Add ruby equivalent of node.js app

lessons/222/ruby-app-node-equivalent/.dockerignore

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+# Logs
+logs
+*.log
+
+# Runtime data
+pids
+*.pid
+*.seed
+
+# Directory for instrumented libs generated by jscoverage/JSCover
+lib-cov
+
+# Coverage directory used by tools like istanbul
+coverage
+
+# Grunt intermediate storage (http://gruntjs.com/creating-plugins#storing-task-files)
+.grunt
+
+# node-waf configuration
+.lock-wscript
+
+# Compiled binary addons (http://nodejs.org/api/addons.html)
+build/Release
+
+# Dependency directory
+# https://www.npmjs.org/doc/misc/npm-faq.html#should-i-check-my-node_modules-folder-into-git
+node_modules
+
+server/*.spec.js
+kubernetes
+
+# Don't copy default config
+config.yaml
+
+# Ruby specific
+*.gem
+*.rbc
+.bundle
+.config
+coverage
+InstalledFiles
+lib/bundler/man
+pkg
+rdoc
+spec/reports
+test/tmp
+test/version_tmp
+tmp
+.bundle/
+vendor/bundle
+Gemfile.lock
+

lessons/222/ruby-app-node-equivalent/Dockerfile

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+FROM ruby:3.3-bookworm AS build
+
+COPY . /app
+
+WORKDIR /app
+
+RUN bundle install
+
+FROM ruby:3.3-slim-bookworm
+
+COPY --from=build /app /app
+COPY --from=build /usr/local/bundle /usr/local/bundle
+
+WORKDIR /app
+
+CMD ["ruby", "app.rb"]
+

lessons/222/ruby-app-node-equivalent/Gemfile

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+# frozen_string_literal: true
+
+source 'https://rubygems.org'
+
+gem 'pg'
+gem 'prometheus-client'
+gem 'rack'
+gem 'yaml'
+

lessons/222/ruby-app-node-equivalent/Gemfile.lock

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+GEM
+  remote: https://rubygems.org/
+  specs:
+    base64 (0.3.0)
+    pg (1.6.2)
+    pg (1.6.2-aarch64-linux)
+    pg (1.6.2-aarch64-linux-musl)
+    pg (1.6.2-arm64-darwin)
+    pg (1.6.2-x86_64-darwin)
+    pg (1.6.2-x86_64-linux)
+    pg (1.6.2-x86_64-linux-musl)
+    prometheus-client (4.2.5)
+      base64
+    rack (3.2.4)
+    yaml (0.4.0)
+
+PLATFORMS
+  aarch64-linux
+  aarch64-linux-musl
+  arm64-darwin
+  ruby
+  x86_64-darwin
+  x86_64-linux
+  x86_64-linux-musl
+
+DEPENDENCIES
+  pg
+  prometheus-client
+  rack
+  yaml
+
+BUNDLED WITH
+   2.7.2

