Question

[This will only make sense if you’ve seen Kevin Smith’s ‘Erlang in Practice’ screencasts]

I’m an Erlang noob trying to build a simple Erlang/OTP system with embedded webserver [mochiweb].

I’ve walked through the EIP screencasts, and I’ve toyed with simple mochiweb examples created using the new_mochiweb.erl script.

I’m trying to figure out how the webserver should relate to the gen_server modules. In the EIP examples [Ch7], the author creates a web_server.erl gen_server process and links the mochiweb_http process to it. However in a mochiweb project, the mochiweb_http process seems to be ‘standalone’; it doesn’t seem to be embedded in a separate gen_server process.

My question is, should one of these patterns be preferred over the other ? If so, why ? Or doesn’t it matter ?

Thanks in advance.

Answer 1

The reason to embed a process in a supervision tree is so that you can restart it if it fails.

A process that handles an HTTP request is responding to an event generated externally – in a browser. It is not possible to restart it – that is the prerogative of the person running the browser – therefore it is not necessary to run it under OTP – you can just spawn it without supervision.