Kubernetes Part4
Class 88th Kubernetes Part4 August 14th
Replication and Deployment
Step1:Create one Ec2 machine, For Install kubectl, install the cluster Kops
go though part3
https://kops.sigs.k8s.io/getting_started/install/
[root@ip-10-0-0-22 ~]# kops version
Client version: 1.33.0 (git-v1.33.0)
Step2: Replication controller, This one of the cluster when every delete the pod ,automatically create one more pod this Kubernetes give feature.
Step3: Create Cluster
[root@ip-10-0-0-22 ~]# kops create cluster --name kopsclstr.k8s.local --zones eu-west-2b,eu-west-2a --master-count 1 --master-size c7i-flex.large --master-volume-size 20 --node-count 2 --node-size t3.micro --node-volume-size=15 --image=ami-044415bb13eee2391
[root@ip-10-0-0-22 ~]# kops update cluster --name kopsclstr.k8s.local --yes --admin
--List of cluster
[root@ip-10-0-0-22 ~]# kops get cluster
NAME CLOUD ZONES
kopsclstr.k8s.local aws eu-west-2a,eu-west-2b
The Draw Back
In the above both methos we can be able create a pod but
what if we delete the pod?
One you delete thw pod we cannot able to access the pod, so
it will create a lot difficulty in real time.
Note: Self healing is not available here.
To Overcome this on we use some kubernetes components called
RC,RS,
Deployment ,Deamon SETS ,etc..
(Pod object, RC replication control, RS Replication sets)
REPLICAS IN KUBERNETES:
·
Before Kubernetes, other tools did not provide
important and customized feature like scaling and replication.
·
When Kubernetes was introduced, replication and
scaling were the premium features that increased the popularity of this
container orchestration tool.
·
Replication means that if the pods desired state
is set to 3 and whatever any pod fails,
this will lead to a reduction in the downtime of the application.
·
Scaling means if the load becomes increases on
the application, then Kubernetes increase the number of pods according to the
load on the application
- ReplicationController is an object in kubernetes that was
introduced in v1 of kubernetes which helps to meet the desired state of the
kubernetes cluster from the current state.Replicationcontroller works on
requality-base controllers only.
- ReplicaSet is an object in Kubernetes and it is an advanced
version of ReplicationController. ReplicaSet works on the Equality-base controllers
and set-base Controllers.
Step3: First We create the RC, RC will create the Pods ,we need inform the RC how many pods are required ,RC maintained the Pods every 5 sec it will check ,if any pod went down replication controller
automatically create the Pod , We can create replicationController Two ways
1.Imperative 2.Declarative (manifest file) we use this real time
[root@ip-10-0-0-22 ~]# export KOPS_STATE_STORE=s3://ccitpublicbucket1
Part1: Replicationcontroller with name myrc
Part2: pod creation, Replicationcontroller specification, count 3 , selector is select the label using template created metadata added the labels, for every pod one label will createPart3: Container
root@ip-10-0-0-22 ~]# vi manifest.yaml
[root@ip-10-0-0-22 ~]# cat manifest.yaml
apiVersion: v1
kind: ReplicationController
metadata:
name: myrc
spec:
replicas: 3 # Fixed: lowercase and proper spacing
selector: # Proper selector definition
app: swiggy
template: # Moved to top-level under spec
metadata:
labels:
app: swiggy # Must match selector
spec:
containers:
- name: container1
image: shaikmustafa/cycle
ports:
- containerPort: 80
Step4: As you observer myrc name of replicate some random name attached
Before
[root@ip-10-0-0-22 ~]# kubectl get pods
No resources found in default namespace.
