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Controller란
- Pod의 개수를 보장
Controller 종류
ReplicationController
- 요구하는 Pod의 개수를 보장하며 파드 집합의 실행을 항상 안정적으로 유지하는 것을 목표
. 요구하는 Pod의 개수가 부족하면 template를 이용해 Pod를 추가
. 요구하는 Pod 수 보다 많으면 최근에 생성된 Pod를 삭제
- 기본구성
. selector
. replicas
. template
apiVersoin: v1
kind: ReplicationController
metadata:
name: <RC_이름>
spec:
replicas: <배포갯수>
selector:
key: value
template:
<컨테이너 템플릿>※ Pod 템플릿은 selector의 키: value label을 포함해야 한다.
apiVersion: v1
kind: ReplicationController
metadata:
name: rc-nginx
spec:
replicas: 3
selector:
app: webui
template:
metadata:
name: nginx-pod
labels:
app: webui
spec:
containers:
- name: nginx-container
image: nginx:1.14
rc-nginx.yaml를 통해 ReplicationController pod 실행
# kubectl create -f rc-nginx.yaml
replicationcontroller/rc-nginx created
kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
rc-nginx-s4gmk 1/1 Running 0 95s 10.36.0.1 node1.example.com <none> <none>
rc-nginx-xpqtw 1/1 Running 0 95s 10.36.0.2 node1.example.com <none> <none>
rc-nginx-zgsst 1/1 Running 0 95s 10.44.0.1 node2.example.com <none> <none>
kubectl get replicationcontrollers
NAME DESIRED CURRENT READY AGE
rc-nginx 3 3 3 2m2s
kubectl get rc
NAME DESIRED CURRENT READY AGE
rc-nginx 3 3 3 2m26s
selector: app=webui 를 가진 3개의 pod 생성
kubectl describe rc rc-nginx
Name: rc-nginx
Namespace: default
Selector: app=webui
Labels: app=webui
Annotations: <none>
Replicas: 3 current / 3 desired
Pods Status: 3 Running / 0 Waiting / 0 Succeeded / 0 Failed
Pod Template:
Labels: app=webui
Containers:
nginx-container:
Image: nginx:1.14
Port: <none>
Host Port: <none>
Environment: <none>
Mounts: <none>
Volumes: <none>
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal SuccessfulCreate 2m40s replication-controller Created pod: rc-nginx-zgsst
Normal SuccessfulCreate 2m40s replication-controller Created pod: rc-nginx-xpqtw
Normal SuccessfulCreate 2m40s replication-controller Created pod: rc-nginx-s4gmk
3개의 pod를 구성중인 상태에서 app=webui 로 설정된 redis.yaml을 구성하여 실행
kubectl run redis --image=redis --dry-run
W1205 22:18:21.207618 5358 helpers.go:663] --dry-run is deprecated and can be replaced with --dry-run=client.
pod/redis created (dry run)
kubectl run redis --image=redis --labels=app=webui --dry-run
W1205 22:18:59.078405 5548 helpers.go:663] --dry-run is deprecated and can be replaced with --dry-run=client.
pod/redis created (dry run)
kubectl run redis --image=redis --labels=app=webui --dry-run -o yaml > redis.yaml
W1205 22:19:29.933593 5674 helpers.go:663] --dry-run is deprecated and can be replaced with --dry-run=client.
아래와 같이 yaml 파일 수정
redis.yaml
apiVersion: v1
kind: Pod
metadata:
labels:
app: webui
name: redis
spec:
containers:
- image: redis
name: redis
redis.yaml 실행 후 pod 정보를 보면 replicas 가 3개로 설정이 되었기 때문에 pod가 생성되지 않음
kubectl get pod --show-labels
NAME READY STATUS RESTARTS AGE LABELS
rc-nginx-s4gmk 1/1 Running 0 6m6s app=webui
rc-nginx-xpqtw 1/1 Running 0 6m6s app=webui
rc-nginx-zgsst 1/1 Running 0 6m6s app=webui
kubectl create -f redis.yaml
pod/redis created
kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
rc-nginx-s4gmk 1/1 Running 0 7m13s 10.36.0.1 node1.example.com <none> <none>
rc-nginx-xpqtw 1/1 Running 0 7m13s 10.36.0.2 node1.example.com <none> <none>
rc-nginx-zgsst 1/1 Running 0 7m13s 10.44.0.1 node2.example.com <none> <none>
redis 0/1 Terminating 0 3s <none> node2.example.com <none> <none>
edit 에서 replicas 를 3 → 4개로 수정
kubectl edit rc rc-nginx
Please edit the object below. Lines beginning with a '#' will be ignored,
# and an empty file will abort the edit. If an error occurs while saving this file will be
# reopened with the relevant failures.
#
apiVersion: v1
kind: ReplicationController
metadata:
creationTimestamp: "2022-12-05T13:14:21Z"
generation: 3
labels:
app: webui
name: rc-nginx
namespace: default
resourceVersion: "62250"
uid: 3797522a-2dad-4227-bc84-1ca622937b57
spec:
replicas: 4
selector:
app: webui
template:
metadata:
creationTimestamp: null
labels:
app: webui
name: nginx-pod
spec:
containers:
- image: nginx:1.14
imagePullPolicy: IfNotPresent
name: nginx-container
resources: {}
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
dnsPolicy: ClusterFirst
restartPolicy: Always
schedulerName: default-scheduler
securityContext: {}
terminationGracePeriodSeconds: 30
status:
availableReplicas: 2
fullyLabeledReplicas: 2
4개의 pod 가 실행중인것을 확인
kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
rc-nginx-h884d 1/1 Running 0 10s 10.44.0.2 node2.example.com <none> <none>
rc-nginx-s4gmk 1/1 Running 0 8m16s 10.36.0.1 node1.example.com <none> <none>
rc-nginx-xpqtw 1/1 Running 0 8m16s 10.36.0.2 node1.example.com <none> <none>
rc-nginx-zgsst 1/1 Running 0 8m16s 10.44.0.1 node2.example.com <none> <none>
scale을 통해 replicas 개수를 변경시 가장 최근의 pod가 삭제된것을 확인 가능
kubectl scale rc rc-nginx --replicas=2
replicationcontroller/rc-nginx scaled
kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
rc-nginx-s4gmk 1/1 Running 0 9m 10.36.0.1 node1.example.com <none> <none>
rc-nginx-xpqtw 1/1 Running 0 9m 10.36.0.2 node1.example.com <none> <none>
위와 같은 구성에서 edit을 통해 nginx 버전을 1.15 버전으로 변경시 pod에 변화는 없다
kubectl edit rc rc-nginx
apiVersion: v1
kind: ReplicationController
metadata:
creationTimestamp: "2022-12-05T13:14:21Z"
generation: 4
labels:
app: webui
name: rc-nginx
namespace: default
resourceVersion: "62924"
uid: 3797522a-2dad-4227-bc84-1ca622937b57
spec:
replicas: 2
selector:
app: webui
template:
metadata:
creationTimestamp: null
labels:
app: webui
name: nginx-pod
spec:
containers:
- image: nginx:1.15
imagePullPolicy: IfNotPresent
name: nginx-container
resources: {}
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
dnsPolicy: ClusterFirst
restartPolicy: Always
schedulerName: default-scheduler
securityContext: {}
terminationGracePeriodSeconds: 30
pod delete 후 nginx 버전을 확인하면 nginx 버전이 변경된 것을 확인할 수 있다.
kubectl delete pod rc-nginx-s4gmk
pod "rc-nginx-s4gmk" deleted
kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
rc-nginx-jq8rw 1/1 Running 0 5m28s 10.44.0.1 node2.example.com <none> <none>
rc-nginx-xpqtw 1/1 Running 0 21m 10.36.0.2 node1.example.com <none> <none>
kubectl describe pod rc-nginx-jq8rw
Containers:
nginx-container:
Container ID: containerd://b1e328cd8200c021cb346689a4db68e82caf8359596798702930390b73e76f74
Image: nginx:1.15
Image ID: docker.io/library/nginx@sha256:23b4dcdf0d34d4a129755fc6f52e1c6e23bb34ea011b315d87e193033bcd1b68
[참고]
- https://www.youtube.com/watch?v=5X3t6VJH2vQ&list=PLApuRlvrZKohaBHvXAOhUD-RxD0uQ3z0c&index=17
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