This document provides an overview of Kubernetes and its components. It discusses the Go programming language features used in Kubernetes. It also describes how Kubernetes is architected, including the kube-apiserver, kube-scheduler, Kubelet, reconciliation process, and networking with Flannel. The presenter is Anseungkyu who worked on OpenStack private clouds and is now the deputy representative for OpenStack Korea.

1. A deep dive into Kubernetes
오픈스택코리아 안승규
2016년 2월 18일

2. 발표자는 누구?
• OpenStack 기반 Private Cloud 구축 (2011년 7월 ~ 2015년 2월)
at 삼성SDS
• 오픈스택 코리아 부대표
• 안승규.com
http://www.ahnseungkyu.com
• e-mail
seungkyua@gmail.com

3. Go language
• shorthand
a := 42
b := “Hello”
• interface and receiver
type Kubelet struct { … }
func (kl *Kubelet) syncLoop(..) { … }
type SyncHandler interface {
HandlePodSyncs(pods []*api.Pod)
}
func (kl *Kubelet) HandlePodSyncs(pods []*api.Pod)
• comma ok idiom
value, ok := map[key]
key, value := range map

4. Go language (계속)
• make : slice, map, channel
c := make(chan int)
• go rou>ne
go func() {
for i := 0; i<10; i++ {
c <- I
}
}()
go func() {
for {
fmt.Println(<-c)
}
}()

5. 환경 구성
[ 서버 구성 ]
Master : 192.168.75.211 (etcd, kube-apiserver, kube-controller-manager, kube-scheduler)
Node01 : 192.168.75.212 (kube-proxy, kubelet)
Node02 : 192.168.75.213 (kube-proxy, kubelet)
버전 : etcd-2.2.1, flannel-0.5.5, k8s-1.1.2
[ 환경 변수 ]
export GOROOT=/usr/local/go
export PATH=$PATH:/usr/local/go/bin
export GOPATH=$HOME/Documents/go_workspace:$HOME/Documents/go_workspace/src/k8s.io
/kubernetes/Godeps/_workspace
export PATH=$HOME/Documents/go_workspace/bin:$PATH
[ 소스 다운로드 ]
$ go get k8s.io/kubernetes
$ cd ~/Documents/go_workspace/src/k8s.io/kubernetes

6. WebStorm 세팅
Go Libraries : ...go_workspace/src/k8s.io/kubernetes/Godeps/_workspace

7. Component
[ Pod ]
Container group
Same network namespace, ip (Apache -> (localhost, port) -> Tomcat)
Shared volumes
[ Replication controllers ]
Managing pod numbers
[ Services ]
Route to pod (using labels)
IP per service
type : Load balancer (GCE), NodePort (iptables)

8. Kubernetes Architecture
kube-apiserver
kube-controller-manager
kubelet
kube-scheduler
etcd
kube-proxy
Master Node

9. Reconcilia>on
[ Controller-manager ]
EndpointController
ReplicationManager
NodeController
ServiceController
ResourceQuotaController
NamespaceController
PersistentVolumeClaimBinder
PersistentVolumeRecycler
[ Kubelet ]
klet.syncNodeStatus
klet.syncPod

10. kube-apiserver
cmd/kube-apiserver/apiserver.go
cmd/kube-apiserver/app/server.go : Run()
pkg/master/master.go : init()
podStorage, eventStorage, namespaceStorage,
nodeStorage, serviceStorage, controllerStorage,
namespaceRegistry, serviceNodePortRegistry,
endpointRegistry, nodeRegistry, serviceRegistry
pkg/registry/service/registry.go
type Registry interface {
ListServices()
CreateService()
GetService()
DeleteService()
UpdateService()
}

11. kube-apiserver
pkg/master/master.go : init()
m.storage = map[string]rest.Storage{
"pods": podStorage.Pod,
"pods/attach": podStorage.Attach,
"pods/status": podStorage.Status,
"pods/log": podStorage.Log,
"pods/exec": podStorage.Exec,
"replicationControllers": controllerStorage,
"replicationControllers/status": controllerStatusStorage,
"services": service.NewStorage(),
"endpoints": endpointsStorage,
"nodes": nodeStorage,
"nodes/status": nodeStatusStorage,
}
pkg/apiserver/apiserver.go : InstallREST()
ws *restful.WebService
container *restful.Container
container.Add(ws)

12. kube-scheduler
plugin/cmd/kube-scheduler/scheduler.go
plugin/pkg/scheduler/scheduler.go
type Config struct {
Modeler SystemModeler
NodeLister algorithm.NodeLister
Algorithm algorithm.ScheduleAlgorithm
Binder Binder
NextPod func() *api.Pod
}
plugin/pkg/scheduler/factory/factory.go : CreateFromConfig()
scheduler.NewGenericScheduler(predicateFuncs, priorityConfigs, f.PodLister, r)
plugin/pkg/scheduler/generic_scheduler.go : Schedule()
nodeLister.List()
findNodesThatFit()
PrioritizeNodes()
sort.Sort(sort.Reverse(priorityList))
hosts := getBestHosts(priorityList)
ix := g.random.Int() % len(hosts)

13. Kubelet Diagram
server.go
startKubelet
cmd/kubelet pkg/kubelet
server.go
RunKubelet
server.go
Run
kubelet.go
registerWithApiserver
updateNodeStatus
kubelet.go
syncNodeStatus
kubelet.go
NewMainKubelet
server.go
createAndInitKubelet
kubelet.go
ListenAndServe
server.go
ListenAndServeKubeletServer
server.go
InstallDefaultHandlers
kubelet.go
Run
kubelet.go
syncLoop
pkg/kubelet /
cadvisor
cadvisor_linux.go
New
kubelet.go
HandlePodCleanups
kubelet.go
cleanupOrphanedVolumes
kubelet.go
syncLoopIteration
kubelet.go
HandlePodAdditions
kubelet.go
HandlePodUpdates
kubelet.go
HandlePodDeletions
kubelet.go
HandlePodSyncs

14. Network (Flannel)
eth0
192.168.75.213
flanneld
docker0
172.16.23.1/24
flannel0
172.16.23.0/16
tomcat8-cl
cec
node02
kube-dns-v
9-59m06
veth905783f vethc248789
172.16.23.2 172.16.23.3

15. Network (Flannel)
eth0
192.168.75.213
flanneld
docker0
172.16.23.1/24
flannel0
172.16.23.0/16
tomcat8-cl
cec
node02
kube-dns-v
9-59m06
veth905783f vethc248789
172.16.23.2 172.16.23.3

16. 마치며…
• Cloud Foundry? OpenShiY? Kubernetes?
• 오픈스택 코리아 홈페이지
http://openstack.or.kr
홈페이지 개편 중