Deployment
How do you upgrade your application/pod
rolling update
----------------
rollback
pods are deployed using replication controller or replicaset
Deployment allow upgrade/undo changes.
how do create deployment
- it is similar to replicaset
> cat deployment-def.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: myapp-deployment
labels:
app: myapp
type: front-end
spec:
template:
metadata:
name: myapp-pod
labels:
app: myapp
type: front-end
spec:
containers:
- name: nginx-container
image: nginx
replicas: 3
selector:
metchLabels:
type: front-end
> kc create -f deployment-def.yaml
display newly created deployment
> kc get deployment
deployment automatically creates replicaSets in the name of deployment
> kc get rs
replica sets creates pod
> kc get pods
you will see name of the pod with name of deployment and replicaset.
deployment creates new object called deployment whch allow you to update, upgrade, and manage replica set and undo the change.
summary
------------
> kc get all
you will see deployment, replica set and pods it created.
Certification Tip!
Creating yaml file manually is a bit of challenging. the best option to use kc run command followed by name of the pod and name of the image.
for eg, to create a pod with httpd image
> kc run http --image=httpd
> kc run nginx --image=nginx
to create a manifest (yaml) file, use the option --dry-run. it will not create pod but generates yaml file
> kc run nginx --image=nginx --dry-run=client -o yaml
Create a deployment
> kc create deployment --image=nginx nginx
generate deployment yaml file. As we know --dry-run will not create deployment
> kc create deployment nginx --image=nginx --dry-run=client =o yaml
add 4 replicas (--replicas=4) on above command
> kc create deployment nginx --image=nginx --dry-run=client -o yaml > nginx.deploy.yaml
edit the output file and change the replicas to 4.
once file is modified, create the deployment.
https://kubernetes.io/docs/reference/kubectl/conventions/
LAB
-----------
1. How many PODs exist on the system in the current(default) namespace?
controlplane $ alias kc=kubectl
controlplane $ kc get po
No resources found in default namespace.
controlplane $
2. How many ReplicaSets exist on the system in the current(default) namespace?
controlplane $ kc get rs
No resources found in default namespace.
controlplane $ kc get replicasets
No resources found in default namespace.
controlplane $
hint: Run the command 'kubectl get replicaset' and count the number of ReplicaSets.
3. How many Deployments exist on the system in the current(default) namespace?
controlplane $ kc get deployment
No resources found in default namespace.
controlplane $ kc get ns
NAME STATUS AGE
default Active 4m2s
kube-node-lease Active 4m4s
kube-public Active 4m4s
kube-system Active 4m4s
hints: Run the command 'kubectl get deployment' and count the number of Deployments.
4. How many Deployments exist on the system now?
We just created a Deployment! Check again!
controlplane $ kc get deployment
NAME READY UP-TO-DATE AVAILABLE AGE
frontend-deployment 0/4 4 0 18s
controlplane $
Hint: Run the command 'kubectl get deployment' and count the number of deployments.
5. How many ReplicaSets exist on the system now?
controlplane $ kc get rs
NAME DESIRED CURRENT READY AGE
frontend-deployment-56d8ff5458 4 4 0 77s
controlplane $
Hint: Run the command 'kubectl get replicaset' and count the number of ReplicaSets.
6. How many PODs exist on the system now?
controlplane $ kc get rs
NAME DESIRED CURRENT READY AGE
frontend-deployment-56d8ff5458 4 4 0 77s
controlplane $ kc get po
NAME READY STATUS RESTARTS AGE
frontend-deployment-56d8ff5458-7mhgl 0/1 ImagePullBackOff 0 2m12s
frontend-deployment-56d8ff5458-t829q 0/1 ImagePullBackOff 0 2m12s
frontend-deployment-56d8ff5458-wt8bg 0/1 ErrImagePull 0 2m12s
frontend-deployment-56d8ff5458-zkjq9 0/1 ImagePullBackOff 0 2m12s
controlplane $
7. Out of all the existing PODs, how many are ready?
Looking at the output above, ready is = 0
hint: Run the command 'kubectl get deployment' and count the number of PODs.
