Kubernetes

Useful

alias:

alias k="kubectl"
alias ks="kubectl --namespace kube-system"
alias ke="kubectl get events --sort-by='{.lastTimestamp}'"

dump all :

kubectl get all --export=true -o yaml

list form:

k get pods
k get rs # replica set
k get rc # replication controller

what are all the things ?

kubectl api-resources

event sorted by time

kubectl get events --sort-by=.metadata.creationTimestamp

what storage classes does my cluster support?

k get storageclass

audit: who tried to do what?

ks get pod | grep kube-apiserver-ip

ks logs $podname

who tried to scale unsuccessfully?

ks logs $podname | grep scale | grep cloud | awk '$8!=200{print $0}'

Where is the service account token that I gave this pod?

It's in here: /var/run/secrets/kubernetes.io/serviceaccount/token

Scripting Scaling

Manually edit the replicas of a deployment from within the same namespace, but in a different pod:

give the actor pod a service account ( possibly via it's deployment ).
create a Role as below.
create the RoleBinding to connect the ServiceAccount to the Role.

Now you have: Pod -> Deployment -> ServiceAccount -> RoleBinding -> Role

Now the Pod has permission to do what it needs. Very similar to AWS's "IAM Role" where you give an instance a role that has the permissions that it needs to operate.

Note that in this case "ClusterRole" and ClusterRoleBinding are not required. It's all namespaced to the namespace that your deployment is in. In this case: "default".

export API_URL="https://${KUBERNETES_SERVICE_HOST}:${KUBERNETES_SERVICE_PORT}/${KUBE_ENDPOINT}"
export TOKEN=`cat /var/run/secrets/kubernetes.io/serviceaccount/token`
export CURL_CA_BUNDLE=/var/run/secrets/kubernetes.io/serviceaccount/ca.crt

curl \
 -H 'Accept: application/json' \
 -H "Authorization: Bearer $TOKEN" \
 $API_URL \
 > scale.json
# edit scale.json, set replicas to 4
curl -X PUT \
 -d@scale.json \
 -H 'Content-Type: application/json' \
 -H "Authorization: Bearer $TOKEN" \
 $API_URL

CURL_CA_BUNDLE - kubenerets is it's own CA, and presennts to each pod a ca bundle that makes ssl "in" the cluster valid.

This was the role that did it. FIXME: pare it down

apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: kube-cloudwatch-autoscaler
  labels:
    app: kube-cloudwatch-autoscaler
rules:
- apiGroups:
  - ""
  resources:
  - nodes
  verbs:
  - list
- apiGroups:
  - apps
  resources:
  - deployments
  - deployments.apps
  - deployments.apps/scale
  - "*/scale"
  verbs:
  - get
  - update
  - patch
  - put
- apiGroups:
  - ""
  resources:
  - configmaps
  verbs:
  - get
  - create

On patching

There are a couple of way to change an object.

export TOKEN=`cat /var/run/secrets/kubernetes.io/serviceaccount/token`
export CURL_CA_BUNDLE=/var/run/secrets/kubernetes.io/serviceaccount/ca.crt

1. dump whole "thing" , make change post object back ( as above ) GET -> PUT

curl \
 -v \
 -H 'Accept: application/json' \
 -H "Authorization: Bearer $TOKEN" \
 $API_URL \
 > scale.json
# edit scale.json, set replicas to 4
curl -X PUT \
 -d@scale.json \
 -H 'Content-Type: application/json' \
 -H "Authorization: Bearer $TOKEN" \
 $API_URL

2. terse PATCH

curl -sS \
 -X 'PATCH' \
 -H "Authorization: Bearer ${TOKEN}" \
 -H 'Content-Type: application/merge-patch+json' \
 $API_URL \
 -d '{"spec": {"replicas":  1}}'

3. old / full PATCH ?

reference: https://stackoverflow.com/questions/41792851/manage-replicas-count-for-deployment-using-kubernetes-api ( 1 year 8 months old at tie of _this_ writing )

Careful, compare:

BORKEN!

PAYLOAD='[{"op":"replace","path":"/spec/replicas","value":"3"}]'
curl \
 -X PATCH \
 -d ${PAYLOAD} \
 -H 'Content-Type: application/json-patch+json' \
 -H "Authorization: Bearer ${TOKEN}" \
 $API_URL

WERKS!

curl \
 -X PATCH \
 -d '[{"op":"replace","path":"/spec/replicas","value":3}]' \
 -H 'Content-Type: application/json-patch+json' \
 -H "Authorization: Bearer ${TOKEN}" \
 $API_URL

Closely:

-d '[{"op":"replace","path":"/spec/replicas","value":"3"}]'  <- broken
-d '[{"op":"replace","path":"/spec/replicas","value":3}]' <- works

Template examples

kubectl get no -o go-template='Template:Range .itemsTemplate:.metadata.name Template:.spec.externalIDTemplate:"\n"Template:End'

metricss

wget "$(kubectl config view -o jsonpath='{range .clusters[*]}{@.cluster.server}{"\n"}{end}')"

Practices and Guidlines

Do not use replication controllers, instead use replica sets

Cgroup / slice errors

https://github.com/kubernetes/kubernetes/issues/56850

log message:

Sep 18 21:32:37 ip-10-10-37-50 kubelet[1681]: E0918 21:32:37.901058    1681 summary.go:92] Failed to get system container stats for "/system.slice/docker.service": failed to get cgroup stats for "/system.slice/docker.service": failed to get container info for "/system.slice/docker.service": unknown container "/system.slice/docker.service"