Kubernetes: how to scale my pods - kubernetes

Question

I'm new to Kubernetes. I try to scale my pods. First I started 3 pods:
./cluster/kubectl.sh run my-nginx --image=nginx --replicas=3 --port=80
There were starting 3 pods. First I tried to scale up/down by using a replicationcontroller but this did not exist. It seems to be a replicaSet now.
./cluster/kubectl.sh get rs
NAME DESIRED CURRENT AGE
my-nginx-2494149703 3 3 9h
I tried to change the amount of replicas described in my replicaset:
./cluster/kubectl.sh scale --replicas=5 rs/my-nginx-2494149703
replicaset "my-nginx-2494149703" scaled
But I still see my 3 original pods
./cluster/kubectl.sh get pods
NAME READY STATUS RESTARTS AGE
my-nginx-2494149703-04xrd 1/1 Running 0 9h
my-nginx-2494149703-h3krk 1/1 Running 0 9h
my-nginx-2494149703-hnayu 1/1 Running 0 9h
I would expect to see 5 pods.
./cluster/kubectl.sh describe rs/my-nginx-2494149703
Name: my-nginx-2494149703
Namespace: default
Image(s): nginx
Selector: pod-template-hash=2494149703,run=my-nginx
Labels: pod-template-hash=2494149703
run=my-nginx
Replicas: 3 current / 3 desired
Pods Status: 3 Running / 0 Waiting / 0 Succeeded / 0 Failed
Why isn't it scaling up? Do I also have to change something in the deployment?
I see something like this when I describe my rs after scaling up:
(Here I try to scale from one running pod to 3 running pods). But it remains one running pod. The other 2 are started and killed immediatly
34s 34s 1 {replicaset-controller } Normal SuccessfulCreate Created pod: my-nginx-1908062973-lylsz
34s 34s 1 {replicaset-controller } Normal SuccessfulCreate Created pod: my-nginx-1908062973-5rv8u
34s 34s 1 {replicaset-controller } Normal SuccessfulDelete Deleted pod: my-nginx-1908062973-lylsz
34s 34s 1 {replicaset-controller } Normal SuccessfulDelete Deleted pod: my-nginx-1908062973-5rv8u

Answer 1

This is working for me
kubectl scale --replicas=<expected_replica_num> deployment <deployment_label_name> -n <namespace>
Example
# kubectl scale --replicas=3 deployment xyz -n my_namespace

Answer 2

TL;DR: You need to scale your deployment instead of the replica set directly.
If you try to scale the replica set, then it will (for a very short time) have a new count of 5. But the deployment controller will see that the current count of the replica set is 5 and since it knows that it is supposed to be 3, it will reset it back to 3. By manually modifying the replica set that was created for you, you are fighting with the system controller (which is untiring and will pretty much always outlast you).

Answer 3

kubectl run my-nginx --image=nginx --replicas=3 --port=80 in this kubectl run will create a deployment or job to manage the created container(s).
Deployment-->ReplicaSet-->Pod this is how kubernetes works.
If you change the bottom-level object, its higher-level object will undo your change.You have to change the top-level object.

Answer 4

scale it down to zero and then to the number of pods you required (guess it equals to 3)
kubectl scale deployment <deployment-name> --replicas=0 -n <namespace>
kubectl scale deployment <deployment-name> --replicas=3 -n <namespace>

Answer 5

Not sure if this is the best way as I'm starting out with kubernetes, but I did this by updating my yaml file
# app.yaml
apiVersion: apps/v1
...
spec:
replicas: <new value>
and running $ kubectl scale -f app.yaml --replicas=<new value>
you can verify your new number of replicas by running $ kubectl get pods
In my case I was also interested in scaling back my VMs, on google cloud. I did this with $ gcloud container clusters resize appName --size=1 --zone "my-zone"

