Add Dockerized Node.js application with PostgreSQL and Slack notifier

README.md

@@ -16,3 +16,6 @@
 # Part 5
 * [CI/CD with GitHub Action](./week5/CICD_with_GitHub_Actions.md)
 
+
+# Prat 6
+* [Docker-Containers](./week6/Docker-Containers.md)

week6/app/Dockerfile

@@ -0,0 +1,20 @@
+# Use the latest Node.js image as the base image
+FROM node:latest
+
+# Set the working directory inside the container
+WORKDIR /app
+
+# Copy package.json and package-lock.json (if present)
+COPY package*.json ./
+
+# Install the dependencies
+RUN npm install
+
+# Copy the rest of the application code
+COPY . .
+
+# Command to run the application
+CMD ["npm", "start"]
+
+# HEALTHCHECK instruction to monitor container health
+HEALTHCHECK --interval=30s --timeout=10s --retries=3 CMD curl -f http://localhost:3000 || exit 1

week6/app/index.js

@@ -0,0 +1,44 @@
+const { Client } = require('pg');
+const express = require('express');
+const morgan = require('morgan');
+
+const app = express();
+
+const connectionString = process.env.DATABASE_URL || 'postgres://myuser:mypassword@db:5432/mydb';
+
+const client = new Client({
+  connectionString: connectionString,
+});
+
+// Use morgan for HTTP request logging
+app.use(morgan('combined'));
+
+// Example route
+app.get('/', (req, res) => {
+  res.send('Hello, World!');
+});
+
+// Start the server
+const PORT = process.env.PORT || 3000;
+app.listen(PORT, () => {
+  console.log(`Server is running on port ${PORT}`);
+});
+
+async function checkDatabaseConnection() {
+  console.log(`Attempting to connect to database...`);
+  try {
+    await client.connect();
+    console.log('Successfully connected to PostgreSQL database!');
+    // const res = await client.query('SELECT NOW()');
+    // console.log('Current time from DB:', res.rows[0].now);
+  } catch (err) {
+    console.error('Error connecting to PostgreSQL database:', err.stack);
+    process.exit(1);
+  } 
+  // finally {
+  //   await client.end();
+  //   console.log('Database client disconnected.');
+  // }
+}
+
+checkDatabaseConnection();

week6/app/package.json

@@ -0,0 +1,14 @@
+{
+  "name": "node-postgres-app",
+  "version": "1.0.0",
+  "description": "Node.js app connecting to PostgreSQL in Docker",
+  "main": "index.js",
+  "scripts": {
+    "start": "node index.js"
+  },
+  "dependencies": {
+    "pg": "^8.0.0",
+    "express": "^4.18.2",
+    "morgan": "^1.10.0"
+  }
+}

week6/docker-compose.yml

@@ -0,0 +1,48 @@
+version: '3.8'
+
+services:
+  web:
+    build: ./app
+    ports:
+      - "8082:3000" # Changed host port from 8080 to 8081
+    environment:
+      - DATABASE_URL=postgres://myuser:mypassword@db:5432/mydatabase
+      # NODE_ENV: development # Example: if your app uses NODE_ENV
+    depends_on:
+      - db
+    networks:
+      - app-net
+
+  db:
+    image: postgres:latest
+    restart: always # Ensures the DB service attempts to restart if it fails
+    environment:
+      - POSTGRES_USER=myuser
+      - POSTGRES_PASSWORD=mypassword
+      - POSTGRES_DB=mydatabase
+    volumes:
+      - pgdata:/var/lib/postgresql/data # Persist database data in a named volume
+    networks:
+      - app-net
+    ports: # Optional: Expose PostgreSQL port to host for external tools (e.g., pgAdmin)
+      - "5432:5432" # Be cautious with exposing DB ports directly in production
+
+  slack-notifier:
+    build: ./slack-notifier
+    restart: always
+    volumes:
+      - /var/run/docker.sock:/var/run/docker.sock:ro # Mount Docker socket read-only
+    environment:
+      SLACK_WEBHOOK_URL: "https://hooks.slack.com/services/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"
+    logging: # Optional: configure logging for the notifier itself
+      driver: "json-file"
+      options:
+        max-size: "10m"
+        max-file: "3"
+
+networks:
+  app-net:
+    driver: bridge
+
+volumes:
+  pgdata: # Defines the named volume for data persistence

week6/hello-docker-app/.dockerignore

@@ -0,0 +1,22 @@
+
+# Exclude node_modules, as dependencies will be installed inside the container
+node_modules
+npm-debug.log
+
+# Exclude build artifacts or local development files
+build
+dist
+.env
+
+# Exclude version control directories and files
+.git
+.gitignore
+.gitattributes
+
+# Exclude Docker related files if they are in the context but not needed in image
+Dockerfile
+.dockerignore
+
+# Exclude OS-specific files
+.DS_Store
+Thumbs.db