8. What is the image used to create the pods in the new deployment?
> kc describe deployment frontend-deployment | grep -i image
image: busybox888
controlplane $ kc get rs
NAME DESIRED CURRENT READY AGE
frontend-deployment-56d8ff5458 4 4 0 4m1s
controlplane $ kc describe rs frontend-deployment-56d8ff5458
Name: frontend-deployment-56d8ff5458
Namespace: default
Selector: name=busybox-pod,pod-template-hash=56d8ff5458
Labels: name=busybox-pod
pod-template-hash=56d8ff5458
Annotations: deployment.kubernetes.io/desired-replicas: 4
deployment.kubernetes.io/max-replicas: 5
deployment.kubernetes.io/revision: 1
Controlled By: Deployment/frontend-deployment
Replicas: 4 current / 4 desired
Pods Status: 0 Running / 4 Waiting / 0 Succeeded / 0 Failed
Pod Template:
Labels: name=busybox-pod
pod-template-hash=56d8ff5458
Containers:
busybox-container:
Image: busybox888
Port: <none>
Host Port: <none>
Command:
sh
-c
echo Hello Kubernetes! && sleep 3600
Environment: <none>
Mounts: <none>
Volumes: <none>
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal SuccessfulCreate 4m32s replicaset-controller Created pod: frontend-deployment-56d8ff5458-7mhgl
Normal SuccessfulCreate 4m32s replicaset-controller Created pod: frontend-deployment-56d8ff5458-wt8bg
Normal SuccessfulCreate 4m32s replicaset-controller Created pod: frontend-deployment-56d8ff5458-t829q
Normal SuccessfulCreate 4m32s replicaset-controller Created pod: frontend-deployment-56d8ff5458-zkjq9
controlplane $
hint: Run the command 'kubectl describe deployment' and look under the containers section.
9. Why do you think the deployment is not ready?
> kc get pods
> kc describe pod <nameof the pod>
looking at the output above,
- image busybox88 does not exist
failed to pull the image. rpc error so repo may not be available.
10. Create a new Deployment using the 'deployment-definition-1.yaml' file located at /root/
There is an issue with the file, so try to fix it.
Name: deployment-1
cat deployment-def.yaml
---
apiVersion: apps/v1
kind: deployment
metadata:
name: deployment-1
spec:
replicas: 2
selector:
matchLabels:
name: busybox-pod
template:
metadata:
labels:
name: busybox-pod
spec:
containers:
- name: busybox-container
image: busybox888
command:
- sh
- "-c"
- echo Hello Kubernetes! && sleep 3600
controlplane $ kc create -f deployment-definition-1.yaml
Error from server (BadRequest): error when creating "deployment-definition-1.yaml": deployment in version "v1" cannot be handled as a Deployment: no kind "deployment" is registered for version "apps/v1" in scheme "k8s.io/kubernetes/pkg/api/legacyscheme/scheme.go:30"
controlplane $
change Kind: deployment to Deployment - first letter uppercase
controlplane $ kc create -f deployment-definition-1.yaml
deployment.apps/deployment-1 created
controlplane $
11. Create a new Deployment with the below attributes using your own deployment definition file
Name: httpd-frontend; Replicas: 3; Image: httpd:2.4-alpine
Name: httpd-frontend
Replicas: 3
Image: httpd:2.4-alpine
> kc create deploymetn http-frontend; replicas=3 --image=httpd:2.4-alpine
or
> kc create deployment httpd-frontend --image=httpd:2.4-alpine
> kc scale deployment --replicas=3 httpd-frontend
> kc get deployment httpd-frontend
or
do it manually
apiVersion: apps/v1
kind: Deployment
metadata:
name: httpd-frontend-deployment
spec:
replicas: 3
selector:
matchLabels:
name: httpd-frontend
template:
metadata:
labels:
name: httpd-frontend
spec:
containers:
- name: httpd-frontend
image: httpd:2.4-alpine
controlplane $ kc create -f mydep.yaml
deployment.apps/httpd-frontend created
controlplane $ kc get deploy
NAME READY UP-TO-DATE AVAILABLE AGE
deployment-1 0/2 2 0 9m31s
frontend-deployment 0/4 4 0 21m
httpd-frontend 3/3 3 3 8s
controlplane $ cat mydep.yaml
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: httpd-frontend
spec:
replicas: 3
selector:
matchLabels:
name: httpd-frontend
template:
metadata:
labels:
name: httpd-frontend
spec:
containers:
- name: httpd-frontend
image: httpd:2.4-alpine
controlplane $
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