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server.go
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server.go
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/*
Copyright 2016 The Kubernetes Authors All rights reserved.
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.
*/
package app
import (
"fmt"
"net/http"
"os"
"os/signal"
"syscall"
"github.com/golang/glog"
"github.com/skynetservices/skydns/metrics"
"github.com/skynetservices/skydns/server"
"k8s.io/kubernetes/cmd/kube-dns/app/options"
"k8s.io/kubernetes/pkg/api/unversioned"
clientset "k8s.io/kubernetes/pkg/client/clientset_generated/internalclientset"
"k8s.io/kubernetes/pkg/client/restclient"
kclientcmd "k8s.io/kubernetes/pkg/client/unversioned/clientcmd"
kdns "k8s.io/kubernetes/pkg/dns"
)
type KubeDNSServer struct {
// DNS domain name.
domain string
healthzPort int
dnsPort int
kd *kdns.KubeDNS
}
func NewKubeDNSServerDefault(config *options.KubeDNSConfig) *KubeDNSServer {
ks := KubeDNSServer{
domain: config.ClusterDomain,
}
kubeClient, err := newKubeClient(config)
if err != nil {
glog.Fatalf("Failed to create a kubernetes client: %v", err)
}
ks.healthzPort = config.HealthzPort
ks.dnsPort = config.DNSPort
ks.kd, err = kdns.NewKubeDNS(kubeClient, config.ClusterDomain, config.Federations)
if err != nil {
glog.Fatalf("Failed to start kubeDNS: %v", err)
}
return &ks
}
// TODO: evaluate using pkg/client/clientcmd
func newKubeClient(dnsConfig *options.KubeDNSConfig) (clientset.Interface, error) {
var (
config *restclient.Config
err error
)
if dnsConfig.KubeMasterURL != "" && dnsConfig.KubeConfigFile == "" {
// Only --kube-master-url was provided.
config = &restclient.Config{
Host: dnsConfig.KubeMasterURL,
ContentConfig: restclient.ContentConfig{GroupVersion: &unversioned.GroupVersion{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 = dnsConfig.KubeMasterURL // might be "", but that is OK
rules := &kclientcmd.ClientConfigLoadingRules{ExplicitPath: dnsConfig.KubeConfigFile} // 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 %v", config.GroupVersion)
return clientset.NewForConfig(config)
}
func (server *KubeDNSServer) Run() {
setupSignalHandlers()
server.startSkyDNSServer()
server.kd.Start()
server.setupHealthzHandlers()
glog.Infof("Setting up Healthz Handler(/readiness, /cache) on port :%d", server.healthzPort)
glog.Fatal(http.ListenAndServe(fmt.Sprintf(":%d", server.healthzPort), nil))
}
// setupHealthzHandlers sets up a readiness and liveness endpoint for kube2sky.
func (server *KubeDNSServer) setupHealthzHandlers() {
http.HandleFunc("/readiness", func(w http.ResponseWriter, req *http.Request) {
fmt.Fprintf(w, "ok\n")
})
http.HandleFunc("/cache", func(w http.ResponseWriter, req *http.Request) {
serializedJSON, err := server.kd.GetCacheAsJSON()
if err == nil {
fmt.Fprint(w, serializedJSON)
} else {
w.WriteHeader(http.StatusInternalServerError)
fmt.Fprint(w, err)
}
})
}
// setupSignalHandlers runs a goroutine that waits on SIGINT or SIGTERM and logs it
// before exiting.
func setupSignalHandlers() {
sigChan := make(chan os.Signal)
signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM)
go func() {
glog.Fatalf("Received signal: %s", <-sigChan)
}()
}
func (d *KubeDNSServer) startSkyDNSServer() {
glog.Infof("Starting SkyDNS server. Listening on port:%d", d.dnsPort)
skydnsConfig := &server.Config{Domain: d.domain, DnsAddr: fmt.Sprintf("0.0.0.0:%d", d.dnsPort)}
server.SetDefaults(skydnsConfig)
s := server.New(d.kd, skydnsConfig)
if err := metrics.Metrics(); err != nil {
glog.Fatalf("skydns: %s", err)
} else {
glog.Infof("skydns: metrics enabled on :%s%s", metrics.Port, metrics.Path)
}
go s.Run()
}