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update docker's resolv.conf file with options ndots:5

pull/6/head
Abhishek Shah 2015-06-23 16:36:06 -07:00
parent d1301d2b2a
commit 23caf446ae
4 changed files with 110 additions and 62 deletions
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6
contrib/for-tests/jessie-dnsutils/Dockerfile Normal file
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@ -0,0 +1,6 @@
FROM debian:jessie
MAINTAINER Abhishek Shah "abshah@google.com"
RUN apt-get -q update && \
apt-get install -y dnsutils && \
apt-get clean

8
contrib/for-tests/jessie-dnsutils/Makefile Normal file
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@ -0,0 +1,8 @@
all:
@echo "try 'make image' or 'make push'"
image:
docker build -t gcr.io/google_containers/jessie-dnsutils .
push:
gcloud docker push gcr.io/google_containers/jessie-dnsutils

41
pkg/kubelet/dockertools/manager.go
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@ -60,6 +60,10 @@ const (
kubernetesPodLabel = "io.kubernetes.pod.data"
kubernetesContainerLabel = "io.kubernetes.container.name"
// ndots specifies the minimum number of dots that a domain name must contain for the resolver to consider it as FQDN (fully-qualified)
// we want to able to consider SRV lookup names like _dns._udp.kube-dns.default.svc to be considered relative.
// hence, setting ndots to be 5.
ndotsDNSOption = "options ndots:5\n"
)
// DockerManager implements the Runtime interface.
@ -1221,6 +1225,13 @@ func (dm *DockerManager) runContainerInPod(pod *api.Pod, container *api.Containe
}
if container.Name == PodInfraContainerName {
util.ApplyOomScoreAdj(containerInfo.State.Pid, podOomScoreAdj)
// currently, Docker does not have a flag by which the ndots option can be passed.
// (A seperate issue has been filed with Docker to add a ndots flag)
// The addNDotsOption call appends the ndots option to the resolv.conf file generated by docker.
// This resolv.conf file is shared by all containers of the same pod, and needs to be modified only once per pod.
// we modify it when the pause container is created since it is the first container created in the pod since it holds
// the networking namespace.
err = addNDotsOption(containerInfo.ResolvConfPath)
} else {
// Children processes of docker daemon will inheritant the OOM score from docker
// daemon process. We explicitly apply OOM score 0 by default to the user
@ -1231,6 +1242,36 @@ func (dm *DockerManager) runContainerInPod(pod *api.Pod, container *api.Containe
return kubeletTypes.DockerID(id), err
}
func addNDotsOption(resolvFilePath string) error {
if len(resolvFilePath) == 0 {
glog.Errorf("DNS ResolvConfPath is empty.")
return nil
}
if _, err := os.Stat(resolvFilePath); os.IsNotExist(err) {
return fmt.Errorf("DNS ResolvConfPath specified but does not exist. It could not be updated: %s", resolvFilePath)
}
glog.V(4).Infof("DNS ResolvConfPath exists: %s. Will attempt to add ndots option: %s", resolvFilePath, ndotsDNSOption)
if err := appendToFile(resolvFilePath, ndotsDNSOption); err != nil {
glog.Errorf("resolv.conf could not be updated. err:%v", err)
return err
}
return nil
}
func appendToFile(filePath, stringToAppend string) error {
f, err := os.OpenFile(filePath, os.O_APPEND|os.O_WRONLY, 0644)
if err != nil {
return err
}
defer f.Close()
_, err = f.WriteString(stringToAppend)
return err
}
// createPodInfraContainer starts the pod infra container for a pod. Returns the docker container ID of the newly created container.
func (dm *DockerManager) createPodInfraContainer(pod *api.Pod) (kubeletTypes.DockerID, error) {
start := time.Now()

