How to write a web server (service) in OCaml?

Question

I want to write a web services server (using the http protocol) in OCaml.

For a simple example, I want to write http server . The user can access it and provide a parameter of the type http://myservice.com?i=1&j=2 . Then my server will receive the request and parameters and calculate i+j and return the result.

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Of course, my service will be more complicated for the calculation part. Instead of this simple calculation example, what I really need to do is

• database access (MongoDB) to retrieve data
• Access another third-party web service for more data.
• calculate all the data to get the result and return to the user.

So, I also need to consider parallelism / multi-threading , although first I want to start with a simple case.

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My questions:

• What library should I use to set up such an http server ? I reviewed Ocamlnet 3 and think it might be a good candidate, but it lacks a good tutorial, and I still don't know how to use nethttpd or netplex , etc.
• How do I build my web application architecture ? I know that OCaml is not suitable for parallelism , then how can I make each service instance not block?

Answer 1

Matias Giovannini has a good tutorial on how to do this in ocamlnet:

http://alaska-kamtchatka.blogspot.ca/2012/10/how-to-write-simple-web-application.html

Personally, I cannot stand ocamlnet, so I would look at cohttp. Ocamlnet is bigger, more mature and has more documents.

Answer 2

I think you should give Ocsigen a try.