Kubernetes: how to scale my pods

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> 

Example

# kubectl scale --replicas=3 deployment xyz 

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).