[root@ip-10-0-0-22 ~]# kubectl create -f manifest.yaml
replicationcontroller/myrc created
[root@ip-10-0-0-22 ~]# cat manifest.yaml
After :
[root@ip-10-0-0-22 ~]# kubectl get pods
NAME READY STATUS RESTARTS AGE
myrc-bvch9 1/1 Running 0 2m54s
myrc-g6w5t 1/1 Running 0 2m54s
myrc-h58kj 1/1 Running 0 2m54s
[root@ip-10-0-0-22 ~]#
[root@ip-10-0-0-22 ~]# kubectl get rc
NAME DESIRED CURRENT READY AGE
myrc 3 3 3 3m41s
Step5: See Deleted one pod myrc-bvch9, automatically 9sec ,created one more pod
[root@ip-10-0-0-22 ~]# kubectl delete pod myrc-bvch9
pod "myrc-bvch9" deleted
[root@ip-10-0-0-22 ~]# kubectl get pods --show-labels
NAME READY STATUS RESTARTS AGE LABELS
myrc-g6w5t 1/1 Running 0 7m53s app=swiggy
myrc-h58kj 1/1 Running 0 7m53s app=swiggy
myrc-mmbts 1/1 Running 0 9s app=swiggy
Step6 : Delete all pods ,see 4s create all pods automatically
[root@ip-10-0-0-22 ~]# kubectl delete pod --all
pod "myrc-g6w5t" deleted
pod "myrc-h58kj" deleted
pod "myrc-mmbts" deleted
[root@ip-10-0-0-22 ~]# kubectl get pods --show-labels
NAME READY STATUS RESTARTS AGE LABELS
myrc-ccctm 1/1 Running 0 4s app=swiggy
myrc-x4slc 1/1 Running 0 4s app=swiggy
myrc-zxwnd 1/1 Running 0 4s app=swiggy
Expose the Pods , Need to create Service file
Step7: Service created
[root@ip-10-0-0-22 ~]# vi service.yaml
[root@ip-10-0-0-22 ~]# cat service.yaml
---
apiVersion: v1
kind: Service
metadata:
name: myservice
spec:
type: LoadBalancer
selector:
app: swiggy
ports:
- port: 80
targetPort: 80
[root@ip-10-0-0-22 ~]# kubectl create -f service.yaml
service/myservice created
Step8: See below stable ip and loadbalancer dns came automatically
--List of services
[root@ip-10-0-0-22 ~]# kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 100.64.0.1 <none> 443/TCP 29m
myservice LoadBalancer 100.66.58.204 ae126a2383e494e72af8aa2c68283098-161964620.eu-west-2.elb.amazonaws.com 80:31062/TCP 52s
Step10: if you want to create more pods, you need modify the replicate count change,
technical we can called pods increasing scalein, decreaing scaleout
[root@ip-10-0-0-22 ~]# vi manifest.yaml
replicas: 5 # Fixed: lowercase and proper spacing
[root@ip-10-0-0-22 ~]# kubectl apply -f manifest.yaml
Warning: resource replicationcontrollers/myrc is missing the kubectl.kubernetes.io/last-applied-configuration annotation which is required by kubectl apply. kubectl apply should only be used on resources created declaratively by either kubectl create --save-config or kubectl apply. The missing annotation will be patched automatically.
replicationcontroller/myrc configured
[root@ip-10-0-0-22 ~]# kubectl get pods --show-labels
NAME READY STATUS RESTARTS AGE LABELS
myrc-6kht8 1/1 Running 0 7m23s app=swiggy
myrc-7pvh6 1/1 Running 0 21s app=swiggy
myrc-88kv4 1/1 Running 0 21s app=swiggy
myrc-jhg8d 1/1 Running 0 7m23s app=swiggy
myrc-ljcpb 1/1 Running 0 7m23s app=swiggy
Step11: Decrease Scaledown
[root@ip-10-0-0-22 ~]# vi manifest.yaml
[root@ip-10-0-0-22 ~]# kubectl apply -f manifest.yaml
replicationcontroller/myrc configured
[root@ip-10-0-0-22 ~]# kubectl get pods --show-labels
NAME READY STATUS RESTARTS AGE LABELS
myrc-6kht8 1/1 Running 0 10m app=swiggy
myrc-jhg8d 1/1 Running 0 10m app=swiggy
myrc-ljcpb 1/1 Running 0 10m app=swiggy
Step12: Using command also we can increase the pods
[root@ip-10-0-0-22 ~]# kubectl scale rc myrc --replicas 4
replicationcontroller/myrc scaled
[root@ip-10-0-0-22 ~]# kubectl get pods --show-labels
NAME READY STATUS RESTARTS AGE LABELS
myrc-6kht8 1/1 Running 0 13m app=swiggy
