[TOC]
# Ingress
:::info
[Ingress | Kubernetes](https://kubernetes.io/docs/concepts/services-networking/ingress/)
:::

## Why we need Ingress?
- Each LoadBalancer service requires its own load balancer with its own public IP address
- Ingresses operate at the application layer of the network stack (HTTP) and can provide features such as cookie-based session affinity and the like, which services can’t.

## Install an Ingress Controller on Your Cluster
- [Ingress-Nginx Controller](https://kubernetes.github.io/ingress-nginx/deploy/)

kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/controller-v1.8.1/deploy/static/provider/cloud/deploy.yaml


- You can confirm if the Ingress controller is running:

kc get po --namespace=ingress-nginx


## Example: YAML Definition of Ingress Resources

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
    name: phoe-nginx-ingress
spec:
    rules:
    - host: phoebe.nginx.com
      http:
          paths:
          - path: /
            pathType: Prefix
            backend:
                service:
                  name: phoe-nginx-nodeport
                  port:
                    number: 8080

### Exposing multiple services through the same Ingress
#### MAPPING DIFFERENT SERVICES TO DIFFERENT PATHS OF THE SAME HOST

#### MAPPING DIFFERENT SERVICES TO DIFFERENT HOSTS

## Readiness Probes

- 在設定 container 相關腳本時，我們可以給予特定的指令，要求 K8s 透過該指令檢查 Pod 是否正確運行。
- 這些指令必須成功執行後 Pod 才會提供服務。

## Example: YAML Definition of Readiness Probes in Pods' YAML

apiVersion: v1
kind: Pod
metadata:
  name: phoe-nginx-pod
  labels:
    app: nginx
spec:
  containers:
  - name: phoe-nginx
    image: nginx:latest
    ports:
    - containerPort: 80
    readinessProbe:
      exec:
        command:
        - ls
        - /var/ready

kubectl exec phoe-nginx-pod -- touch /var/ready

- The readiness probe is checked periodically—every **10 seconds** by default.

:::warning
kubectl exec 指令中 namespace 欄位必須移到 -- command 前面才能成功執行
原本是 kubectl exec phoe-probe-pod -- touch /var/ready -n=phoebe-namespace
要改為 kubectl exec phoe-probe-pod -n=phoebe-namespace -- touch /var/ready
:::