week6/hello-docker-app/Dockerfile

@@ -0,0 +1,27 @@
+# Use the latest Node.js image as the base image
+FROM node:latest
+
+
+# Set the working directory inside the container
+WORKDIR /app
+
+
+# Copy package.json and package-lock.json to the working directory
+COPY package*.json ./
+
+
+# Install the dependencies
+RUN npm install
+
+
+# Copy the rest of the application code to the working directory
+COPY . .
+
+
+# Expose the port the app runs on
+EXPOSE 3000
+
+
+
+# Command to run the application
+CMD ["npm", "start"]

week6/hello-docker-app/index.js

@@ -0,0 +1,5 @@
+
+
+
+console.log("Hello from Docker");
+

week6/hello-docker-app/package.json

@@ -0,0 +1,11 @@
+{
+      "name": "hello-docker-app",
+      "version": "1.0.0",
+      "description": "Simple Node.js app for Docker",
+      "main": "index.js",
+      "scripts": {
+        "start": "node index.js"
+      },
+      "author": "",
+      "license": "ISC"
+    }

week6/slack-notifier/Dockerfile

@@ -0,0 +1,13 @@
+FROM alpine:latest
+
+# Install curl for sending notifications, jq for parsing JSON, and docker-cli for 'docker events'
+RUN apk add --no-cache curl jq docker-cli
+
+# Copy the notification script into the container
+COPY notify.sh /usr/local/bin/notify.sh
+
+# Make the script executable
+RUN chmod +x /usr/local/bin/notify.sh
+
+# Set the command to run the script
+CMD ["notify.sh"]

week6/slack-notifier/notify.sh

@@ -0,0 +1,65 @@
+#!/bin/sh
+
+# SLACK_WEBHOOK_URL is expected to be set as an environment variable
+
+if [ -z "$SLACK_WEBHOOK_URL" ]; then
+  echo "Error: SLACK_WEBHOOK_URL environment variable is not set."
+  exit 1
+fi
+
+echo "Slack Notifier started. Monitoring Docker events..."
+
+# Listen to Docker events. We are interested in container and health_status events.
+# Filters: type=container, and specific events like start, stop, die, health_status
+docker events --filter 'type=container' --filter 'event=start' --filter 'event=stop' --filter 'event=die' --filter 'event=health_status' --format '{{json .}}' | while read -r event_json
+do
+  # Ensure event_json is not empty
+  if [ -z "$event_json" ]; then
+    continue
+  fi
+
+  event_type=$(echo "$event_json" | jq -r '.Type')
+  action=$(echo "$event_json" | jq -r '.Action')
+  container_id=$(echo "$event_json" | jq -r '.Actor.ID')
+  container_name=$(echo "$event_json" | jq -r '.Actor.Attributes.name')
+  image_name=$(echo "$event_json" | jq -r '.Actor.Attributes.image')
+
+  # Construct message based on event action
+  message=""
+  if echo "$action" | grep -q "health_status:"; then
+    health_status_val=$(echo "$action" | cut -d' ' -f2) # Extracts 'healthy' or 'unhealthy'
+    message="🏥 Docker Health: Container \`$container_name\` (ID: \`${container_id:0:12}\`, Image: \`$image_name\`) is now \`$health_status_val\`."
+  elif [ "$action" = "die" ]; then
+    exit_code=$(echo "$event_json" | jq -r '.Actor.Attributes.exitCode')
+    message="💀 Docker Alert: Container \`$container_name\` (ID: \`${container_id:0:12}\`, Image: \`$image_name\`) has died with exit code \`$exit_code\`."
+  elif [ "$action" = "stop" ]; then
+    message="🛑 Docker Info: Container \`$container_name\` (ID: \`${container_id:0:12}\`, Image: \`$image_name\`) has stopped."
+  elif [ "$action" = "start" ]; then
+    message="🚀 Docker Info: Container \`$container_name\` (ID: \`${container_id:0:12}\`, Image: \`$image_name\`) has started."
+  else
+    # Skip other events not explicitly handled
+    echo "Skipping event: $action for $container_name"
+    continue
+  fi
+
+  if [ -n "$message" ]; then
+    echo "Preparing to send to Slack: $message"
+    # Construct JSON payload for Slack
+    json_payload=$(jq -n --arg text "$message" '{text: $text}')
+
+    # Send to Slack
+    # Adding -m 60 to set a maximum time for the curl operation to 60 seconds
+    # Adding --retry 3 and --retry-delay 5 for resilience
+    curl_response=$(curl -s -X POST -H 'Content-type: application/json' --data "$json_payload" "$SLACK_WEBHOOK_URL" -m 60 --retry 3 --retry-delay 5)
+
+    # Check if curl command itself failed (e.g., network issue before HTTP response)
+    if [ $? -ne 0 ]; then
+        echo "Error: curl command failed to execute."
+    # Check if Slack API returned "ok"
+    elif echo "$curl_response" | grep -q "ok"; then
+      echo "Successfully sent notification to Slack."
+    else
+      echo "Error sending notification to Slack. Response: $curl_response"
+    fi
+  fi
+done