Kubernetes

Advanced Usage

Network Policy

Network Policy

Network Policy

Similar to Firewalls

Deny Ingress / Egress traffic

Use Label Selectors & IP blocks

Init Containers

Advanced Usage

Init Containers

Advanced Usage

apiVersion: v1
kind: Pod
spec:
  initContainers:
  - name: init-db
    image: busybox
    command: ['sh', '-c', 'until nslookup db; do sleep 2; done;']
  containers:
  - name: myapp-container
    image: busybox
    command: ['sh', '-c', 'echo The app is running! && sleep 3600']

Init Containers

Advanced Usage

POD

Init Containers

Advanced Usage

POD

init-db

Init Containers

Advanced Usage

POD

init-db

Init Containers

Advanced Usage

POD

init-db

Init Containers

Advanced Usage

POD

init-db

Init Containers

Advanced Usage

POD

my-app

Init Containers

Ensure Services are available

Ensure Volumes are populated

Node Affinity

kubectl label nodes \
    <node-name> \
    <label-key>=<label-value>

Node Affinity

kubectl label nodes \
    my-node-1 \
    gpu=nvidia-tesla-p100

Node Affinity

requiredDuringSchedulingIgnoredDuringExecution
preferredDuringSchedulingIgnoredDuringExecution
In Pod's spec.affinity.nodeAffinity:

Node Affinity

requiredDuringSchedulingIgnoredDuringExecution
preferredDuringSchedulingIgnoredDuringExecution

HARD RULES

SOFT RULES

In Pod's spec.affinity.nodeAffinity:

Node Selection

kubectl label nodes <node-name> <label-key>=<label-value>
apiVersion: v1
kind: Pod
metadata:
  name: nginx
spec:
  containers:
  - name: nginx
    image: nginx
  nodeSelector:
    disktype: ssd

Recap: Services

Service
Type: ClusterIP

10.47.240.1:80
my-app-1h4md
label selection
my-app.my-ns.svc.cluster.local
10.47.242.240:8080
10.47.242.241:8080
10.47.242.242:8080
my-app-j2vek
my-app-xt8lx

Recap: Services

my-app-1h4md.my-app.my-ns.svc.cluster.local
my-app-xt81x.my-app.my-ns.svc.cluster.local
10.47.242.240:8080
10.47.242.241:8080
10.47.242.242:8080
Headless Service

(clusterIP: None)

my-app-1h4md
my-app-j2vek
my-app-xt8lx
my-app-j2vek.my-app.my-ns.svc.cluster.local

Recap: Services

my-app-1h4md.my-app.my-ns.svc.cluster.local
my-app-xt81x.my-app.my-ns.svc.cluster.local
10.47.242.240:8080
10.47.242.241:8080
10.47.242.242:8080
Headless Service

(clusterIP: None)

my-app-1h4md
my-app-j2vek
my-app-xt8lx
my-app-j2vek.my-app.my-ns.svc.cluster.local

StatefulSets

A deployment with extra guarantees:

StatefulSets

A deployment with extra guarantees:

my-app-1h4md
my-app-j2vek
my-app-xt8lx
my-app-2
my-app-1
my-app-0

DEPLOYMENT

STATEFULSET

StatefulSets

A deployment with extra guarantees:

  • Stable, unique network identifiers.

StatefulSets

A deployment with extra guarantees:

  • Stable, unique network identifiers.

my-app-2
my-app-1

STATEFULSET

my-app-0.my-app.my-ns.svc.cluster.local
my-app-2.my-app.my-ns.svc.cluster.local
Headless Service

my-app-1.my-app.my-ns.svc.cluster.local
my-app-0

StatefulSets

A deployment with extra guarantees:

  • Stable, unique network identifiers.

  • Stable, persistent storage.

StatefulSets

A deployment with extra guarantees:

  • Stable, unique network identifiers.

  • Stable, persistent storage.

  • Ordered, graceful deployment and scaling.

  • Ordered, graceful deletion and termination.

  • Ordered, automated rolling updates.

StatefulSets

A deployment with extra guarantees:

  • Stable, unique network identifiers.

  • Stable, persistent storage.

  • Ordered, graceful deployment and scaling.

  • Ordered, graceful deletion and termination.