lessons/222/ruby-app-node-equivalent/README.md

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+# Ruby Device Management API
+
+A Ruby-based HTTP server application for managing IoT devices with PostgreSQL database integration and Prometheus metrics. This is a Ruby equivalent of the Node.js application in the `node-app` folder.
+
+## Overview
+
+This application provides a RESTful API for managing device records, including:
+- Device listing and creation
+- PostgreSQL database integration
+- Prometheus metrics for monitoring
+- Health check endpoint
+
+## Features
+
+- **HTTP Server**: Built with Rack and WEBrick
+- **Database**: PostgreSQL integration using the `pg` gem
+- **Metrics**: Prometheus histogram metrics for tracking database operation duration
+- **RESTful API**: Endpoints for device management
+- **Docker Support**: Multi-stage Dockerfile for containerized deployment
+
+## Prerequisites
+
+- Ruby 3.3 or higher
+- PostgreSQL database
+- Bundler gem (usually comes with Ruby)
+
+## Installation
+
+1. Install dependencies:
+```bash
+bundle install
+```
+
+## Configuration
+
+The application uses a `config.yaml` file for configuration. Create or modify `config.yaml`:
+
+```yaml
+---
+appPort: 8080
+db:
+  user: node
+  password: devops123
+  host: postgresql.antonputra.pvt
+  database: mydb
+  maxConnections: 75
+```
+
+**Note**: Update the database connection details to match your PostgreSQL setup.
+
+## Running the Application
+
+### Local Development
+
+1. Ensure PostgreSQL is running and accessible
+2. Make sure the database and `node_device` table exist (see migration notes below)
+3. Start the server:
+```bash
+ruby app.rb
+```
+
+The server will start on `http://0.0.0.0:8080` (or the port specified in `config.yaml`).
+
+### Using Docker
+
+1. Build the Docker image:
+```bash
+docker build -t ruby-app-node-equivalent .
+```
+
+2. Run the container:
+```bash
+docker run -p 8080:8080 ruby-app-node-equivalent
+```
+
+## API Endpoints
+
+### GET /api/devices
+
+Returns a list of sample devices.
+
+**Response:**
+```json
+[
+  {
+    "id": 1,
+    "uuid": "9add349c-c35c-4d32-ab0f-53da1ba40a2a",
+    "mac": "5F-33-CC-1F-43-82",
+    "firmware": "2.1.6",
+    "created_at": "2024-05-28T15:21:51.137Z",
+    "updated_at": "2024-05-28T15:21:51.137Z"
+  },
+  ...
+]
+```
+
+### POST /api/devices
+
+Creates a new device in the database.
+
+**Request Body:**
+```json
+{
+  "mac": "AA-BB-CC-DD-EE-FF",
+  "firmware": "1.0.0"
+}
+```
+
+**Response (201 Created):**
+```json
+{
+  "id": 4,
+  "uuid": "generated-uuid",
+  "mac": "AA-BB-CC-DD-EE-FF",
+  "firmware": "1.0.0",
+  "created_at": "2024-11-08T12:34:56.789Z",
+  "updated_at": "2024-11-08T12:34:56.789Z"
+}
+```
+
+**Error Response (400 Bad Request):**
+```json
+{
+  "message": "Error message"
+}
+```
+
+### GET /metrics
+
+Returns Prometheus metrics in text format. This endpoint exposes the `myapp_request_duration_seconds` histogram metric that tracks database operation durations.
+
+### GET /healthz
+
+Health check endpoint. Returns `OK` if the server is running.
+
+**Response:**
+```
+OK
+```
+
+## Database Schema
+
+The application expects a PostgreSQL table named `node_device` with the following structure:
+
+```sql
+CREATE TABLE node_device (
+  id SERIAL PRIMARY KEY,
+  uuid VARCHAR(255) NOT NULL,
+  mac VARCHAR(255) NOT NULL,
+  firmware VARCHAR(255) NOT NULL,
+  created_at TIMESTAMP NOT NULL,
+  updated_at TIMESTAMP NOT NULL
+);
+```
+
+## Project Structure
+
+```
+ruby-app-node-equivalent/
+├── app.rb           # Main HTTP server application
+├── config.rb        # Configuration loader
+├── config.yaml      # Configuration file
+├── db.rb            # PostgreSQL database connection
+├── devices.rb       # Device database operations
+├── metrics.rb       # Prometheus metrics setup
+├── Gemfile          # Ruby dependencies
+├── Dockerfile       # Docker build configuration
+├── .dockerignore    # Docker ignore patterns
+└── README.md        # This file
+```
+
+## Dependencies
+
+- **pg**: PostgreSQL database adapter
+- **prometheus-client**: Prometheus metrics client library
+- **rack**: Web server interface
+- **yaml**: YAML configuration parsing (built-in)
+
+## Metrics
+
+The application tracks database operation duration using a Prometheus histogram metric:
+
+- **Metric Name**: `myapp_request_duration_seconds`
+- **Type**: Histogram
+- **Labels**: `op` (operation type, e.g., "db")
+- **Buckets**: Custom buckets optimized for low-latency operations (0.00001 to 17.5 seconds)
+
+## Error Handling
+
+- Database errors are caught and returned as 400 Bad Request with an error message
+- Invalid JSON in POST requests will result in a 400 error
+- All errors are logged to stdout
+
+## Notes
+
+- The server uses a 60-second keep-alive timeout
+- UUIDs are automatically generated using Ruby's `SecureRandom.uuid`
+- Timestamps are generated in ISO 8601 format with millisecond precision
+- The application uses a single PostgreSQL connection (connection pooling can be added if needed)
+