Kubernetes

Useful

alias:

alias k="kubectl"
alias ks="kubectl --namespace kube-system"                                          # Kubernetes Events
alias ke="kubectl get events --sort-by='{.lastTimestamp}'"                          # Kubernetes System stuff
alias kse="kubectl --namespace kube-system get events --sort-by='{.lastTimestamp}'" # Kubernetes Systems Events

dump all :

kubectl get all --export=true -o yaml

( namespace kube-system not dumped )

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

how are pod spread out over nodes:

k describe node | grep -E '(^Non-t|m |^Name)' | more

( doesn't scale well, no indication of )

if you used kops to deploy the cluster then nodes are labes with their instance groups, you can be more specific like this:

k describe node -l kops.k8s.io/instancegroup=<instance group name> | grep -E '(^Non-t|m |^Name)' | more

how many nods in each instance group? ( tested under kops )

for i in `kops get ig 2>/dev/null| grep -v NAME | awk '{print $1}'`
do
echo $i
kubectl get nodes -l kops.k8s.io/instancegroup=$i
done

how many pods per node:

k get pod -o wide | grep -v NAME | awk '{print $8}' | sort | uniq -c | sort -rn

k get pod --all-namespaces -o wide | grep -v NAME | awk '{print $8}' | sort | uniq -c | sort -rn

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:

1. give the actor pod a service account ( possibly via it's deployment ).
2. create a Role as below.
3. 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

list images by pod:

kubectl get pods --all-namespaces -o=jsonpath='{range .items[*]}{"\n"}{.metadata.name}{":\t"}{range .spec.containers[*]}{.image}{", "}{end}{end}{"\n"}'

list images by deploy

kubectl get deploy -o=jsonpath='{range .items[*]}{"\n"}{.metadata.name}{":\t"}{range .spec.template.spec.containers[*]}{.image}{", "}{end}{end}{"\n"}'

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"

MAAS ubuntu

https://stripe.com/blog/operating-kubernetes

https://cloudplatform.googleblog.com/2018/05/Kubernetes-best-practices-Setting-up-health-checks-with-readiness-and-liveness-probes.html

https://medium.com/@adriaandejonge/moving-from-docker-to-rkt-310dc9aec938

https://coreos.com/rkt/docs/latest/rkt-vs-other-projects.html#rkt-vs-docker

https://hackernoon.com/docker-containerd-standalone-runtimes-heres-what-you-should-know-b834ef155426?gi=3c7edac0b22d

Security

Todo / read:

• https://github.com/aquasecurity/kube-hunter/blob/master/README.md
• https://www.arctiq.ca/events/2018/10/5/building-a-secure-container-strategy-with-aqua-security-microsoft-azure-and-hashicorp-vault/

References and Reading

Replica set versus Replication controller

https://www.mirantis.com/blog/kubernetes-replication-controller-replica-set-and-deployments-understanding-replication-options/

Publishing services - service types

https://kubernetes.io/docs/concepts/services-networking/service/#publishing-services-service-types

Kuberenets the hard way

https://github.com/kelseyhightower/kubernetes-the-hard-way

HPA broken

Blue is test

Blue env:

Client Version: v1.12.2
Server Version: v1.10.6

Prod env:

Client Version: v1.12.2
Server Version: v1.9.8

In prod HPAs work. When I ask for them I see:

NAME                        REFERENCE                              TARGETS   MINPODS   MAXPODS   REPLICAS   AGE
adjust                      Deployment/adjust                      0%/70%    1         5         1          1d
web-admin                   Deployment/web-admin                   0%/70%    1         3         1          2h

In blue env they don't work, I see:

NAME                        REFERENCE                              TARGETS   MINPODS   MAXPODS   REPLICAS   AGE
adjust                      Deployment/adjust                      <unknown>/70%    1         5         1          1d
web-admin                   Deployment/web-admin                   <unknown>/70%    1         3         1          2h

in Kubernetes events we see:

HorizontalPodAutoscaler Warning FailedGetResourceMetric horizontal-pod-autoscaler unable to get metrics for resource cpu: no metrics returned from resource metrics API

Note that the metrics server is running in kube-system, but there are no repo files for that in /third-party" in prod.

In blue we store all metrics-server related files in /thirdpary/metrics-server ( taken from git@github.com:kubernetes-incubator/metrics-server.git )

In prod the deployment has:

      - command:
        - /metrics-server
        - --source=kubernetes.summary_api:''

In blue this seemed to do the trick

          - /metrics-server
          - --kubelet-preferred-address-types=InternalIP
          - --kubelet-insecure-tls

Cluster scaling

ks get configmap cluster-autoscaler-status -o yaml

Steps to move hardware around

in this case we are removing the last node from an instance group and then removing the instance group.

Reference: https://kubernetes.io/docs/concepts/architecture/nodes/

1. Cordon the node

k cordon ip-xx-xx-xx-xx.region.compute.internal

No new pods will be deployed here.

2. drain ( move pods here to somewhere else )

k drain ip-xx-xx-xx-xx.region.compute.internal

You may need to add "--ignore-daemonsets" if you have daemonsets running ( data dog , localredis )

You may ned to "--delete-local-data" if you have a metrics server on this node. BE CAREFUL. You will loose metrics, but probably you have an "out of cluster" place where metrics are stored ( datadog, elastic search, etc )

3. remove the nodegroup from the autoscaler:

ks edit deploy cluster-autoscaler

4. tell kops to delete the instance group.

kops delete ig myig

at this point the vms will be shut down.

k get nodes

Also See

• kops - automated kubenetes cluster build.
• What I learned today Nov 2nd 2018