117
test/e2e/dns.go
View File

@ -38,7 +38,7 @@ var dnsServiceLableSelector = labels.Set{
"kubernetes.io/cluster-service": "true",
}.AsSelector()
func createDNSPod(namespace, probeCmd string) *api.Pod {
func createDNSPod(namespace, wheezyProbeCmd, jessieProbeCmd string) *api.Pod {
pod := &api.Pod{
TypeMeta: api.TypeMeta{
Kind: "Pod",
@ -78,7 +78,18 @@ func createDNSPod(namespace, probeCmd string) *api.Pod {
{
Name: "querier",
Image: "gcr.io/google_containers/dnsutils",
Command: []string{"sh", "-c", probeCmd},
Command: []string{"sh", "-c", wheezyProbeCmd},
VolumeMounts: []api.VolumeMount{
{
Name: "results",
MountPath: "/results",
},
},
},
{
Name: "jessie-querier",
Image: "gcr.io/google_containers/jessie-dnsutils",
Command: []string{"sh", "-c", jessieProbeCmd},
VolumeMounts: []api.VolumeMount{
{
Name: "results",
@ -92,7 +103,7 @@ func createDNSPod(namespace, probeCmd string) *api.Pod {
return pod
}
func createProbeCommand(namesToResolve []string) (string, []string) {
func createProbeCommand(namesToResolve []string, fileNamePrefix string) (string, []string) {
fileNames := make([]string, 0, len(namesToResolve)*2)
probeCmd := "for i in `seq 1 600`; do "
for _, name := range namesToResolve {
@ -103,10 +114,10 @@ func createProbeCommand(namesToResolve []string) (string, []string) {
if strings.HasPrefix(name, "_") {
lookup = "SRV"
}
fileName := fmt.Sprintf("udp@%s", name)
fileName := fmt.Sprintf("%s_udp@%s", fileNamePrefix, name)
fileNames = append(fileNames, fileName)
probeCmd += fmt.Sprintf(`test -n "$$(dig +notcp +noall +answer +search %s %s)" && echo OK > /results/%s;`, name, lookup, fileName)
fileName = fmt.Sprintf("tcp@%s", name)
fileName = fmt.Sprintf("%s_tcp@%s", fileNamePrefix, name)
fileNames = append(fileNames, fileName)
probeCmd += fmt.Sprintf(`test -n "$$(dig +tcp +noall +answer +search %s %s)" && echo OK > /results/%s;`, name, lookup, fileName)
}
@ -140,6 +151,36 @@ func assertFilesExist(fileNames []string, fileDir string, pod *api.Pod, client *
Expect(len(failed)).To(Equal(0))
}
func validateDNSResults(f *Framework, pod *api.Pod, fileNames []string) {
By("submitting the pod to kubernetes")
podClient := f.Client.Pods(f.Namespace.Name)
defer func() {
By("deleting the pod")
defer GinkgoRecover()
podClient.Delete(pod.Name, nil)
}()
if _, err := podClient.Create(pod); err != nil {
Failf("Failed to create %s pod: %v", pod.Name, err)
}
expectNoError(f.WaitForPodRunning(pod.Name))
By("retrieving the pod")
pod, err := podClient.Get(pod.Name)
if err != nil {
Failf("Failed to get pod %s: %v", pod.Name, err)
}
// Try to find results for each expected name.
By("looking for the results for each expected name from probiers")
assertFilesExist(fileNames, "results", pod, f.Client)
// TODO: probe from the host, too.
Logf("DNS probes using %s succeeded\n", pod.Name)
}
var _ = Describe("DNS", func() {
f := NewFramework("dns")
@ -175,38 +216,13 @@ var _ = Describe("DNS", func() {
namesToResolve = append(namesToResolve, "metadata")
}
probeCmd, fileNames := createProbeCommand(namesToResolve)
wheezyProbeCmd, wheezyFileNames := createProbeCommand(namesToResolve, "wheezy")
jessieProbeCmd, jessieFileNames := createProbeCommand(namesToResolve, "jessie")
// Run a pod which probes DNS and exposes the results by HTTP.
By("creating a pod to probe DNS")
pod := createDNSPod(f.Namespace.Name, probeCmd)
By("submitting the pod to kubernetes")
podClient = f.Client.Pods(f.Namespace.Name)
defer func() {
By("deleting the pod")
defer GinkgoRecover()
podClient.Delete(pod.Name, nil)
}()
if _, err := podClient.Create(pod); err != nil {
Failf("Failed to create %s pod: %v", pod.Name, err)
}
expectNoError(f.WaitForPodRunning(pod.Name))
By("retrieving the pod")
pod, err = podClient.Get(pod.Name)
if err != nil {
Failf("Failed to get pod %s: %v", pod.Name, err)
}
// Try to find results for each expected name.
By("looking for the results for each expected name")
assertFilesExist(fileNames, "results", pod, f.Client)
// TODO: probe from the host, too.
Logf("DNS probes using %s succeeded\n", pod.Name)
pod := createDNSPod(f.Namespace.Name, wheezyProbeCmd, jessieProbeCmd)
validateDNSResults(f, pod, append(wheezyFileNames, jessieFileNames...))
})
It("should provide DNS for services", func() {
if providerIs("vagrant") {
@ -283,38 +299,15 @@ var _ = Describe("DNS", func() {
fmt.Sprintf("_http._tcp.%s.%s.svc", regularService.Name, f.Namespace.Name),
}
probeCmd, fileNames := createProbeCommand(namesToResolve)
wheezyProbeCmd, wheezyFileNames := createProbeCommand(namesToResolve, "wheezy")
jessieProbeCmd, jessieFileNames := createProbeCommand(namesToResolve, "jessie")
// Run a pod which probes DNS and exposes the results by HTTP.
By("creating a pod to probe DNS")
pod := createDNSPod(f.Namespace.Name, probeCmd)
pod := createDNSPod(f.Namespace.Name, wheezyProbeCmd, jessieProbeCmd)
pod.ObjectMeta.Labels = testServiceSelector
By("submitting the pod to kubernetes")
podClient = f.Client.Pods(f.Namespace.Name)
defer func() {
By("deleting the pod")
defer GinkgoRecover()
podClient.Delete(pod.Name, nil)
}()
if _, err := podClient.Create(pod); err != nil {
Failf("Failed to create %s pod: %v", pod.Name, err)
}
expectNoError(f.WaitForPodRunning(pod.Name))
By("retrieving the pod")
pod, err = podClient.Get(pod.Name)
if err != nil {
Failf("Failed to get pod %s: %v", pod.Name, err)
}
// Try to find results for each expected name.
By("looking for the results for each expected name")
assertFilesExist(fileNames, "results", pod, f.Client)
// TODO: probe from the host, too.
Logf("DNS probes using %s succeeded\n", pod.Name)
validateDNSResults(f, pod, append(wheezyFileNames, jessieFileNames...))
})
})