubeClient, err := newKubeClient()
if err != nil {
glog.Fatalf("Failed to create a kubernetes client: %v", err)
}
ks.servicesStore = watchForServices(kubeClient, &ks)
select {}
}