  • Ordered, automated rolling updates.

my-app-0
my-app-1
my-app-2
Created
Created
Created

Apache Zookeeper

Distributed State Management

Apache Zookeeper

Distributed State Management

/
/Znode1

Value: "foo"
/Znode2

Value: "bar"
/Znode1/subnode

Value: "foo"
/Znode2/hello

Value: "world"
/Znode2/mutex

Value: "locked"

Apache Zookeeper

Distributed State Management

DEMO

POD DISRUPTION BUDGET

POD DISRUPTION BUDGET

my-app-2
my-app-0
my-app-0
apiVersion: policy/v1beta1
kind: PodDisruptionBudget
metadata:
  name: zk-pdb
spec:
  selector:
    matchLabels:
      app: zk
  maxUnavailable: 2

POD DISRUPTION BUDGET

my-app-2
my-app-0
my-app-0
apiVersion: policy/v1beta1
kind: PodDisruptionBudget
metadata:
  name: zk-pdb
spec:
  selector:
    matchLabels:
      app: zk
  maxUnavailable: 2

Taints & Tolerations

Taints & Tolerations

Opposite of NodeAffinity

Taints & Tolerations

# To add the NoSchedule taint
kubectl taint nodes worker-1 key=value:NoSchedule

 

# To remove the taint
kubectl taint nodes worker-1 key:NoSchedule-

Taints & Tolerations

# In a PodSpec
tolerations:
- key: "key"
  operator: "Equal"
  value: "value"
  effect: "NoSchedule"

Taints & Tolerations

# In a PodSpec
tolerations:
- key: "key"
  operator: "Equal"
  value: "value"
  effect: "NoSchedule"

Effects:

- NoSchedule

- PreferNoSchedule

- NoExecute

Taints & Tolerations

https://kubernetes.io/docs/concepts/configuration/taint-and-toleration/#taint-based-evictions

Builtins

These get applied automatically by NodeController

Taints & Tolerations

https://kubernetes.io/docs/concepts/configuration/taint-and-toleration/#taint-based-evictions

Builtins

These get applied automatically by NodeController

RBAC

RBAC

Role: Single Namespace

ClusterRole: All Namespaces

RBAC

Role: Single Namespace

ClusterRole: All Namespaces

ONLY additive

RBAC

When a resource needs access to other resources

 

E.G. Operators

RBAC

# Allows User to get all pods

kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  namespace: default
  name: pod-reader
rules:
- apiGroups: [""] # "" indicates the core API group
  resources: ["pods"]
  verbs: ["get", "watch", "list"]

RoleBinding / ClusterRoleBinding

RoleBinding / ClusterRoleBinding

users:
- name: corey
  user:
    client-certificate: <xxx>
    client-key: <xxx>
Role

RoleBinding / ClusterRoleBinding

users:
- name: corey
  user:
    client-certificate: <xxx>
    client-key: <xxx>
Role

https://github.com/coreos/dex/blob/master/Documentation/kubernetes.md

RoleBinding / ClusterRoleBinding

# This role binding allows "jane" to read pods in the "default" namespace.
kind: RoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: read-pods
  namespace: default
subjects:
- kind: User
  name: jane
  apiGroup: rbac.authorization.k8s.io
roleRef:
  kind: Role
  name: pod-reader # this must match the name of the Role
  apiGroup: rbac.authorization.k8s.io

RoleBinding / ClusterRoleBinding

# This cluster role binding allows anyone in the "manager" group 
# to read secrets in any namespace.
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: read-secrets-global
subjects:
- kind: Group
  name: manager
  apiGroup: rbac.authorization.k8s.io
roleRef:
  kind: ClusterRole
  name: secret-reader
  apiGroup: rbac.authorization.k8s.io

RoleBinding / ClusterRoleBinding

# This cluster role binding allows anyone in the "manager" group 
# to read secrets in any namespace.
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: read-secrets-global
subjects:
- kind: Group
  name: manager
  apiGroup: rbac.authorization.k8s.io
roleRef:
  kind: ClusterRole
  name: secret-reader
  apiGroup: rbac.authorization.k8s.io

FIN

K8s Advanced Usage

By Corey Brooks

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K8s Advanced Usage

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