Answer 6

Below example shows how you should scale up/down your "pods/resource/deployments".
k8smaster#k8smaster:~/debashish$ more createdeb_deployment1.yaml
---
apiVersion: apps/v1beta2
kind: Deployment
metadata:
name: debdeploy-webserver
spec:
replicas: 1
selector:
matchLabels:
app: debdeploy1webserver
template:
metadata:
labels:
app: debdeploy1webserver
spec:
containers:
-
image: "docker.io/debu3645/debapachewebserver:v1"
name: deb-deploy1-container
ports:
-
containerPort: 6060
deployment created -->
**kubectl -n debns1 create -f createdeb_deployment1.yaml**
k8smaster#k8smaster:~/debashish$ `kubectl scale --replicas=5 **deployment**/debdeploy-webserver -n debns1`
(Scale up 5 deployments)
k8smaster#k8smaster:~/debashish$ kubectl get pods -n debns1
NAME READY STATUS RESTARTS AGE
debdeploy-webserver-7cf4fb74c5-8wvzx 1/1 Running 0 16s
debdeploy-webserver-7cf4fb74c5-jrf6v 1/1 Running 0 16s
debdeploy-webserver-7cf4fb74c5-m9fpw 1/1 Running 0 16s
debdeploy-webserver-7cf4fb74c5-q9n7r 1/1 Running 0 16s
debdeploy-webserver-7cf4fb74c5-ttw6p 1/1 Running 1 19h
resourcepod-deb1 1/1 Running 5 6d18h
k8smaster#k8smaster:~/debashish$ **kubectl get ep -n debns1**
NAME ENDPOINTS AGE
frontend-svc-deb 192.168.1.10:80,192.168.1.11:80,192.168.1.12:80 + 2 more... 18h
frontend-svc1-deb 192.168.1.8:80 14d
frontend-svc2-deb 192.168.1.8:80 5d19h
k8smaster#k8smaster:~/debashish$ **kubectl scale --replicas=2** deployment/debdeploy-webserver -n debns1
(Scale down from 5 to 2)
deployment.extensions/debdeploy-webserver scaled
k8smaster#k8smaster:~/debashish$ **kubectl get pods -n debns1**
NAME READY STATUS RESTARTS AGE
debdeploy-webserver-7cf4fb74c5-8wvzx 1/1 Terminating 0 35m
debdeploy-webserver-7cf4fb74c5-jrf6v 1/1 Terminating 0 35m
debdeploy-webserver-7cf4fb74c5-m9fpw 1/1 Terminating 0 35m
debdeploy-webserver-7cf4fb74c5-q9n7r 1/1 Running 0 35m
debdeploy-webserver-7cf4fb74c5-ttw6p 1/1 Running 1 19h
resourcepod-deb1 1/1 Running 5 6d19h
k8smaster#k8smaster:~/debashish$ **kubectl get pods -n debns1**
NAME READY STATUS RESTARTS AGE
debdeploy-webserver-7cf4fb74c5-q9n7r 1/1 Running 0 37m
debdeploy-webserver-7cf4fb74c5-ttw6p 1/1 Running 1 19h
resourcepod-deb1 1/1 Running 5 6d19h
k8smaster#k8smaster:~/debashish$ kubectl **scale --current-replicas=4 --replicas=2** deployment/debdeploy-webserver -n debns1 (Check the current no. of deployments. If current replication is 4, then bring it down to 2, else dont do anything)
error: Expected replicas to be 4, was 2
k8smaster#k8smaster:~/debashish$ **kubectl scale --current-replicas=3 --replicas=10 deployment/debdeploy-webserver -n debns1**
error: Expected replicas to be 3, was 2
k8smaster#k8smaster:~/debashish$ **kubectl scale --current-replicas=2 --replicas=10 deployment/debdeploy-webserver -n debns1**
deployment.extensions/debdeploy-webserver scaled
k8smaster#k8smaster:~/debashish$ **kubectl get pods -n debns1**
NAME READY STATUS RESTARTS AGE
debdeploy-webserver-7cf4fb74c5-46bxg 1/1 Running 0 6s
debdeploy-webserver-7cf4fb74c5-d6qsx 0/1 ContainerCreating 0 6s
debdeploy-webserver-7cf4fb74c5-fdq6v 1/1 Running 0 6s
debdeploy-webserver-7cf4fb74c5-gd87t 1/1 Running 0 6s
debdeploy-webserver-7cf4fb74c5-kqdbj 0/1 ContainerCreating 0 6s
debdeploy-webserver-7cf4fb74c5-q9n7r 1/1 Running 0 47m
debdeploy-webserver-7cf4fb74c5-qjvm6 1/1 Running 0 6s
debdeploy-webserver-7cf4fb74c5-skxq4 0/1 ContainerCreating 0 6s
debdeploy-webserver-7cf4fb74c5-ttw6p 1/1 Running 1 19h
debdeploy-webserver-7cf4fb74c5-wlc7q 0/1 ContainerCreating 0 6s
resourcepod-deb1 1/1 Running 5 6d19h

Answer 7

for deployment
kubectl scale deployment <deployment-name> --replicas=3 -n <namespace>
for statefulset
kubectl scale statefulsets <stateful-set-name> --replicas=3 -n <namespace>