caddy Interview Questions and Answers

1. What is Caddy?

   • Answer: Caddy is a powerful, open-source web server known for its automatic HTTPS, ease of use, and plugin-based architecture. It's written in Go and is designed to be fast, secure, and easy to configure.

2. What are the key advantages of using Caddy over other web servers like Apache or Nginx?

   • Answer: Caddy's advantages include automatic HTTPS provisioning (using Let's Encrypt), simplified configuration using a concise syntax, built-in support for various protocols and features, and a rapidly growing plugin ecosystem for extended functionality. It often boasts faster performance than its counterparts for specific use cases.

3. How does Caddy handle HTTPS automatically?

   • Answer: Caddy integrates with Let's Encrypt by default. When configured to serve HTTPS, it automatically obtains and manages SSL/TLS certificates, eliminating the manual process of certificate acquisition and renewal.

4. Explain Caddy's configuration file structure.

   • Answer: Caddy's configuration uses a structured JSON-like syntax, with blocks defining servers, listeners, routes, and other directives. This approach is generally considered more readable and maintainable than traditional configuration file formats.

5. What are Caddy's built-in features?

   • Answer: Caddy's built-in features include HTTP/1.1 and HTTP/2 support, load balancing, reverse proxy capabilities, static file serving, WebSocket support, and more. Many functionalities are enhanced or extended through its plugin system.

6. How do you install Caddy?

   • Answer: Installation methods vary by operating system. Common approaches include using a package manager (like apt on Debian/Ubuntu, brew on macOS), downloading a pre-built binary, or compiling from source. The Caddy website provides detailed installation instructions.

7. How do you configure Caddy to serve a static website?

   • Answer: A simple Caddyfile to serve a static website from the `public` directory would be: `root * /public`. This directs all requests to the `public` folder. More complex setups might involve specifying specific file types or using additional directives.

8. Explain Caddy's routing capabilities.

   • Answer: Caddy uses a powerful routing system to handle requests based on various criteria: path, method (GET, POST, etc.), headers, hostnames, and more. This allows for flexible and fine-grained control over how different requests are handled.

9. How do you use Caddy as a reverse proxy?

   • Answer: Using the `proxy` directive, you can configure Caddy to forward requests to an upstream server. This is essential for load balancing, protecting internal services, or adding features like caching and security.

10. What are Caddy plugins, and how do you use them?

    • Answer: Caddy plugins extend its functionality. They're added to the Caddyfile using the `import` directive, specifying the plugin's name and potentially configuration options. Plugins allow you to add features like authentication, logging, caching, and more.

11. How does Caddy handle load balancing?

    • Answer: Caddy can load balance requests across multiple upstream servers using various algorithms (e.g., round-robin, least connections). This ensures high availability and efficient distribution of traffic.

12. What is the difference between `root` and `file_server` directives?

    • Answer: `root` sets the base directory for serving static files. `file_server` is a more complete directive that includes additional options for fine-grained control over static file serving, such as setting headers or enabling directory listings.

13. How can you configure basic authentication with Caddy?

    • Answer: Basic authentication can be implemented using the `basicauth` directive, requiring users to provide a username and password before accessing protected resources.

14. How does Caddy handle caching?

    • Answer: Caddy can leverage caching mechanisms (e.g., using plugins or browser caching directives) to reduce server load and improve response times. This can significantly enhance performance for frequently accessed static content.

15. Explain Caddy's logging capabilities.

    • Answer: Caddy's logging features allow you to record access logs, error logs, and other events. You can customize the log format and destination (e.g., file, syslog). Plugins can further extend logging capabilities.

16. How can you configure Caddy to use a different port?

    • Answer: The port number is specified in the listener directive. For example, `listen 8080` will make Caddy listen on port 8080. The default port is 80 for HTTP and 443 for HTTPS.

17. How do you manage Caddy processes?

    • Answer: Depending on the installation method, Caddy process management can involve using systemd (Linux), launchd (macOS), or other process management tools. Caddy also offers options for graceful restarts and shutting down.

18. How can you deploy Caddy in a containerized environment (Docker)?

    • Answer: Official Caddy Docker images are readily available, simplifying deployment in Docker containers. You can configure the container to mount your Caddyfile and other necessary files.

19. What are some common Caddyfile directives?

    • Answer: Common directives include `listen`, `root`, `file_server`, `proxy`, `handle`, `rewrite`, `header`, `basicauth`, `tls`, and more. The specific directives needed will vary based on your application's requirements.

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