Скачать или смотреть Kubernetes for Beginners - Intro to Advanced - Day 2

*Deployments*
Provides mechanisms for auto-healing; state management.
Maintains replicaSets (It’s a type of resource) and maintains the expected state.
Deployment can contain multiple pods.
deployment.yaml.
Imp. config parameters.
*Service (svc) / Loadbalancer*

SVC acts as load balancer to the deployments

SVC is used to add network to the deployed pods.

abstraction to help you expose groups of Pods over a network.

Service types

Kubernetes offers three primary service types:

*ClusterIP - POD to POD - internal communication*
*Purpose:* Primarily used for internal communication within the cluster.
*Exposure:* Only accessible within the cluster network.
*IP Assignment:* Allocates a virtual IP address within the cluster.
*Use Cases:*
Services that are only consumed by other services within the cluster.
Internal load balancing.
*NodePort - localhost access*
*Purpose:* Exposes services to the nodes in the cluster.
*Exposure:* Accessible from within the cluster and through a static port on each node.
*IP Assignment:* Allocates a static port on each node.
*Use Cases:*
Services that need to be accessed from outside the cluster but don't require a public IP address.
Simple load balancing.
*LoadBalancer - Advanced - Enterprise grade*
*Purpose:* Exposes services to the internet or a corporate network.
*Exposure:* Accessible from the internet or a corporate network.
*IP Assignment:* Creates a load balancer in the cloud provider's infrastructure and assigns a public IP address.
*Use Cases:*
Services that need to be publicly accessible.
Advanced load balancing features (e.g., session affinity, health checks).
Kubectl port-forwarding

`kubectl port-forward svc/my-service 8082:80`

Creating connection from another service

```jsx
apiVersion: apps/v1
kind: Deployment
metadata:
name: ubuntu-deployment
labels:
app: ubuntu
spec:
replicas: 1
selector:
matchLabels:
app: ubuntu
template:
metadata:
labels:
app: ubuntu
spec:
containers:
name: ubuntu
image: ubuntu
command: ["sleep", "123456"]
```


Connection between services.

*ConfigMap*

A ConfigMap is an API object used to store *non-confidential* data in key-value pairs.

[Pods](https://kubernetes.io/docs/concepts/w... consume ConfigMaps as environment variables.

A ConfigMap allows you to decouple environment-specific configuration from your [container images](https://kubernetes.io/docs/reference/..., so that your applications are easily portable

```jsx
kubectl create configmap configmap-name --from-literal=key=value --from-literal=key=value
kubectl get configmap configmap-name -o yaml

kubectl edit configmap configmap-name

kubectl create configmap configmap-name --from-file=file-path
kubectl delete configmap configmap-name
```

```jsx
kubectl create configmap my-config --from-literal=DATABASE_HOST=localhost --from-literal=DATABASE_PORT=5432

env:
name: DATABASE_HOST
valueFrom:
configMapKeyRef:
name: my-config
key: DATABASE_HOST
```

*Secrets*

A Secret is an object that contains a small amount of sensitive data such as a password, a token, or a key.

```jsx
kubectl create secret generic secret-name --from-literal=key=value --from-literal=key=value
kubectl create secret generic secret-name--from-file=file-path
kubectl get secret secret-name -o yaml
kubectl delete secret secret-name
```

For storing passwords and other sensitive data, consider using the `kubernetes.io/tls` type for Secrets.

```jsx
kubectl create secret generic my-secret --from-literal=DATABASE_PASSWORD=my-strong-password

env:
name: DATABASE_PASSWORD
valueFrom:
secretKeyRef:
name: my-secret
key: DATABASE_PASSWORD
restartPolicy: Never
```