myrc-hl89f 1/1 Running 0 5s app=swiggy
myrc-jhg8d 1/1 Running 0 13m app=swiggy
myrc-ljcpb 1/1 Running 0 13m app=swiggy
[root@ip-10-0-0-22 ~]#
Step13: Decrease
[root@ip-10-0-0-22 ~]# kubectl scale rc myrc --replicas 1
replicationcontroller/myrc scaled
[root@ip-10-0-0-22 ~]# kubectl get pods --show-labels
NAME READY STATUS RESTARTS AGE LABELS
myrc-6kht8 1/1 Running 0 14m app=swiggy
Step14: full information of rc ,events
[root@ip-10-0-0-22 ~]# kubectl describe rc myrc
Name: myrc
Namespace: default
Selector: app=swiggy
Labels: app=swiggy
Annotations: <none>
Replicas: 1 current / 1 desired
Pods Status: 1 Running / 0 Waiting / 0 Succeeded / 0 Failed
Pod Template:
Labels: app=swiggy
Containers:
container1:
Image: shaikmustafa/cycle
Port: 80/TCP
Host Port: 0/TCP
Environment: <none>
Mounts: <none>
Volumes: <none>
Node-Selectors: <none>
Tolerations: <none>
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal SuccessfulCreate 32m replication-controller Created pod: myrc-g6w5t
Normal SuccessfulCreate 32m replication-controller Created pod: myrc-bvch9
Normal SuccessfulCreate 32m replication-controller Created pod: myrc-h58kj
Normal SuccessfulCreate 26m replication-controller Created pod: myrc-mmbts
Normal SuccessfulCreate 23m replication-controller Created pod: myrc-ccctm
Normal SuccessfulCreate 23m replication-controller Created pod: myrc-x4slc
Normal SuccessfulCreate 23m replication-controller Created pod: myrc-zxwnd
Normal SuccessfulCreate 15m replication-controller Created pod: myrc-ljcpb
Normal SuccessfulCreate 15m replication-controller Created pod: myrc-6kht8
Normal SuccessfulDelete 4m39s replication-controller Deleted pod: myrc-88kv4
Normal SuccessfulDelete 4m39s replication-controller Deleted pod: myrc-7pvh6
Normal SuccessfulCreate 2m9s (x4 over 15m) replication-controller (combined from similar events): Created pod: myrc-hl89f
Normal SuccessfulDelete 75s replication-controller Deleted pod: myrc-hl89f
Normal SuccessfulDelete 75s replication-controller Deleted pod: myrc-jhg8d
Normal SuccessfulDelete 75s replication-controller Deleted pod: myrc-ljcpb
Advantage :replicate and scaling
Drawback if this: it is equality based selector, not setbase selector
For ex:- Equality based selector app: swiggy
Set based selector app in swiggy ,zamoto
RC : at time we can access single label, to over come this issue need to use RS(ReplicateSet)
replicaSet
New version of Kuberenets
Step1: Delete the existing my rc
[root@ip-10-0-0-22 ~]# kubectl delete rc myrc
replicationcontroller "myrc" deleted
[root@ip-10-0-0-22 ~]# kubectl get rc
No resources found in default namespace.
--To Check rs version apps/v1
[root@ip-10-0-0-22 ~]# kubectl api-resources | grep -i "rs"
NAME SHORTNAMES APIVERSION NAMESPACED KIND
persistentvolumeclaims pvc v1 true PersistentVolumeClaim
persistentvolumes pv v1 false PersistentVolume
replicationcontrollers rc v1 true ReplicationController
replicasets rs apps/v1 true ReplicaSet
horizontalpodautoscalers hpa autoscaling/v2 true HorizontalPodAutoscaler
csidrivers storage.k8s.io/v1 false CSIDriver
Step2:
[root@ip-10-0-0-22 ~]# vi manifest.yaml
[root@ip-10-0-0-22 ~]# cat manifest.yaml
---
apiVersion: apps/v1
kind: ReplicaSet
metadata:
name: myrs
spec:
replicas: 2 # Fixed: lowercase and proper spacing
selector: # Proper selector definition
matchLabels:
app: swiggy
template: # Moved to top-level under spec
metadata:
labels:
app: swiggy # Must match selector
spec:
containers:
- name: container1
image: shaikmustafa/cycle
ports:
- containerPort: 80
