qvest-task/docs/diagrams/application-stack.md

Application Stack Diagram

This diagram shows the Docker containers running on the EC2 instance and their relationships.

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graph TB
    User([User])
    LetsEncrypt[Let's Encrypt<br/>SSL Certs]
    
    subgraph EC2["EC2 Instance"]
        subgraph Docker["Docker Compose"]
            Nginx[Nginx<br/>Port 80, 443]
            Gitea[Gitea<br/>Port 3000, 2222]
            Postgres[(PostgreSQL<br/>Port 5432)]
            Certbot[Certbot<br/>SSL Renewal]
            DIUN[DIUN<br/>Update Monitor]
            
            Nginx -->|Reverse Proxy| Gitea
            Gitea -->|Database Connection| Postgres
            DIUN -.->|Monitors for Updates| Nginx
            DIUN -.->|Monitors for Updates| Gitea
            DIUN -.->|Monitors for Updates| Postgres
            Certbot -.->|Renews Certificates| Nginx
        end
        
        subgraph Systemd["Systemd Services"]
            Runner1[act_runner-1<br/>CI/CD Runner]
            Runner2[act_runner-2<br/>CI/CD Runner]
            
            Runner1 -.->|Executes Workflows| Gitea
            Runner2 -.->|Executes Workflows| Gitea
        end
    end
    
    User -->|HTTPS| Nginx
    User -->|Git SSH| Gitea
    LetsEncrypt -.->|Certificate Authority| Certbot
    
    style EC2 fill:#e5e7eb,stroke:#4b5563,stroke-width:2px,stroke-dasharray: 5 5
    style Docker fill:#d1d5db,stroke:#4b5563,stroke-width:2px,stroke-dasharray: 5 5
    style Systemd fill:#d1d5db,stroke:#4b5563,stroke-width:2px,stroke-dasharray: 5 5
    
    style Nginx fill:#10B981,stroke:#333,stroke-width:1px,color:#fff
    style Gitea fill:#3B82F6,stroke:#333,stroke-width:1px,color:#fff
    style Postgres fill:#8B5CF6,stroke:#333,stroke-width:1px,color:#fff
    style DIUN fill:#F59E0B,stroke:#333,stroke-width:1px,color:#fff
    style Certbot fill:#6366F1,stroke:#333,stroke-width:1px,color:#fff
    style Runner1 fill:#EF4444,stroke:#333,stroke-width:1px,color:#fff
    style Runner2 fill:#EF4444,stroke:#333,stroke-width:1px,color:#fff

Components

Docker Containers

• Nginx: Reverse proxy handling SSL termination and routing to Gitea
• Gitea: Git server application with Actions enabled (HTTP: 3000, SSH: 2222)
• PostgreSQL: Database storing repositories metadata, users, issues
• DIUN: Monitors Docker Hub for image updates, sends email notifications
• Certbot: Handles Let's Encrypt SSL certificate renewal

Systemd Services

• act_runner-1: First Gitea Actions runner for CI/CD workflows
• act_runner-2: Second Gitea Actions runner for CI/CD workflows

Container Communication

• All containers in the same Docker network (gitea-network)
• Nginx proxies HTTPS requests to Gitea's internal port 3000
• Gitea connects to PostgreSQL via container name (postgres)
• DIUN monitors containers based on labels (diun.enable=true)
• Certbot shares volumes with nginx for certificate storage
• Runners connect to Gitea via http://localhost:3000

Data Persistence

Docker volumes ensure data survives container restarts:

• gitea-data: Git repositories and uploads
• gitea_postgres-data: PostgreSQL database files
• certbot-etc: Let's Encrypt certificates
• certbot-var: Certbot working directory
• web-root: ACME challenge files for SSL verification