api21 Standalone API Engine

A high-performance standalone REST API engine built with Go (Golang). The frontend was moved to a separate repository, and this project serves exclusively as the API server.

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🚀 Architecture Overview

• Language & Framework: Go (v1.22+) powered by the Gin Web Framework.
• Database & ORM: PostgreSQL for relational data persistence managed via GORM.
• Caching & Limiter: Redis connection managing distributed sliding window rate limiting.
• Rate Limiting: Sliding window limiter (200 requests / 15 minutes per IP) applied to /api/ paths.
• Documentation: Interactive, responsive dark-themed API reference built directly into the server (accessible at the root /).
• Process Management: PM2 configuration managing the compiled Go binary.

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📁 Directory Structure

├── cmd/
│   └── app/
│       └── main.go         # Application bootstrap entrypoint
├── config/
│   └── config.go       # Environment variable parsing and loading
├── db/
│   └── db.go           # GORM connection and Postgres migrations
├── handlers/
│   ├── health.go       # Health probe handler (Postgres + Redis checks)
│   ├── health_test.go  # Route unit tests for health status
│   └── user.go         # User CRUD handlers (GORM integration)
├── middleware/
│   ├── cors.go         # CORS headers middleware for separate frontend repo
│   ├── logger.go       # Logger middleware
│   ├── ratelimit.go    # Redis-backed sliding window rate limiter
│   └── ssl.go          # HTTPS force redirect middleware
├── models/
│   └── user.go         # GORM database model schemas
├── redis/
│   └── redis.go        # Redis client pool and connectivity verification
├── services/
│   └── ping.go         # Background ping routine worker
├── static/
│   └── index.html      # Glassmorphic interactive API documentation page
├── ecosystem.config.cjs # PM2 ecosystem configuration for Go binary
└── go.mod / go.sum     # Go dependency manager manifest files

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🛠️ Installation & Setup

1. Configure Environment Variables: Create a .env file in the root directory:

   PORT=3000
   GO_ENV=development
   DATABASE_URL=postgres://postgres:postgres@127.0.0.1:5432/api21?sslmode=disable
   REDIS_URL=redis://localhost:6379/0
   PING_URL=

2. Download dependencies:

   go mod tidy

3. Run Locally in Dev Mode:

   • Standard run:

     go run cmd/app/main.go

   • Live auto-reload (using installed air watcher):

     # Add ~/go/bin to path if needed
     export PATH=$PATH:~/go/bin
     air

   Open http://localhost:8080 to view the interactive API Documentation sandbox.

4. Run Local Tests:

   go test ./...

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📦 Production Deployment (Systemd on EC2)

🔑 GitHub Actions Secrets Setup

To enable automated CI/CD deployment via GitHub Actions, add the following Secrets under your GitHub repository (Settings > Secrets and variables > Actions > New repository secret):

Secret Name	Description / How to Get It
SERVER_HOST	The Public IPv4 Address or DNS name of your EC2 instance. • How to get: In your AWS EC2 Console, select your active instance and copy the Public IPv4 address or Public IPv4 DNS from the Instance Details tab.
SERVER_USER	The SSH login user for the EC2 instance. • How to get: Depends on the AMI you launched your instance with. Typical default users are: - Ubuntu: ubuntu - Amazon Linux 2 / 2023: ec2-user - Debian: admin - CentOS: centos
SSH_PRIVATE_KEY	The private key (.pem) used to authenticate with your EC2 instance. • How to get: Locate the Key Pair file (.pem) you created/downloaded when launching the EC2 instance. Open this file in any raw text editor, copy its entire contents (including headers -----BEGIN RSA PRIVATE KEY----- and -----END RSA PRIVATE KEY-----), and paste it as the secret value.

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⚙️ EC2 Manual Setup Guide

Deploy the Go binary using native Linux systemd to ensure automatic restarts and robust logging without requiring Node.js/PM2.

1. Compile Go Binary:

   CGO_ENABLED=0 GOOS=linux GOARCH=arm64 go build -o bin/api21_server cmd/app/main.go

2. Configure Environment Variables on EC2: Create a .env file in the working directory on your EC2 instance (/home/ubuntu/api21/.env) with your production variables:

   PORT=8080
   GO_ENV=production
   DATABASE_URL=postgres://<db_user>:<db_password>@<db_host>:5432/<db_name>?sslmode=require
   REDIS_URL=redis://localhost:6379/0
   MASTER_CREDENTIALS=admin:securepassword
   ADMIN_ORIGIN=https://admin.yourdomain.com

3. Create Systemd Service: Create a file at /etc/systemd/system/api21.service:

   [Unit]
   Description=api21 Go Backend Service
   After=network.target postgresql.service redis.service
   
   [Service]
   User=ubuntu
   Group=ubuntu
   WorkingDirectory=/home/ubuntu/api21
   ExecStart=/home/ubuntu/api21/bin/api21_server
   Restart=always
   RestartSec=5s
   
   # Standard Output/Error is automatically captured by journald
   StandardOutput=syslog
   StandardError=syslog
   SyslogIdentifier=api21
   
   [Install]
   WantedBy=multi-user.target

4. Start and Enable Service:

   sudo systemctl daemon-reload
   sudo systemctl enable api21.service
   sudo systemctl start api21.service

5. Check Logs:

   sudo journalctl -u api21.service -f

6. Configure and Reload Nginx Reverse Proxy: To support reverse proxying HTTP requests and WebSocket connections (for the WebTerminal dashboard feature), merge the configuration from nginx.conf.example into your Nginx site configuration, and then run the following commands to test and apply the configuration:

   # Test the configuration file for syntax errors
   sudo nginx -t
   
   # Reload Nginx to apply changes (keeps existing connections alive)
   sudo systemctl reload nginx