[root@ip-10-0-0-22 ~]# kubectl create -f manifest.yaml
replicaset.apps/myrs created
[root@ip-10-0-0-22 ~]# kubectl get rs
NAME DESIRED CURRENT READY AGE
myrs 2 2 2 97s
[root@ip-10-0-0-22 ~]# kubectl get pods --show-labels
NAME READY STATUS RESTARTS AGE LABELS
myrs-dzz9s 1/1 Running 0 2m53s app=swiggy
myrs-hqdpj 1/1 Running 0 2m53s app=swiggy
Command scaling
Step3: Scalein
[root@ip-10-0-0-22 ~]# kubectl scale rs myrs --replicas 4
replicaset.apps/myrs scaled
[root@ip-10-0-0-22 ~]# kubectl get pods --show-labels
NAME READY STATUS RESTARTS AGE LABELS
myrs-dzz9s 1/1 Running 0 4m33s app=swiggy
myrs-fjddd 1/1 Running 0 4s app=swiggy
myrs-hqdpj 1/1 Running 0 4m33s app=swiggy
myrs-zw2mp 1/1 Running 0 4s app=swiggy
Step4:Scaleout
[root@ip-10-0-0-22 ~]# kubectl scale rs myrs --replicas 1
replicaset.apps/myrs scaled
[root@ip-10-0-0-22 ~]# kubectl get pods --show-labels
NAME READY STATUS RESTARTS AGE LABELS
myrs-dzz9s 1/1 Running 0 4m51s app=swiggy
Full information of the RS
[root@ip-10-0-0-22 ~]# kubectl describe rs myrs
Name: myrs
Namespace: default
Selector: app=swiggy
Labels: <none>
Annotations: <none>
Replicas: 1 current / 1 desired
Pods Status: 1 Running / 0 Waiting / 0 Succeeded / 0 Failed
Pod Template:
Labels: app=swiggy
Containers:
container1:
Image: shaikmustafa/cycle
Port: 80/TCP
Host Port: 0/TCP
Environment: <none>
Mounts: <none>
Volumes: <none>
Node-Selectors: <none>
Tolerations: <none>
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal SuccessfulCreate 7m replicaset-controller Created pod: myrs-hqdpj
Normal SuccessfulCreate 7m replicaset-controller Created pod: myrs-dzz9s
Normal SuccessfulCreate 2m31s replicaset-controller Created pod: myrs-zw2mp
Normal SuccessfulCreate 2m31s replicaset-controller Created pod: myrs-fjddd
Normal SuccessfulDelete 2m12s replicaset-controller Deleted pod: myrs-fjddd
Normal SuccessfulDelete 2m12s replicaset-controller Deleted pod: myrs-hqdpj
Normal SuccessfulDelete 2m12s replicaset-controller Deleted pod: myrs-zw2mp
Drawback
manual scaling here no autscaling ,rollback, exist dowtime it will take some time delay to create pods
Deployment :
Replica, manual scaling ,SBS, nodowntime
Step1:
[root@ip-10-0-0-22 ~]# cat manifest.yaml
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: mydeploy
spec:
replicas: 2 # Fixed: lowercase and proper spacing
selector: # Proper selector definition
matchLabels:
app: swiggy
template: # Moved to top-level under spec
metadata:
labels:
app: swiggy # Must match selector
spec:
containers:
- name: container1
image: shaikmustafa/cycle
ports:
Step2:
Deployment create successfully
[root@ip-10-0-0-22 ~]# kubectl create -f manifest.yaml
deployment.apps/mydeploy created
below both are same
[root@ip-10-0-0-22 ~]# kubectl get rs
NAME DESIRED CURRENT READY AGE
mydeploy-5fc87dd57b 2 2 2 17s
[root@ip-10-0-0-22 ~]# kubectl get deploy
NAME READY UP-TO-DATE AVAILABLE AGE
mydeploy 2/2 2 2 40s
Step3:
[root@ip-10-0-0-22 ~]# kops get cluster
NAME CLOUD ZONES
kopsclstr.k8s.local aws eu-west-2a,eu-west-2b
[root@ip-10-0-0-22 ~]# kops delete cluster --name kopsclstr.k8s.local --yes
Deleted kubectl config for kopsclstr.k8s.local
Deleted cluster: "kopsclstr.k8s.local"
Based on if you learn one ReplicateController remaing all are similar, RS,Deployment
Deamonset ,stateful
Sofar 5 manifest file learned(pods,service,rc,rs,deployment) total 9
Reference Document:
https://mustafa-k8s.hashnode.dev/replication-controller-vs-replica-set
--Thanks
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