Question 1

How do I start a Clack server from the command line?

Accepted Answer

First, install Roswell as per the README. Then, run 'ros install clack' to get the clackup script. Use 'clackup your-app.lisp' to start the server, which defaults to Hunchentoot on localhost:5000. Ensure your app.lisp file contains a lambda handler as shown in the examples.

Question 2

Clack vs Hunchentoot: which one should I use for my Common Lisp web app?

Accepted Answer

Clack is an abstraction layer that can use Hunchentoot as a backend. Choose Clack if you want server portability across multiple backends; use Hunchentoot directly if you need its specific features and don't mind being tied to a single server. Clack adds flexibility but may introduce slight overhead.

Question 3

Does Clack support WebSockets or real-time features?

Accepted Answer

Clack itself doesn't handle WebSockets, but some of its supported servers like Wookie do. You'll need to use server-specific extensions or middleware for WebSocket functionality, which may require additional setup and code outside Clack's core.

Question 4

How can I add routing to my Clack application?

Accepted Answer

Clack doesn't include built-in routing. You should use Lack, the Clack application builder mentioned in the README, or integrate other libraries like Caveman2. This involves defining routes separately and composing them with your Clack handlers.

Question 5

Is Clack suitable for building production REST APIs?

Accepted Answer

Yes, Clack's minimalist interface makes it good for REST APIs, but you'll need to handle aspects like JSON serialization and error handling manually or with extra libraries. Its server agnosticism helps in deployment, but ensure you test with your chosen backend for performance.

Question 6

What are the performance implications of using Clack's abstraction layer?

Accepted Answer

Clack adds a thin abstraction layer, so performance overhead is minimal in most cases. However, for high-throughput applications, direct server usage might offer slightly better performance. The trade-off is portability, which often outweighs the minor performance cost.

Question 7

Can I use Clack without Roswell for development?

Accepted Answer

Yes, you can load Clack via Quicklisp and run servers programmatically in Common Lisp, but the clackup command-line tool requires Roswell. For development without Roswell, you'll need to manage server startup manually through Lisp code, which is less convenient.

Clack

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