Add tech_docs/kubernetes.md

2024-06-26 23:40:00 +00:00
parent c14a288a40
commit b7d57dc64a
1 changed files with 139 additions and 0 deletions
--- a/tech_docs/kubernetes.md
+++ b/tech_docs/kubernetes.md
@@ -0,0 +1,139 @@
+Certainly! I'll simplify the project and provide clearer documentation for both the Docker Compose and Kubernetes approaches. We'll use a simple web application with a Redis cache as our example.
+
+Let's start with the Docker Compose version:
+
+
+
+```yaml
+version: '3'
+
+services:
+  # Web application service
+  web:
+    image: nginx:alpine  # Using the official Nginx image
+    ports:
+      - "80:80"  # Mapping host port 80 to container port 80
+    environment:
+      - REDIS_HOST=redis  # Environment variable to connect to Redis
+    depends_on:
+      - redis  # Ensures redis service is started before web
+
+  # Redis cache service
+  redis:
+    image: redis:alpine  # Using the official Redis image
+    ports:
+      - "6379:6379"  # Exposing Redis port (usually not needed in production)
+
+# No volumes defined for simplicity
+
+```
+
+Now, let's create the equivalent setup using Kubernetes resources:
+
+
+
+```yaml
+---
+# Web application deployment
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: web
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: web
+  template:
+    metadata:
+      labels:
+        app: web
+    spec:
+      containers:
+      - name: web
+        image: nginx:alpine
+        ports:
+        - containerPort: 80
+        env:
+        - name: REDIS_HOST
+          value: redis  # Points to the Redis service name
+
+---
+# Web application service (for external access)
+apiVersion: v1
+kind: Service
+metadata:
+  name: web
+spec:
+  selector:
+    app: web
+  ports:
+  - port: 80
+    targetPort: 80
+  type: LoadBalancer  # Exposes the service externally
+
+---
+# Redis deployment
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: redis
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: redis
+  template:
+    metadata:
+      labels:
+        app: redis
+    spec:
+      containers:
+      - name: redis
+        image: redis:alpine
+        ports:
+        - containerPort: 6379
+
+---
+# Redis service (for internal access)
+apiVersion: v1
+kind: Service
+metadata:
+  name: redis
+spec:
+  selector:
+    app: redis
+  ports:
+  - port: 6379
+
+```
+
+Now, let me explain the key differences and similarities between these two approaches:
+
+1. Structure:
+   - Docker Compose: All services are defined in a single YAML file.
+   - Kubernetes: Resources are typically split into separate YAML files (combined here for simplicity).
+
+2. Service Definition:
+   - Docker Compose: Services are defined under the `services` key.
+   - Kubernetes: Services are split into Deployments (for container specs) and Services (for networking).
+
+3. Networking:
+   - Docker Compose: Uses the `ports` key to map container ports to host ports.
+   - Kubernetes: Uses Service resources to expose deployments, with `LoadBalancer` type for external access.
+
+4. Environment Variables:
+   - Docker Compose: Directly specified under the `environment` key.
+   - Kubernetes: Defined in the container spec under the `env` key.
+
+5. Dependencies:
+   - Docker Compose: Uses `depends_on` to specify service dependencies.
+   - Kubernetes: Doesn't have a direct equivalent; often handled through readiness probes or init containers (not shown in this simple example).
+
+6. Scaling:
+   - Docker Compose: Typically runs on a single host, limiting scaling options.
+   - Kubernetes: Can easily scale by changing the `replicas` field in Deployments.
+
+Both configurations achieve the same basic setup: a web service connected to a Redis cache. The Kubernetes version offers more flexibility for scaling and managing the application across multiple nodes, while the Docker Compose version is simpler for local development or single-host deployments.
+
+Would you like me to elaborate on any specific aspect of these configurations?