kubernetes doc

Containerization & Orchestration/Kubernetes/workloads/10-Deployment-With-Services.md

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+### **1st Document: Namespace**
+
+```yaml
+apiVersion: v1
+```
+
+* Specifies the API version used. Here, it's version 1 of the core Kubernetes API.
+
+```yaml
+kind: Namespace
+```
+
+* Declares the resource type. This is a **Namespace**, which logically isolates groups of resources.
+
+```yaml
+metadata:
+  name: ns
+```
+
+* Metadata block.
+
+  * `name: ns` sets the name of the namespace to `ns`.
+
+---
+
+### **2nd Document: Service**
+
+```yaml
+---
+```
+
+* Separates multiple documents in the YAML file.
+
+```yaml
+apiVersion: v1
+```
+
+* Uses the core v1 API again.
+
+```yaml
+kind: Service
+```
+
+* Declares a **Service** resource, which provides stable networking to access pods.
+
+```yaml
+metadata:
+  name: nginx-service
+  namespace: ns
+  labels:
+    app: nginx
+```
+
+* Metadata block:
+
+  * `name: nginx-service`: name of the Service.
+  * `namespace: ns`: places this service in the previously created `ns` namespace.
+  * `labels`: key-value pairs used for organizing and selecting resources. Here, `app: nginx`.
+
+```yaml
+spec:
+  type: ClusterIP
+```
+
+* `spec` describes the behavior.
+
+  * `type: ClusterIP`: exposes the service internally within the cluster using a virtual IP.
+
+```yaml
+  selector:
+    app: nginx
+```
+
+* This selects pods with the label `app: nginx` to receive traffic from this service.
+
+```yaml
+  ports:
+    - name: http
+      port: 80
+      targetPort: 8080
+```
+
+* Defines port configuration:
+
+  * `name: http`: a name for the port (optional but useful for readability).
+  * `port: 80`: the port that the service exposes internally.
+  * `targetPort: 8080`: the port on the pod that receives the traffic.
+
+---
+
+### **3rd Document: Deployment**
+
+```yaml
+---
+```
+
+* Separates from the previous document.
+
+```yaml
+apiVersion: apps/v1
+```
+
+* Uses the `apps/v1` API group, suitable for deployments and other controllers.
+
+```yaml
+kind: Deployment
+```
+
+* Declares a **Deployment**, which ensures a specified number of pod replicas are running.
+
+```yaml
+metadata:
+  name: nginx-deployment
+  namespace: ns
+  labels:
+    app: nginx
+```
+
+* Metadata block:
+
+  * `name: nginx-deployment`: name of the deployment.
+  * `namespace: ns`: places this in the `ns` namespace.
+  * `labels: app: nginx`: used for matching with selectors.
+
+```yaml
+spec:
+  replicas: 2
+```
+
+* Desired number of pod replicas to run: 2.
+
+```yaml
+  selector:
+    matchLabels:
+      app: nginx
+```
+
+* Tells the deployment which pods to manage, by matching labels (`app: nginx`).
+
+```yaml
+  template:
+    metadata:
+      labels:
+        app: nginx
+```
+
+* Template for creating new pods:
+
+  * Each pod created will have `app: nginx` label.
+
+```yaml
+    spec:
+      containers:
+        - name: nginx
+          image: nginx:latest
+```
+
+* Pod spec:
+
+  * One container named `nginx`, using the latest official Nginx image.
+
+```yaml
+          ports:
+            - containerPort: 8080
+```
+
+* The container exposes port 8080 (must match the `targetPort` in the Service).
+
+```yaml
+          resources:
+            requests:
+              cpu: "100m"
+              memory: "128Mi"
+            limits:
+              cpu: "250m"
+              memory: "256Mi"
+```
+
+* **Resource management**:
+
+  * `requests`: the minimum guaranteed resources.
+
+    * `cpu: 100m` = 0.1 CPU core.
+    * `memory: 128Mi` = 128 MiB RAM.
+  * `limits`: the maximum resources the container can use.
+
+    * `cpu: 250m` = 0.25 CPU core.
+    * `memory: 256Mi` = 256 MiB RAM.
+