144 lines
2.5 KiB
Markdown
144 lines
2.5 KiB
Markdown
# 🔗 **Kubernetes Services (SVC)**
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A **Service** in Kubernetes provides a stable network endpoint to access a set of Pods. It abstracts access through selectors and DNS names, enabling loose coupling between client applications and Pods.
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---
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## 🌐 **Service Basics**
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### 📌 **Service Flow**
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```
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Service ➡️ Endpoint ➡️ Pods
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```
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* Services **group Pods** behind a single access point.
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* They get a **cluster-wide DNS name** automatically.
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* Use **label selectors** to forward traffic to matching Pods.
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---
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## 🧭 **Types of Services**
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1. **ClusterIP** (default)
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* Only reachable within the cluster.
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2. **NodePort**
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* Exposes the service via a static port on each node.
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3. **LoadBalancer**
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* Creates an external IP address using a cloud provider.
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---
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## 🧪 **Useful Commands**
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### 🔍 Get Endpoints
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```bash
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kubectl get ep -n <namespace>
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```
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### 📄 Get Services
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```bash
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kubectl get svc -n <namespace>
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```
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```bash
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kubectl expose deployment web-server-dep -n dev --port 80
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```
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---
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## 🔁 **Port Forwarding**
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To access a service from your local machine, forward a local port to the service port:
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```bash
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kubectl port-forward -n <namespace> svc/<service-name> <local-port>:<target-port>
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```
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> **Example:**
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> Forward local port `8080` to port `80` of `my-service` in the `mynamespace` namespace:
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>
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> ```bash
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> kubectl port-forward -n mynamespace svc/my-service 8080:80
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> ```
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You can also bind to all network interfaces:
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```bash
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kubectl port-forward -n <namespace> svc/nginx 80:80 --address 0.0.0.0
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```
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> 🌐 **DNS format:**
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> `<service-name>.<namespace>.svc.cluster.local`
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---
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## 🧾 **Example Service Manifest**
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```yaml
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apiVersion: v1
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kind: Service
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metadata:
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name: nginx
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namespace: ns
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labels:
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app: web-server
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spec:
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type: ClusterIP # Options: ClusterIP, NodePort, LoadBalancer
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selector:
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app: nginx
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ports:
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- name: http
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port: 80
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targetPort: 8080
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```
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> 🔍 **Note:** The `selector` must match the labels of the target Pods.
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> 🧠 **Tip:** Use `kubectl describe svc <service-name>` to inspect the service and verify connectivity.
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```yaml
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apiVersion: v1
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kind: Service
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metadata:
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name: nginx
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namespace: ns
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labels:
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app: web-server
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spec:
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type: LoadBalancer
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selector:
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app: nginx
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ports:
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- name: http
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port: 80
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targetPort: 8080
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```
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```yaml
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apiVersion: v1
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kind: Service
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metadata:
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name: db-svc
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namespace: db
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spec:
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type: NodePort
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ports:
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- name: sql
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port: 3306
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targetPort: 3306
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nodePort: 30000
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selector:
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app: db
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``` |